Apple has announced that macOS 26 Tahoe will be released on Monday 15 September, slightly earlier than had been speculated. Even if you’re not intending to upgrade to that, you might instead be looking at moving from Sonoma to Sequoia, or perhaps dragging your feet and considering Sonoma as it enters its final year of support. This article considers what you should do when preparing to upgrade macOS.

One of the surgeons I worked for in my first internship in hospital taught me an important lesson in life: when considering the outcome of anything that could go wrong, assume that it will go wrong, and prepare for that. When it actually works out better than you planned for, you can enjoy your success.

Emergencies

The worst case is that your Mac dies during the upgrade. Although that’s also the least likely, you need to think through your disaster plan. I ensure that all my most essential files and data are shared or copied up to iCloud so that I could get by for a day or three without that Mac. A recent full backup is also essential: if your Mac needs to go away to be resuscitated, one way or another that’s what you’ll be restoring from.

Upgrades do bring a tiny but significant risk of bricking your Mac in a way that only a full Restore will recover it. Although this can apply to Intel Macs with T2 chips if a T2 firmware update goes wrong, this is more the preserve of Apple silicon Macs. I’ve recently stepped through your options with full details here. Your first DFU Restore is daunting, but once you’ve done one, you’ll realise that they’re not that challenging if you have the right cable and DFU port. When you’ve restored firmware and macOS, you’ll then be restoring from that last backup, emphasising its importance.

In the days before the SSV, when there was only one boot volume and that could so readily be corrupted during upgrades, you also needed to have an emergency toolkit handy to repair an upgrade that went wrong. These days, the whole of the System in the SSV is either perfect, or macOS has to be reinstalled. Minor glitches are almost invariably corrected by restarting after the upgrade has completed, or starting up in Safe mode (remember on Apple silicon Macs that’s performed from Recovery).

Reverting macOS

The other possibility that you should plan for is beating a hasty retreat and reverting to an older version of macOS. Provided that you’re fully aware of the changes to the macOS interface brought in Tahoe, I think this is less likely for those upgrading from Sequoia, but if you’re skipping a version or two you could still find yourself unable to use a vital peripheral or one of your key apps, leaving you with reversion as your only option.

I’m sometimes asked by eternal optimists whether you can revert to your previous macOS simply by using its SSV snapshot. Sadly, snapshots are of no help: the only way back is to wipe and reinstall that macOS.

On Intel Macs, you’ll need to do this when booted from an external bootable installer, which doesn’t have to be on a USB ‘thumb’ drive, but does still require its own HFS+ volume to work. Apple explains this here, and Mr. Macintosh has links to all available installer apps.

Although you can do that with an Apple silicon Mac, if you have a second Mac and the right USB-C cable, it’s usually quicker and simpler to do this by restoring from the appropriate IPSW file in DFU mode, then restoring your files from your latest backup, as explained here. This is particularly valuable, as it also restores the original firmware, which may be the root of your problems. Unfortunately, that doesn’t seem possible with Intel Macs. Once their firmware has been upgraded, the user isn’t able to downgrade it.

Checklist

• Check you’re prepared to use your disaster plan if needed.
• Consider sharing and copying to iCloud to help you use another Mac or device temporarily.
• Make a full backup immediately before starting the upgrade.
• Restart, or start up in Safe mode, if the upgrade leaves your Mac with problems.
• Reverting to an older macOS isn’t trivial, and will require you to restore from your backup.
• Revert an Intel Mac using a bootable external installer.
• Consider reverting an Apple silicon Mac by restoring it in DFU mode, using an older IPSW.

Whatever you choose to do, I wish you success, and hope that your preparations prove completely unnecessary.

Apple has just released its weekly update to XProtect for all supported versions of macOS, bringing it to version 5314. As usual, Apple doesn’t release information about what security issues this update might add or change.

This version brings no changes in its text data files, specifically its Yara rules. Wondering if I might be missing something, I have also compared the general release XProtect files with those for Sequoia and Tahoe (delivered by iCloud), and they are identical too.

You can check whether this update has been installed by opening System Information via About This Mac, and selecting the Installations item under Software.

A full listing of security data file versions is given by SilentKnight and SystHist for El Capitan to Tahoe available from their product page. If your Mac hasn’t yet installed this update, you can force it using SilentKnight or at the command line.

If you want to install this as a named update in SilentKnight, its label is XProtectPlistConfigData_10_15-5314

Sequoia and Tahoe systems only

This update has already been released for Sequoia and Tahoe via iCloud. If you want to check it manually, use the Terminal command
sudo xprotect check
then enter your admin password. If that returns version 5314 but your Mac still reports an older version is installed, you may be able to force the update using
sudo xprotect update

The Dutch Golden Age brought the rapid development of painting genres such as still life, but its most explosive growth was in those depicting everyday life, from interiors showing domestic activities to maritime views. This article introduces some of those new themes.

Painting scenes of ordinary people undertaking the activities of everyday life, commonly if unhelpfully known as genre painting, was one of the most popular through this period.

Gerard ter Borch’s The Spinner from about 1655 is a fine example with its outstanding rendering of the properties of its different surfaces. Seated at her spinning loom in front of her bed, and with her lapdog in place, this ordinary woman is doing what she did as a matter of routine. Ter Borch’s life and career were based in the Dutch Republic, but he also travelled across Europe, and was even honoured with a knighthood when he was working in Madrid.

Jan Vermeer is now best known for his series of paintings of middle-class women in rooms in his house, lit from the windows on the left of the painting. However, he also painted two remarkable works showing the world outside his house in the city of Delft: this townscape of a street and its occupants in The Little Street above, and the View of Delft waterfront below.

The Republic’s thriving cities, where its artists had their workshops, became the focus of a novel type of landscape depicting their buildings and open spaces, instead of trees and fields.

Gerrit Berckheyde’s view of Groote Market in Haarlem from 1673 shows one the largest of the city’s marketplaces at the close of the Golden Age. He was based in this city, which he documented extensively in his cityscapes.

The Republic had a long shoreline, extensive rivers and canals, and the huge enclosed body of water Zuiderzee. Its merchant and military navies were among the largest of the time. Inevitably, water became a substantial part of Dutch painting, and seascapes were another novel development.

Jan van Goyen’s View of Dordrecht with the Grote Kirk Across the Maas (1644) shows a skyline dominated by the still-unfinished 65 metre tower of the Grote Kerk, built between 1285-1470. At the edges of the city are several windmills, which were already associated with the Republic. Van Goyen studied in Haarlem, then set up his studio in The Hague.

Meindert Hobbema’s view of The Haarlem Lock, Amsterdam from 1663-65 is a good example of a working lock with a raising bridge, showing the masts of many ships in the harbour beyond. A pupil of Jacob van Ruisdael, Hobbema was based in Amsterdam throughout his life.

The great masters of Dutch landscape art like Jacob van Ruisdael must have painted many hundreds of windmills, of which one of the best-known is this view of The Windmill at Wijk bij Duurstede from about 1670. This small town, now a city, is on the bank of the River Rhine, an ideal location for delivering grain by barge, and shipping the resulting flour. Van Ruisdael trained and started his career in Haarlem, then moved to Amsterdam.

With its long coastline and sandy beaches, the Republic was probably the birthplace of the beachscape.

Among Adriaen van de Velde’s earliest surviving paintings are several beach scenes, including The Beach at Scheveningen (1658), which are exceptional for someone who was only twenty-one at the time. Despite the dress and wagons, this has a timeless quality, and gives the most wonderful impression of light and space. Scheveningen is part of the coast of The Hague, although this artist worked in Amsterdam.

More traditional landscapes were adapted to cope with the flat land, and their emphasis shifted to the clouds above.

Under the clouds of Philip de Koninck’s Distant View With Cottages Along a Road (1655), a lone man sits by a pond at the lower right. Behind him a rutted road runs past cottages, down towards a bridge over a river and two towns beyond. The land forms a minority of the view, though, as most of it is cloud. De Koninck was another lifelong resident of Amsterdam.

The Golden Age coincided with a cold phase in the climate, the Little Ice Age, with 1650 the start of its coldest period. Dutch landscapes took advantage of the icy scenes each winter.

Aert van der Neer’s beautifully-lit Sports on a Frozen River (c 1660) includes several who are playing colf, an antecedent of golf which was also played during the warmer months, but was most distinctively played on frozen rivers and canals. This artist also lived in Amsterdam.

Perhaps inevitably, the Dutch Republic profited well from those harsh winters, its merchants doing a thriving trade exporting food to countries whose crops had failed because of the cold weather. Dutch artists appear to have done likewise, and their paintings of winter are now found across Europe, and remain popular on Christmas cards.

Why is it that a fast Apple silicon Mac takes so long to tar and Gzip a large folder? Surely, with all those fast Performance cores, even GB should be compressed in the twinkling of an eye? Could it be that macOS is running the tar command on its Efficiency cores instead, eking out the power? This article explores and explains how macOS sets the priority for command tools and similar binaries.

Threads

There are two key factors at work here. The first is threading, division of the work done by a process into single flows of execution run on one CPU core at a time. Every process has its main thread, and many can also create additional threads that can be scheduled to run in parallel. While macOS can and often will move threads around its cores, a single-threaded process can only run on a single CPU core at a time.

QoS

macOS also allocates threads to cores. Although neither you nor the process control that absolutely, processes can influence it by setting a Quality of Service, QoS, for each of their threads. QoS is chosen from the standard list:

• QoS 9 (binary 001001), named background and intended for threads performing maintenance, which don’t need to be run with any higher priority.
• QoS 17 (binary 010001), utility, for tasks the user doesn’t track actively.
• QoS 25 (binary 011001), userInitiated, for tasks that the user needs to complete to be able to use the app.
• QoS 33 (binary 100001), userInteractive, for user-interactive tasks, such as handling events and the app’s interface.

There’s also a ‘default’ value between 17 and 25, an unspecified value, and you might come across others used by macOS.

If all your Mac’s CPU cores are free and idling, macOS will normally allocate threads with a QoS of 17 (utility) and higher to P cores, and those of 9 (background) and lower to E cores. That isn’t guaranteed, and there are circumstances when all threads are allocated to E cores alone, for example when a laptop’s battery is very low and it goes into energy-saving mode.

CPU History

It’s therefore tempting to assume that when a process runs very slowly, it’s being given a low QoS and is pottering along on the E cores. Although that might be correct, it’s a dangerous assumption to make. In this case, to investigate it further, I’ll take a different compressor that offers control over the QoS used for its working threads, such as my free Cormorant or the wonderful Keka.

When compressing an IPSW file of just over 18 GB, using Apple Archive’s LZFSE method in Cormorant takes 7.4 seconds at the maximum QoS of 33, but 114.7 seconds at the minimum QoS of 9. Performing exactly the same compression using aa from the command line takes about 9 seconds, so is clearly being run at high QoS. But using tar to create a tar.gzip takes forever, even longer than Cormorant running at minimum QoS.

Activity Monitor’s CPU History window is a quick and simple way to see what’s going on here, although you must be cautious when trying to interpret values such as CPU %., because those shown don’t take into account the frequency cores are run at.

This is Cormorant compressing at high QoS on all 10 of the P cores.

And this is the same compression performed at low QoS, so confined to the 4 E cores.

Compressing using aa in Terminal also makes full use of all the P cores available.

Running tar in Terminal does use the P cores, but runs in a single thread that’s shuffled between cores and takes more than 10 times as long as it would if it could be run in 10 threads.

Thus, the reason that tar is so slow isn’t because it’s given a low QoS and run on the E cores, but that it’s single-threaded (and not performant either). If you want better performance, look for a substitute that can make good use of multiple threads running in multiple P cores.

Exceptions

There are plenty of binaries that are run at low QoS, hence on the E cores, including most of those that are run in the background or scheduled using LaunchAgents and LaunchDaemons. Their property lists should specify a QoS name for their Priority key, which is often Background or Maintenance, for them to be run at a QoS of 9 or lower on the E cores alone.

There’s also the possibility that a command tool may run its own threads and assign a low QoS to them, although that should always be documented.

Summary

• By default, command tools run in Terminal aren’t assigned low QoS and run on E cores.
• Tools that run in single threads will invariably be slower than multi-threaded equivalents.
• Use Activity Monitor’s CPU History window to see which core types threads are run on.

By the nineteenth century a great deal was known about how oil paint worked, but the process of polymerisation to produce a robust paint layer wasn’t really understood until well into the twentieth century. As a result, practices that caused structural failure of the paint layer weren’t uncommon, among them the use of pigments like asphalt, and removing drying oil binder in peinture à l’essence. This article looks at the latter, a technique used by Edgar Degas and others.

Tubed oil paints, certain colours in particular, can be oily, and Degas and others experimented with reducing the amount of oil in their paints. Squeezing paint out of the tube onto blotting paper or rag and removing excess oil shouldn’t cause problems, but peinture à l’essence took that to the extreme, in blotting out as much as possible, then restoring viscosity and flow by adding turpentine, a diluent that’s only going to weaken paint binding.

One of Degas’ earliest paintings of a girl and a woman, once he had started to paint ‘modern life’, is his Beach Scene from about 1869-70. It’s also probably one of his first experiments with peinture à l’essence, as demonstrated in its thin and uneven paint layer in the left foreground, by the white hat.

Seven years later, in his paintings of the Ballet at the Paris Opéra here from 1877, Degas experimented with another method of reducing the binder in his paint layer, by applying pastel over a monotype. He first created this painting on a non-absorbent surface, and while that was still wet used that to make a print on paper, which he completed by applying soft pastel on top.

Degas’ Danseuse dans sa loge (Dancer in her Dressing Room) (c 1879) is one of his experimental paintings combining pastel with peinture à l’essence applied to canvas. The detail view below shows how thinly he applied his paint to the ground, although it’s impossible to judge from that how well it’s adhering.

Oil paint has been so successful and its paint layers so robust because the pigment is sealed in a protective layer of polymerised oil. Pastels adhere far more tenuously, with precious little to bind them to the ground. Removing the drying oil and adding essentially unbound pigment will inevitably result in a fragile if not ephemeral result.

Degas’ Women Combing Their Hair (c 1875-6) is also painted in oils, probably using peinture à l’essence, on paper. The detail below show how its light brown ground shows through the thin and fragile layer of paint.

His remarkable composite work, made using peinture à l’essence, of a Dancer Fastening Her Shoe (c 1893-98), brings together four different views of the same dancer fastening her left shoe. This may have been inspired by Muybridge and Marey’s composite photos of human motion, and may well have reflected his own experiments in photography.

Among the other painters who seem to have used peinture à l’essence are Paul Gauguin, in his Vue de la Plage de Bellangenay (View Of The Beach At Bellangenay) (1889) above, and Toulouse-Lautrec, in his Danseuse assise aux Bas de roses (Dancer sat at the foot of Roses) (1890) shown below, which follows Degas in combining the technique with pastels.

This detail shows again a thin paint layer with the ground clearly visible between the painter’s gestural marks.

Even Édouard Vuillard gave way to temptation to paint The First Class Compartment in about 1898-1900 using peinture à l’essence, here on a cardboard ground that has been mounted on a panel support.

Fortunately this fad seems to have passed by the early twentieth century.

It’s now almost a year since macOS Sequoia changed security updates, and I’m still being asked how these work. I also suspect a few are wondering whether there will be any changes coming in Tahoe. This article summarises how these work at the moment, and are expected to continue.

Three XProtects

All reasonably recent versions of macOS have three different security features known as XProtect:

• The oldest XProtect scans code just before it’s run. This uses one or two XProtect.bundle items containing Yara rules that determine the known malware it can detect. Currently, those are updated once a week.
• The newer XProtect.app in /Library/Apple/System/Library/CoreServices is only used in Catalina and later. This runs daily scans to look for malware using its scanning modules, and is also known as XProtect Remediator as it removes malware. Currently, this is updated once a month.
• The newest and hidden Behavioural XProtect watches constantly for suspicious behaviour such as apps accessing folders used by Safari and other browsers, according to its Bastion rules. Those rules are contained inside XProtect.app and are updated with it.

So for the time being, you should expect your Mac to update XProtect’s bundle every week or so, and the XProtect app (XProtect Remediator, and Bastion rules) every month.

XProtect Remediator

Roughly once a month, your Mac should download and install a file named something like XProtectPayloads_10_15-155, where the last three digits are its new version number. This is delivered and installed automatically through Software Update, if you have it set to Install Security Responses and system files. You can also download and install it manually using the softwareupdate command, or, easiest of all, using my free SilentKnight.

Legacy XProtect

All fairly recent versions of macOS have a copy of XProtect.bundle in /Library/Apple/System/Library/CoreServices. This is also downloaded and installed using Software Update, softwareupdate or SilentKnight, and the file name is something like XProtectPlistConfigData_10_15-5314. In versions of macOS before Sequoia, this is the only copy of that bundle, and once that has been installed, XProtect is up to date.

iCloud XProtect

Almost a year ago, Apple changed XProtect in Sequoia, and since then Tahoe has followed suit. They not only have legacy XProtect with its XProtect.bundle in /Library/Apple/System/Library/CoreServices, but they have a separate copy of the same bundle in /private/var/protected/xprotect. If you compare those carefully, you’ll see differences, as the legacy copy is signed, but the other isn’t.

When XProtect is updated, Sequoia and Tahoe therefore download and install those two copies separately. The legacy copy is updated exactly the same as in older macOS, through Software Update, softwareupdate or SilentKnight.

The new copy of XProtect.bundle in /private/var/protected/xprotect can’t be updated by softwareupdate or SilentKnight, though. Updating the legacy copy doesn’t alter or update that, which is instead performed over a connection to iCloud. To check and update that copy, you can use the xprotect command in Terminal. The command
xprotect version
returns the version of XProtect installed in the new (iCloud-based) location, which can be different from the legacy copy. You can check whether an iCloud update is available using the Terminal command
sudo xprotect check
and entering your admin password when prompted to do so. If that version number is higher than that currently installed in the new location, then the command
sudo xprotect update
will download and install XProtect from iCloud into its new location.

Can the two XProtects interact?

In Sequoia and Tahoe, both versions of XProtect.bundle will eventually be downloaded and installed automatically. Sometimes, when you’re installing one, the other is also updated. That doesn’t occur because one updater can also update the other copy, but simply because the automatic update process has run. In the early days of Sequoia, the xprotect update command could update the iCloud version from the legacy version, but that stopped working many months ago.

Another behaviour that can appear confusing is when legacy XProtect updates but the iCloud version doesn’t. That often occurs soon after a new version is released, as it almost invariably is made available via Software Update first, so resulting in the legacy version being updated quickly. Sometimes the iCloud update isn’t made available for several hours later, and that may give the impression that updating the legacy version is somehow blocking the iCloud update. That’s easy to check using the xprotect check command: until that reports the new version is available, the xprotect update command won’t work.

How do I know when these updates are available?

I am sometimes asked where I look to check when XProtect and other updates are available, as if Apple publishes this information somewhere. It doesn’t. I use the same tools that you can use, SilentKnight to check for updates via softwareupdate, and the xprotect command tool for those delivered from iCloud. As soon as I find a new update, I install it here, update the databases on Github used by SilentKnight and Skint, analyse the contents of the update, post the announcement here, post that on X/Twitter, then update this blog’s System Updates page.

Do different Macs update differently?

All the code for these updates is contained in the copy of macOS installed in the SSV, the signed snapshot of the System volume that runs your Mac. For any given version of macOS, all Macs, both Intel and Apple silicon, have identical SSVs, although there are differences in their cryptexes and Data volumes. Thus, XProtect updates work exactly the same on all Macs running Sequoia 15.6.1 from my ancient iMac Pro to my latest Mac mini M4 Pro, and I check those with every update as well.

I hope you find these helpful.

Dante and Virgil are ferried across the River Styx to land at the entrance to the city of Dis, the lower depths of Hell (circles 6-9), but its gate is slammed shut on Virgil when he tries to secure their admission. He reassures Dante that he has been here once before, but Dante is staring at the top of the gate where the three Furies have appeared, wreathed in snakes.

Virgil names them to Dante: Megaera on the left, Alecto to the right, and Tisiphone between them. Megaera represents evil deeds, Tisiphone evil words, and Alecto evil thought. They are another crossover drawn from classical mythology into Dante’s Christian Hell.

The Furies call on Medusa to turn Dante to stone with the sight of her face, and Virgil makes Dante turn to look away from them, and close his eyes tightly.

A strong wind then blows across the marsh of the Styx towards them, as a mass of ghosts there part to make way for an angel who walks across the water towards the walls of Dis. Virgil gets Dante to bow in deference to the angel as he passes them by and opens the gate of Dis for them with his rod. The angel chides those inside for their resistance and immediately returns the way he came.

Virgil then leads Dante through the open gate onto a plain, its ground made uneven by the many tombs set in its surface. The stones on top of them are open, revealing flames within, and letting out cries of pain. Virgil explains that these contain heretics and their followers, and that their lids will only be closed with the Final Judgement. By heresy, Dante here means that these sinners denied the immortality of the soul.

Virgil points out the tomb of the Epicureans, then Dante is startled by the appearance of the head and upper body of Farinata degli Uberto in another.

Farinata was the leader of the Ghibellines of Florence, a family grouping that had been fighting against the Guelphs, including Dante himself. The Florentine then asks Dante who his ancestors were, and reveals that he had opposed Dante’s family. With Farinata are the last Holy Roman Emperor Frederick II and Cardinal Octavian, Ottaviano degli Ubaldini, who had been a powerful supporter of the Ghibellines prior to his death in 1273.

With Dante thinking on what he had heard, Virgil leads him into a gorge, in which they descend deeper into Hell.

The artists

William Blake (1757–1827) was a British visionary painter and illustrator whose last and incomplete work was an illustrated edition of the Divine Comedy for the painter John Linnell. Most of his works shown in this series were created for that, although he did draw and paint scenes during his earlier career. I have a major series on his work here.

Gustave Doré (1832–1883) was the leading French illustrator of the nineteenth century, whose paintings are still relatively unknown. Early in his career, he produced a complete set of seventy illustrations for translations of the Inferno, first published in 1857 and still remain in use. These were followed in 1867 by more illustrations for Purgatorio and Paradiso. This article looks at his paintings.

John Flaxman (1755–1826) was a British sculptor and draughtsman who occasionally painted too. When he was in Rome between 1787-91, he produced drawings for book illustrations, including a set of 111 for an edition of The Divine Comedy. In 1810, he was appointed the Professor of Sculpture to the Royal Academy in London, and in 1817 made drawings to illustrate Hesiod, which were engraved by William Blake.

Joseph Anton Koch (1768-1839) was an Austrian landscape painter, who worked mainly in Neoclassical style. During his second stay in Rome, he was commissioned to paint frescos in the Villa Massimi on the walls of the Dante Room there, which remain one of the most florid visual accounts of Dante’s Inferno. He completed those between 1824-29.

Bernardino Poccetti (1548-1612) was an Italian Mannerist painter and print-maker who was born in Florence and painted some magnificent frescoes in the palaces of the richest families there.

John Singer Sargent (1856–1925) was an American painter who worked much of his career in Europe. Trained in Paris, he was a highly successful portraitist in Paris then London. One of the most gifted and prolific painters of the nineteenth century, his work is rich in bravura brushstrokes and highly individualistic. In his later career, he painted large murals on the East Coast of America, including Orestes Pursued by the Furies in Boston, MA, which he started in 1922, and completed in 1925, just prior to his death. Over its 100 square feet of canvas, it shows a young and naked Orestes cowering under the attacks of the Furies, as he tries to run from them.

References

Wikipedia
Danteworlds

Robin Kirkpatrick (trans) (2012) Dante, The Divine Comedy, Inferno, Purgatorio, Paradiso, Penguin Classics. ISBN 978 0 141 19749 4.
Richard Lansing (ed) (2000) The Dante Encyclopedia, Routledge. ISBN 978 0 415 87611 7.
Guy P Raffa (2009) The Complete Danteworlds, A Reader’s Guide to the Divine Comedy, Chicago UP. ISBN 978 0 2267 0270 4.
Prue Shaw (2014) Reading Dante, From Here to Eternity, Liveright. ISBN 978 1 63149 006 4.

I hope that you enjoyed Saturday’s Mac Riddles, episode 324. Here are my solutions to them.

1: Last edit from KeyGrip but not for the amateur.

2: Movement to accompany 1 for its titles and effects.

3: Opening that closed for your photos a decade ago.

The common factor

I look forward to your putting alternative cases.

Whether you make use of it or not, each APFS or HFS+ volume contains data to support macOS versioning, a feature in many Mac apps now, including most of Apple’s own, such as Preview, TextEdit, Pages and Numbers. Unless you block the database from being created, every time you save a document in an app that offers a Revert To command in its File menu, the current version will be saved to that database. There is no way to disable this feature in individual apps. In some cases, that database can cause problems.

Each volume used to store normal working files has at least three hidden folders at its root level:

• .fseventsd with file system events for that volume recorded in a series of files,
• .Spotlight-V100 containing the volume Spotlight indexes, detailed here,
• .DocumentRevisions-V100 containing the volume’s version database.

The last of those is locked away securely to prevent user access. As far as I’m aware, unlike the other two, it hasn’t been described in detail recently, and doesn’t appear in the otherwise comprehensive accounts of macOS by Amit Singh or Jonathan Levin. This article tries to rectify that.

Structure and function

The .DocumentRevisions-V100 folder contains:

• .cs, containing ChunkStorage, with the ChunkStoreDatabase, and deeply nested folders of numbered storage chunks
• AllUIDs, containing a nested com.apple.documentVersion folder with each version stored in a dataless file named by its UUID
• db-V1, containing db.sqlite, the database of versions
• LibraryStatus, a property list indicating whether the database state is trustable
• metadata, a property list containing DISK_UUID and tookThinningOver values
• purgatory, most commonly an empty folder
• staging, also commonly empty.

When an app that supports versioning saves a file, the current version is added as a dataless file to a folder in AllUIDs, with its UUID as its name, its data are added to the ChunkStoreDatabase, and its details are added to the database in db-V1. Chunk sizes typically range up to just over 20 MB. The service responsible for versioning is revisiond, and the subsystems you’ll encounter in the log are com.apple.foundation.filecoordination and com.apple.chunkinglibrary.

Retrieving a version thus consists of looking it up in the db.sqlite database, and reconstituting that version as a file, using the dataless file with its attributes and metadata in the file UUID, and its data restored from the ChunkStore.

Apps other than the original used to create those versions can also access all the saved versions of any file, but to do so they must be able to open the current version, so having appropriate privileges and privacy settings. This effectively protects access to the contents of the versions database according to the restrictions imposed on its current version.

Backing up

For many years, until macOS Catalina, Time Machine dutifully backed up .DocumentRevisions-V100 folders, although it has never been able to restore them successfully. This is because of its dependence on reuniting chunks of data with a dataless file, and apparent reliance on inode numbers. Copying a .DocumentRevisions-V100 folder to another volume produces a weird result, as the dataless files in the com.apple.documentVersion folder may then point to completely different files.

Third-party backup utilities like Carbon Copy Cloner also don’t back up the folder, as they too are unable to restore it successfully. As a consequence, restoring from a backup, or migration from another volume or Mac, always loses all saved versions.

Housekeeping

The most common cause of problems with the version database is excessive size. Although its size isn’t readily discoverable, it can be a major contributor to that attributed to System Data in Storage settings and third-party utilities, and in some cases can exceed 100 GB.

In the past I had suspected versioning of using hard links or, in APFS, clone files, to achieve economic use of storage, but that appears to be the role of the ChunkStore. Multiple versions of some file types such as JPEG images appear to require a similar amount of storage as would individual files, but others such as RTF can appear significantly more efficient.

ChunkStore size is also dependent on its housekeeping. When a single large JPEG image with 12 versions was deleted, the size taken by chunks didn’t change until the Mac was shut down and started up again. ChunkStore housekeeping routines are clearly performed following start up, but may also occur at periodic intervals later.

Thus the best way to reduce the size of the ChunkStore is:

• Identify documents whose saved versions are likely to be taking a lot of space in the version database.
• For each of those documents, to remove unwanted versions.
• Restart the Mac and leave it to perform ChunkStore housekeeping.

How to identify documents with many versions

My free utility Revisionist has a version crawler that will list all files in a volume or folder with the number of versions they currently have stored in that volume’s .DocumentRevisions-V100 folder. This is accessed in its Open Crawler command in the Window menu. That doesn’t attempt to estimate their size, though.

It’s not uncommon to discover some files with more than 100 versions. On one of my Macs, the current record is 230 versions, and it has several with over 100. Some apps such as Pages often generate large files, where even 20 saved versions can use substantial storage.

How to remove versions

To remove all versions of a document quickly and simply:

• Select the document in the Finder and Duplicate it using Command-D.
• Delete the original file and rename the duplicate.

This is because versions aren’t retained by clone files.

To remove some versions of a document, open that document in Revisionist, select the version(s) you want to delete, then click the Delete button. Note that, because of the way the version database works, there is no undo. Deleted versions cannot be recovered, and because they’re not backed up, you can’t restore that document and recover the versions from there.

In yesterday’s article, I looked at how William Blake’s late painted etching of The Ancient of Days isn’t what it seems, and tells a story unique to Blake’s personal mythology. This article looks an earlier work that until relatively recently was misidentified as a painting of Hecate.

According to Blake’s mythology, Enitharmon is partner, twin, and inspiration to Los, and mother of Orc. She is spiritual beauty, and her image here was most probably modelled on the artist’s wife Catherine. In The Night of Enitharmon’s Joy (c 1795), she establishes her Woman’s World, with a false religion of chastity and vengeance, which is Blake’s view of the 1800 year history of the ‘official’ Christian church.

As the moon to the sun of Los, she is accompanied by symbols of night, such as the owl and bat. She also plays the role of Eve, which may explain the head of a snake peering out towards her. The donkey eating thistles underlines Blake’s rejection of the ‘official’ church, and the two figures behind Enitharmon face in and bow their heads in guilt. The book on which Enitharmon’s left hand rests is Urizen’s ‘Book of brass’, in which his repressive laws are laid down.

If you didn’t know Blake’s mythology, identifying her as Hecate seems reasonable.

Stéphane Mallarmé’s drawing of a classical sculpture of Hecate, Greek Goddess of the Crossroads was engraved for his illustrated account of classical mythology published in 1880. This is her most conventional representation: fully triple-bodied, holding a key at the left, and torches to the left and right, with a symbol of the moon on her forehead.

Hecate has also been depicted more like Eve with a serpent, as seen in Francesco de’ Rossi’s fresco of her from 1543-45. He hints at her triple body with the heads on which she is standing, and she wears a coronet of the moon, her association with night, hence with the owl in Blake’s painting.

William-Adolphe Bouguereau flies his owls in support of a personification of the mythical Night (1883), as do others painting similar motifs. But the owl is also famously associated with Minerva.

Hendrik Goltzius shows a classical and fairly complete set of her attributes in his Minerva (as the Personification of Wisdom) from 1611: the owl, her distinctive helmet, here decorated with olive leaves, a spear, books, and great beauty.

Blake’s mythology has an elaborate and sometimes opaque genealogy. Los and his emanation Enitharmon have children, the first of whom is Orc. As Los is spiritual revolution, so Orc is revolution in the material world. Orc hates his father Los in an Oedipus complex of love for his mother Enitharmon. As shown in Los and Orc (c 1792–3) above, Los is driven to bind Orc to a rock on the top of Mount Atlas, using the chain of jealousy. Orc’s limbs then become rooted in the rock, pinning him there. This cannot prevent Orc’s imagination from raging, though, and permeating everything.

One of the fundamental concepts in Blake’s mythology is that of pairings: there are many elements with both male and female counterparts, the latter being termed emanations. These might take the generation of Eve from Adam as their prototype. Nowhere does Blake envisage a pantheon of gods, but stretches the Jewish and Christian concepts of a single God, going far beyond the Christian Trinity. These include expressions of God associated with particular eras, such as the vengeful God of the Old Testament, and those of particular interpretations that Blake deprecates.

William Blake wasn’t the only artist in Britain at the time who painted new stories. Henry Fuseli did too.

Fuseli’s painting of Percival Delivering Belisane from the Enchantment of Urma (1783) shows a narrative that the artist had invented for this painting. It appears to be one of a series, although only one other work has been identified as part of that, and that is only known from a print of 1782. He also preceded this series with a single painting of Ezzelin and Meduna (1779), referring to another unique narrative, which doesn’t appear to have any associated works.

Fuseli provides the viewer with a rich array of ‘Gothic’ narrative elements to form their own account of the story. There are visions of faces in the distance on the left, chains leading to an unseen figure apparently manacled into a bed at the right, Percival swinging a sword above his head, to strike the cloaked figure of Urma in the left foreground, and a beautiful young woman, presumably Belisane, embraced by Percival’s left arm, kneeling on the floor.

References

Blunt, A (1959) The Art of William Blake, Oxford UP.
Butlin, M (1981) The Paintings and Drawings of William Blake, 2 vols, Yale UP. ISBN 978 0 300 02550 7.
Damon, S Foster (2013) A Blake Dictionary, the Ideas and Symbols of William Blake, updated edn., Dartmouth College Press. ISBN 978 1 61168 443 8.
Vaughan, William (1999) William Blake, British Artists, Tate Publishing. ISBN 978 1 84976 190 1.

If you’ve read any of my articles here about the inner workings of CPU cores in Apple silicon chips, you’ll know I’m no stranger to using the command tool powermetrics to discover what they’re up to. Last week I attempted something more adventurous when trying to estimate how much power and energy are used in a single Visual Look Up (VLU).

My previous tests have been far simpler: start powermetrics collecting sample periods using Terminal, then run a set number of core-intensive threads in my app AsmAttic, knowing those would complete before that sampling stopped. Analysing dozens of sets of measurements of core active residency, frequency and power use is pedestrian, but there’s no doubt as to when the tests were running, nor which cores they were using.

VLU was more intricate, in that once powermetrics had started sampling, I had to double-click an image to open it in Preview, wait until its Info tool showed stars to indicate that stage was complete, open the Info window, spot the buttons that appeared on recognised objects, select one and click on it to open the Look Up window. All steps had to be completed within the 10 seconds of sampling collections, leaving me with the task of matching nearly 11,000 log entries for that interval against sampling periods in powermetrics' hundred samples.

The first problem is syncing time between the log, which gives each entry down to the microsecond, and the sampling periods. Although the latter are supposed to be 100 ms duration, in practice powermetrics is slightly slower, and most ranged between about 116 and 129 ms. As the start time of each period is only given to the nearest second, it’s impossible to know exactly when each sample was obtained.

Correlating log entries with events apparent in the time-course of power use is also tricky. Some are obvious, and the start of sampling was perhaps the easiest giveaway as powermetrics has to be run using sudo to obtain elevated privileges, which leaves unmistakeable evidence in the log. Clicks made on Preview’s tools are readily missed, though, even when you have a good estimate of the time they occurred.

Thus, the sequence of events is known with confidence, and it’s not hard to establish when VLU was occurring. As a result, estimating overall power and energy use for the whole VLU also has good confidence, although establishing finer detail is more challenging.

The final caution applies to all power measurements made using powermetrics, that those are approximate and uncalibrated. What may be reported as 40 mW could be more like 10 or 100 mW.

In the midst of this abundance of caution, one fact stands clear: VLU hardly stresses any part of an Apple silicon chip. Power used during the peak of CPU core, GPU and neural engine (ANE) activity was a small fraction of the values measured during my previous core-intensive testing. At no time did the ten P cores in my M4 Pro come close to the power used when running more than one thread of intensive floating-point arithmetic, and the GPU and ANE spent much of time twiddling their thumbs.

Yet when Apple released VLU in macOS Monterey, it hadn’t been expecting to be able to implement it at all in Intel chips because of its computational demand. What still looks like magic can now be accomplished with ease even in a base M1 model. And when we care to leave our Macs running, mediaanalysisd will plod steadily through recently saved images performing object recognition and classification to add them to Spotlight’s indexes, enabling us to search images by labels describing their contents. Further digging in Apple’s documentation reveals that VLU and indexing of discovered object types is currently limited by language to English, French, German, Italian, Spanish and Japanese.

Some time in the next week or three, when Apple releases macOS Tahoe, we’ll start seeing Apple silicon Macs stretch their wings with the first apps to use its Foundation Models. These are based on the same Large Language Models (LLMs) already used in Writing Tools, and run entirely on-device, unlike ChatGPT. This has unfortunately been eclipsed by Tahoe’s controversial redesign, but as more developers get to grips with these new AI capabilities, you should start to see increasingly novel features appearing.

What developers will do with them is currently less certain. These LLMs are capable of working with text including dialogue, thus are likely to appear early in games, and should provide specialist variants of more generic Writing Tools. They can also return numbers rather than text, and suggest and execute commands and actions that could be used in predictive automation. Unlike previous support for AI techniques such as neural networks, Foundation Models present a simple, high-level interface that can require just a few lines of code.

If you’ve got an Apple silicon Mac, there’s a lot of potential coming in Tahoe, once you’ve jiggled its settings to accommodate its new style.

One of the golden rules in narrative painting is to tell stories that the viewer is already familiar with, because of the limitations imposed by still images. By the middle of the nineteenth century, though, artists were breaking that rule in what became a new sub-genre of the ‘problem picture’, with open-ended narrative encouraging the viewer to construct their own stories. William Blake was a precursor to that in some of his paintings, and this weekend I look at two examples that try to tell stories we’re unfamiliar with.

At first sight, Blake’s painted etching The Ancient of Days from about 1821 might represent the Christian God seen as master craftsman, forming the world out of the darkness below heaven. That would be an innovative but hardly revolutionary interpretation of the opening of the book of Genesis.

That wasn’t Blake’s intention, though. This represents Urizen, one of many figures from his own mythology, and documented only in the artist’s writings. There, Urizen symbolises reason, his name most probably a semi-conscious pun on your reason. This painting shows Urizen the architect, creating the world using his compasses. He goes on to have the role of the jealous and vengeful god of the Old Testament, but his desire for dominion brings about his downfall into a state of Satan.

Representations of God as architect aren’t common, but Blake’s would be by no means unique.

This frontispiece to a Bible Moralisée from around 1220-30 shows the Christian God as architect, using his compasses during the creation of the world. The compasses continue in various modern symbols, including those that feature in freemasonry, and in its references to the Supreme Being as the Great Architect of the Universe.

Urizen typically appears with long and streaming white hair and beard, as in Blake’s plates throughout his First Book of Urizen from 1796.

But Urizen isn’t the only figure from Blake’s mythology who has long white hair and beard: above is Elohim Creating Adam from 1795, for example.

In Blake’s God Judging Adam also from about 1795, both figures sport long, flowing white hair and beards, which appear to be markers not so much of their ages or identities, but of the ancient nature of events.

Long white hair and beards are of course a long-established tradition in visual art: here is a contemporary example of Tiresias, the blind prophet of Apollo at Thebes, in Henry Fuseli’s Tiresias Appears to Ulysses During the Sacrifice (1780-85). Fuseli was Professor of Painting at the Royal Academy, and a great influence on Blake.

Characteristic of the figure of Urizen in The Ancient of Days is the unusual way in which the figure’s hair and beard stream as if in a strong wind, the figure’s nakedness, and its posture.

This can be traced most immediately to a major work by another contemporary painter who was highly influential on Blake: James Barry’s King Lear Weeping over the Dead Body of Cordelia (1786–8). Barry was also Professor of Painting at the Royal Academy, and the similarities between King Lear’s white hair and beard here, and those of Blake’s Urizen in The Ancient of Days, are striking.

Blunt found another potential source in Pellegrino Tibaldi’s figure of Neptune (1549-51) in his fresco showing the story of Ulysses in the Palazzo Poggi. Although now relatively obscure, Blake saw fresco as being ‘true’ art, and was long an enthusiast of frescos, even if he saw few. A contemporary popular book of prints of frescos included an engraving of Tibaldi’s Neptune, so this image would have been accessible to both Blake and Barry.

It’s likely that Tibaldi’s Neptune was itself a reference to Michelangelo’s earlier frescos in the Sistine Chapel: the detail above showing God creating the sun and moon, and even more important that below showing the creation of Adam (c 1511).

Blake knew both of these sections of the Sistine Chapel frescos well, having engraved them previously. They also link to Blake’s own Elohim Creating Adam above.

Blake’s Urizen the architect, seen creating the world using his compasses, is distinct from both God and Elohim in his nakedness. In Blake’s written narrative, the distinction between Urizen and Elohim becomes more blurred, when the former goes on to have the role of the jealous and vengeful god of the Old Testament, until his desire for dominion brings about his downfall.

It may be tempting to assume that, just because Blake’s paintings appear so original and different, they originate entirely from his own mind. However, Blake was just as likely to borrow from and refer to other visual art as any other master.

References

Blunt, A (1959) The Art of William Blake, Oxford UP.
Butlin, M (1981) The Paintings and Drawings of William Blake, 2 vols, Yale UP. ISBN 978 0 300 02550 7.
Damon, S Foster (2013) A Blake Dictionary, the Ideas and Symbols of William Blake, updated edn., Dartmouth College Press. ISBN 978 1 61168 443 8.
Vaughan, William (1999) William Blake, British Artists, Tate Publishing. ISBN 978 1 84976 190 1.

Here are this weekend’s Mac riddles to entertain you through family time, shopping and recreation.

1: Last edit from KeyGrip but not for the amateur.

2: Movement to accompany 1 for its titles and effects.

3: Opening that closed for your photos a decade ago.

To help you cross-check your solutions, or confuse you further, there’s a common factor between them.

I’ll post my solutions first thing on Monday morning.

Please don’t post your solutions as comments here: it spoils it for others.

Few other companies have had as much influence on the Mac and its success as Adobe. Founded just over a year before Apple launched the Mac, its original mission was to develop and market its new PostScript page description language, originally designed and written by Adobe’s co-founders, John Warnock (1940-2023) and Charles Geschke (1939-2021). Steve Jobs (1955-2011) was an early enthusiast who shared their vision. After an unsuccessful bid to buy Adobe, Apple bought a 19% stake in it and paid in advance for a five-year licence for PostScript. When Apple introduced its first PostScript laser printer, the LaserWriter, in March 1985 the partnership launched the Desktop Publishing (DTP) revolution.

Adobe Illustrator (1987)

The same year the LaserWriter brought PostScript and its fonts to the first DTP designers, Adobe started development of its first retail software product, Illustrator, released two years later in 1987. This is a vector graphics editor aimed initially at creating in Encapsulated PostScript Format (EPSF), so had to render the bézier curves of PostScript into the Mac’s QuickDraw graphics.

Illustrator wasn’t offered for Windows for another two years, and even then was widely criticised for lagging behind its Mac version. It wasn’t until 1997 that the Windows version achieved parity. Adobe’s major competitor, Aldus FreeHand, was preferred by many professionals until Adobe bought Macromedia in 2005, following which it was quietly suffocated.

This is Adobe Illustrator running in Mac OS X 10.2 Jaguar in early 2003.

Adobe Photoshop (1990)

In 1988, Adobe bought the distribution licence to a raster graphics editor already named Photoshop by its original developers, brothers Thomas and John Knoll. The first Adobe version was released for Macs only in February 1990. It has the distinction of being the major app developed using Apple’s MacApp class library, and wasn’t released for Windows until late 1992, by which time it was establishing itself as the standard, particularly for pro photographers. In 2007 it was joined by Adobe Photoshop Lightroom, an image management app that became the standard when Apple discontinued Aperture in 2015.

This is Adobe Photoshop in Mac OS 9.2, in late 2002.

And this is its matching Mac OS X version in 10.2 Jaguar.

Adobe Premiere (1991)

Digital non-linear video editing was in its infancy in 1991, when SuperMac Technology developed a QuickTime-based app to support its Video Spigot capture card. Adobe purchased the whole project, and four months later at the end of 1991 released the first version of Adobe Premiere. Although severely constrained by hardware of the time, it proved another successful Mac-only product until its Windows version was released almost two years later, and the product was renamed Adobe Premiere Pro in 2003.

In 1995, Premiere was joined by After Effects following Adobe’s acquisition of Aldus the previous year. After Effects provides digital effects including motion graphics and compositing. In 1999, Apple released Final Cut Pro, whose early development had been by the first Premiere development team working for Macromedia, and has since added Motion and other apps to form its Pro suite. They successfully competed against Adobe’s video products on the Mac.

PDF and Adobe Acrobat (1993)

I have already given a fuller account of the history of PDF and Adobe Acrobat on Macs.

This is Acrobat Distiller 4.0 running on Mac OS 9.1 in early 2001, showing some of its bewildering array of options for turning PostScript files into PDF.

Adobe provided its free Acrobat Reader for Mac OS X, here seen in 10.0 Cheetah.

Adobe FrameMaker (1995)

FrameMaker, originally developed by Frame Technology, is a high-end technical publishing system bought by Adobe in 1995. It was then offered in a premium version with extensive support for SGML, seen here in 2002, two years before Adobe dropped this Mac version.

Adobe PageMaker (1995-2001)

From its launch in 1985, the leading page layout app for Macs had been Aldus PageMaker, which Adobe acquired when it purchased Aldus in 1994. By this time, PageMaker was under increasing pressure from QuarkXPress, which had become preferred by many professionals. As a result, Aldus had already started to develop what it claimed would be its “Quark killer”, and Adobe continued that. It then discontinued support for PageMaker in a final version released in 2001, which notoriously didn’t support Mac OS X and was never ported to Intel Macs either.

Adobe InDesign (1999)

Early development on what was to become Adobe InDesign had started in Aldus before it was swallowed up by Adobe, and its first version was released in 1999, for both Windows and Mac OS. When Mac OS 10.0 Cheetah was released in March 2001, InDesign was its first native page layout app, as well as the first to support Unicode and advanced features of OpenType fonts. As QuarkXPress entered a decline, InDesign became the DTP product of choice.

This is Adobe InDesign in its early days, seen here editing Christmas cards in Mac OS X 10.2 Jaguar in December 2002.

Adobe Dreamweaver (2005)

Dreamweaver is a website development app that originated in Macromedia in 1997, and was acquired by Adobe with its purchase of that company in 2005.

Adobe Dreamweaver is seen here running in Mac OS X 10.6 Snow Leopard in August 2009.

Flash (2005-2020)

Another of Macromedia’s products that Adobe acquired in 2005 was Flash, a rich multimedia software platform that became enormously popular in websites including YouTube and many corporate sites. Flash came with its own scripting language ActionScript, but proved a security nightmare because of its long series of exploited vulnerabilities. Although Flash Player was almost universal on Macs, Apple refused to allow Flash support on its devices, leading to a bitter standoff between Steve Jobs and Adobe. About a year later, much to the relief of security staff around the world, Adobe announced it would cease Flash development; it was deprecated in 2017, and all support stopped at the end of 2020.

‘Shockwave Flash’ and the Flash Player plagued Mac OS X Tiger in 2006.

Others

There have been and still are many other apps from Adobe. One of my favourites was LaserTalk, first released by Emerald City Software in 1988. This was a PostScript debugger acquired by Adobe and bundled in its PostScript SDK. Finally, there was Adobe Streamline, a tool for converting bitmap graphics into Adobe Illustrator vector graphics, first released in 1989, and absorbed into Illustrator in about 2001. No doubt you will also have your own favourites.

Apple sold its 19% stake in Adobe in 1989, and in 2011 Adobe introduced its Creative Cloud subscription service, that two years later replaced its popular Creative Studio DVD distributions with perpetual licences.

Dice have been thrown and rolled by people throughout recorded history. Early dice were often irregular, made of bone or stone and used primarily for gambling. Although they don’t appear to have played any significant role in mythology, their role in the events of the Crucifixion is well recorded in the New Testament Gospels.

Jacopo Tintoretto’s huge and magnificent Crucifixion from 1565 depicts the biblical account of guards gambling with dice, as seen in the detail below.

On the left of this detail, two men are gambling with dice in a small rock shelter suggestive of a tomb. To the right of them, a gravedigger has just started his work with a spade.

The Christian Church has generally taken a dim view of gambling, and shunned dice. Several artists have expressed this in paint, but none so forcefully as Hieronymus Bosch.

For Bosch and his patrons, gambling was definitely one of the cardinal sins. It appears in the garden of Hell in the right panel of his magnificent Garden of Earthly Delights from about 1495-1505. In this damning conclusion, figures are mutilated and tormented in a nightmare landscape dominated by non-human creatures and alarming objects, where gambling takes the foreground.

In the foreground, a huge blue bird, wearing a cauldron on its head and swallowing a whole human, presides over the scene. Two main groups of victims here are clustered around objects associated with gaming and gambling, and those for making music, then associated with the work of the devil, and immoral activities such as dancing. Playing cards are scattered on the ground beneath an overturned gaming table, and dice are balanced precariously on an index finger and on the head of a naked woman. From among that cluster of figures, a pair of dark blue non-human arms holds high a backgammon board with three dice.

Not all cultures have been as damning, though.

Albert Anker turns to classical times to put his spin on gambling games in his Knucklebone Players (1864). Three youths are here playing a game of greater skill, but still frequently the basis of gambling. The distinguished men in the background are hardly the sort to frequent a gambling den, surely?

Nevertheless, playing with dice continued as a cardinal sign of sin.

Alcohol, and that other vice tobacco, are cited in David Teniers the Younger’s The Dice Shooters (1630-50). In common with other paintings of card-playing and gambling in this period, it’s set in a dingy room in a rough tavern. Drawing on their clay pipes and with glasses of beer in hand, a group of men are completely absorbed in gambling large stacks of coins on the throw of their dice.

William Hogarth’s successor Thomas Rowlandson painted his Gaming Table in watercolour in 1801. Players here are putting their stakes on dice, which are about to be revealed by the man at the far right of the table, who seems to have been raking the money in.

Although Gustave Courbet’s portrait of the operatic singer Louis Gueymard (1822–1880) as Robert le Diable (1857) shows the last scene in Act 1 of Giacomo Meyerbeer’s opera Robert le Diable (1831), its message is clear. In this scene, Gueymard’s character Robert gambles away his entire estate on dice; in the opera this is marked by the aria L’or est une chimère: ‘gold is but an illusion’.

Dante Gabriel Rossetti is less convinced. In his watercolour of Hesterna Rosa from 1865, he shows a moment from the contemporary play Philip van Artevelde, written by Henry Taylor in 1834. Van Artevelde was a Flemish patriot who lived between about 1340-1382, and led the Ghent rebellion in 1381, only to be crushed to death in battle the following year. In Taylor’s play, van Artevelde has a relationship with a woman of lower class; in this scene, his lover has paused to reflect on her life while he plays dice with a friend. The painting’s title means yesterday’s rose, and draws on the theme of the fallen woman, so popular with Rossetti.

Murillo’s Young Boys Playing Dice of about 1675 adopts a different theme, of gambling among the poor and vulnerable. Two scruffy urchins from the streets of Seville are throwing dice for the small piles of change which are probably their entire fortunes. A third stands over them, chewing at a bread roll while his dog looks up longingly at the food.

Create a new folder inside your Documents folder, and inspect its permissions in the Finder’s Get Info dialog. You should see that you, as the owner of that folder, have Read & Write privileges, your group staff can only read it, as can everyone. Have you ever wondered how that new folder, or any new file, gets its permissions set in that way? This article explains how, and how you can control that.

Although it might appear to be of little use, there are circumstances when it becomes really important, for example when you create folders and files in shared locations. What if you were to use a sharepoint on a NAS that you shared with several others, and created folders and files there, with those same permissions? Although your colleagues would be able to read that folder and documents, they wouldn’t be able to write to them. Instead, you’d want those to give both Read & Write privileges to everyone in your group, and that’s something you can set with your umask.

Your Mac has at least two umasks, stored in /private/var/db/com.apple.xpc.launchd/config. One for all your user processes, including the Finder and apps that you run, the other for system processes, stored in the same place. If you want to override the default umasks, then you do so using the launchctl command in Terminal. Before you can do that, you need to know how to specify those umasks using octal numbers.

Octal permissions

The most compact and convenient way to express permissions isn’t in hexadecimal, but octal, and that’s standard across all Unix-based systems. Open a file or folder in my free utility Precize, for instance, and it reports its Posix permissions as three octal digits, together with the names and ID numbers of the owner and group.

A complete set of permissions actually consists of four octal digits, but the first is used for special bits (setuid, setgid and sticky), which don’t concern us here. The next and most important three digits give the permission settings for the owner, group, and everyone else, in that order.

Each digit is the sum of up to three numbers:

• 4 means that reading is allowed
• 2 means that writing is allowed
• 1 means that a file can be executed, or a directory searched.

So the standard permissions set on that new folder you created work out thus:

• the owner has Read & Write access, and search = 4 + 2 + 1 = 7
• the group has Read only access, and search = 4 + 1 = 5
• everyone has Read only access, and search = 4 + 1 = 5

and the octal permissions of that folder are given as 755. For a shared folder where all in the group need both read and write access, you might want octal permissions of 775 instead.

Octal permissions are used in many places in Unix, hence in command tools like chmod, used to set and change permissions. They’re also used if you want to set your own umask.

Set the umask

Having mastered octal permissions, you now need to understand how a umask is applied to them. It would be far too simple for you to simply specify the umask as the octal permissions, so, as the name suggests, the number you set as a umask is subtracted from the default octal permissions. Default permissions are almost invariably 666 for files, and 777 for folders, the latter to allow for search. Thus the default user umask is 022:

• for a file, default permissions are then 666 – 022 = 644
• for a folder, default permissions are then 777 – 022 = 755, as we saw with the folder above.

To return to my example of someone who is sharing folders with colleagues in their group, and all of them need both read and write access to those shared folders and files, a simple way to accomplish this is for each to change their user umask to 002 from the default of 022. To do that as an admin user, enter the command
sudo launchctl config user umask 002
But before you use that, check there’s a folder at /private/var/db/com.apple.xpc.launchd/config. If there isn’t, that command will result in an error that you can correct by creating that folder.

This applies to all files and folders created by the processes run by a user, no matter where they are created, so extends beyond their shared folders.

Setting a system umask should be exceedingly rare, as that alters the permissions of folders and files created by macOS background services and whole lot more, and could cause utter chaos or security problems. If you really need to, use the same command but with system instead of user in the command line.

Whenever you have changed either the user or system umask, you need to restart your Mac to ensure the new setting is enforced.

Exceptions

Setting a umask doesn’t guarantee that every new folder and file will be created with those permissions, though, as processes with root privileges can set their own umask and are also able to set custom permissions where they wish. If you find a third-party app not respecting the user umask, when there’s no good reason to do different, contact its developer and complain. Good behaviour is essential for apps that work in shared environments.

References

Apple’s detailed support note
man chmod

By 1883, Walter Crane was a successful illustrator who had also established himself as a painter of repute. He was associated with members of the Pre-Raphaelite Movement, including William Morris, although Crane’s paintings remained distinctive and usually strongly narrative.

Like Morris, Crane was a socialist and from 1883 joined a string of related organisations including the Fabian Society, the Social Democratic Federation, and the Socialist League. He also promoted and supported the arts and crafts movement, and played active roles in both the Art Workers Guild and the Arts and Crafts Exhibition Society. For each of these he provided support in the form of illustrations.

Following his earlier Renaissance of Venus (1877), in 1883 he took a contrasting view of La Primavera (Spring), featuring Flora bent picking daffodil flowers on a plain.

Crane’s allegorical narrative of life as a bridge appears unique to him. It shows a newborn baby arriving in the hand of a winged angel in a white punt/gondola, left of centre. The baby is handed over to a mother or nurse, fed at the breast at the bottom left corner, walking up the steps, and learning at the top. Children play, then grow into young adults, and marry as they reach the top of the bridge. Throughout this runs the thread of life.

The mature adult in the middle of the bridge (by its keystone) then ages steadily, bearing the whole globe during the descent. He then gains a long white beard and walking stick during the descent into old age, finally dying, his body being placed in the black punt/gondola, where it is attended by the angel of death. Grieving relatives stand on the shore and make their farewells, one cutting the thread securing the boat to the shore with a pair of traditional scissors.

Crane explained the theme of his Bridge of Life (1884) as “fortune and fame pursued and ever eluding the grasp; til the crown perhaps is gained, but the burden of the intolerable work has to be borne.” It was first shown at the Grosvenor Gallery, then toured venues in the East End of London during a period of social and labour unrest there.

The following year, he painted Pandora in an unusual interpretation that is only loosely connected with the myth of her releasing all the evils of man from a large urn. She is shown draped in grief over a substantial casket, and on its side panel are the figures of the three Fates. At the corners of the casket are guardian winged sphinxes, each clasping a sphere.

Crane’s illustration for Baby’s Own Aesop (1887), engraved by Edmund Evans, underlines many of the differences between his illustrations and narrative paintings. First, the illustration here supports the text on the page, and doesn’t stand alone from it. Look at the picture and you could hardly deduce the accompanying text, but put the two together and you can see how the picture depicts the narrative in the text. Illustrators also have to be careful to ensure that there are no disparities between their work and the text, although narrative paintings often depart from a literal representation.

There are other stylistic clues, such as the use of drawn outlines throughout illustrations, and plain, simple drawings, which are much more likely in illustrations than in standalone paintings, although from the late nineteenth century onwards these appeared increasingly in paintings.

In 1891, Crane visited the US to promote an exhibition of his work there. Unfortunately, he appeared at a meeting of anarchists in Boston and openly expressed his opinion that those found guilty of the Haymarket affair, a bombing at a demonstration in Chicago in 1886, had been wrongfully executed. Despite writing a letter of apology to the press, Crane’s engagements were cancelled and the visit proved disastrous.

From 1887, Crane’s paintings moved away from his socialist politics towards what he described as “the forces of nature in elemental play”. Among the finest of these is Neptune’s Horses.

He painted this oil study for Neptune’s Horses in about 1892. Although it draws its theme from classical mythology, its treatment centres on explaining how that might have originated. It also hints at a visual pun, as the English phrase commonly used to describe breaking waves is white horses.

His finished painting of Neptune’s Horses (1892) reverses that study and brings the god a little closer.

Crane’s book illustration of King Midas with his Daughter, published in 1893, is one of the few works telling this myth directly. It shows the hapless king surrounded by all the gold objects which he has touched, his daughter dead on his knee, cold and gold.

Crane appears to have painted occasional watercolour landscapes, including this view of a pair of tall Lombardy poplar trees on a Bit of the Avon in 1893. There are several rivers of that name in England, and the title may refer to a section known then as the Bit.

The Swan Maidens (1894) is an elaborate fantasy depiction of one of the most widespread folk tales, known in almost every culture recorded around the world. This centres on one or more supernatural females who transform from human to bird form, most generally a swan, or sometimes a goose. This is accomplished by their donning the skin of the bird, as shown here. Swan maidens are featured in William Morris’s epic poem The Earthly Paradise (1868-70), although Crane doesn’t appear to have illustrated an edition.

In the mid-1890s, Crane devoted much time to making woodcuts for an illustrated and decorative edition of Edmund Spenser’s epic The Faerie Queene.

His title page establishes the seriousness of this illustrated edition, completed in six volumes over the period 1895-97, and published in 1897 by George Allen.

Crane’s woodcuts are detailed and delicate, as shown in his opening image of The Patron of True Holinesse in Book 1, Canto 1. These reflect his longstanding involvement with William Morris and his Kelmscott Press, which published 53 books between its creation in 1891 and 1898.

References

Wikipedia

O’Neill M (2010) Walter Crane. The Arts and Crafts, Painting, and Politics, 1875-1890, Yale UP. ISBN 978 0 300 16768 9.

Over the last few weeks, as I’ve been digging deeper into Spotlight local search, what seemed at first to be fairly straightforward has become far more complex. This article draws together some lessons that I have learned.

Apple’s search patents have been abandoned

Having tracked down a batch of Apple’s patents relating to search technologies that are likely to have been used in Spotlight, I was surprised to see those have been abandoned. For example, US Patent 2011/0113052 A1, Query result iteration for multiple queries, filed by John Hörnkvist on 14 January 2011, was abandoned five years later. I therefore have no insights to offer based on Apple’s extant patents.

Search is determined by index structure

Spotlight indexes metadata separately from contents, and both types of index point to files, apparently through their paths and names, rather than their inodes. You can demonstrate this using test file H in SpotTest. Once Spotlight has indexed objects in images discovered by mediaanalysisd, moving that file to a different folder breaks that association immediately, and the same applies to file I whose text is recognised by Live Text.

Extracted text, that recovered using optical character recognition (Live Text), and object labels obtained using image classification (Visual Look Up) are all treated as content rather than metadata. Thus you can search for content, but you can’t obtain a list of objects that have been indexed from images, any more than you can obtain Spotlight’s lexicon of words extracted as text.

Language

Spotlight’s indexes are multilingual, as demonstrated by one of Apple’s earliest patents for search technology. Extracted text can thus contain words in several languages, but isn’t translated. Object labels are likely to be in the primary language set at the time, for example using the German word weide instead of the English cattle, if German was set when mediaanalysisd extracted object types from that image. You can verify this in SpotTest using test file H and custom search terms.

If you change your Mac’s primary language frequently, this could make it very hard to search for objects recognised in images.

Search method makes a difference

The Finder’s Find feature can be effective, but has a limited syntax lacking OR and NOT unless you resort to using Raw Query predicates (available from the first popup menu).* This means it can’t be used to construct a search for text containing the word cattle OR cow. This has a beneficial side-effect, in that each term used should reduce the number of hits, but it’s a significant constraint.

The Finder does support some search types not available in other methods such as mdfind. Of the image-related types, John reports that kMDItemPhotosSceneClassificationLabels can be used in the Finder’s Find and will return files with matching objects that have been identified, but that doesn’t work in mdfind, either in Terminal or when called by an app. Other promising candidates that have proved unsuccessful include:

• kMDItemPhotosSceneClassificationIdentifiers
• kMDItemPhotosSceneClassificationMediaTypes
• kMDItemPhotosSceneClassificationSynonyms
• kMDItemPhotosSceneClassificationTypes.

One huge advantage of mdfind is that it can perform a general search for content using wildcards, in the form
(** == '[searchTerm]*'cdw)

Using NSMetadataQuery from compiled code is probably not worth the effort. Not only does it use predicates of different form from mdfind, but it’s unable to make use of wildcards in the same way that mdfind can, a lesson again demonstrated in SpotTest. mdfind can also be significantly quicker.

For example, you might use the form
mdfind "(kMDItemKeywords == '[searchTerm]*'cdw)"
in Terminal, or from within a compiled app. The equivalent predicate for NSMetadataQuery would read
(kMDItemKeywords CONTAINS[cdw] \"cattle\")

Another caution when using NSMetadataQuery is that apps appear to have their own single NSMetadataQuery instance on their main thread. That can lead to new queries leaking into the results from previous queries.

Key points

• Spotlight indexes metadata separately from contents.
• Text recovered from images, and objects recognised in images, appear to be indexed as contents. As a result you can’t obtain a lexicon of object types.
• Indexed data appear to be associated with the file’s path, and will be lost if a file is moved within the same volume.
• Text contents aren’t translated for indexing, so need to be searched for in their original language.
• Object types obtained from images appear to be indexed using terms from the primary language at the time they are indexed. If the primary language is changed, that will make it harder to search for images by contents.
• The Finder’s Find is constrained in its logic, and doesn’t support OR or NOT, although using Raw Queries can work around that.
• mdfind is most powerful, including wildcard search for content.
• NSMetadataQuery called from code uses a different predicate format and has limitations.

I’m very grateful to Jürgen for drawing my attention to the effects of language, and to John for reporting his discovery of kMDItemPhotosSceneClassificationLabels.

• I’m grateful to Jozef (see his comment below) for reminding me that there is a way to construct OR and NOT operations in the Finder’s Find, although it’s not obvious, and even when you know about it you may well find it difficult to use. I will explain more about this in another article next week.

Apple has just released its weekly update to XProtect for all supported versions of macOS, bringing it to version 5313. As usual, Apple doesn’t release information about what security issues this update might add or change.

This version adds 4 new rules for components of MACOS.MISOMESA and 7 for MACOS.MISOMAGIC, both new codenames in the Yara file, it also adds a new rule for MACOS.SOMA.AUENC, another Soma/Amos component, and amends the existing detection rule for MACOS.DUBROBBER.CHBI.

You can check whether this update has been installed by opening System Information via About This Mac, and selecting the Installations item under Software.

A full listing of security data file versions is given by SilentKnight and SystHist for El Capitan to Tahoe available from their product page. If your Mac hasn’t yet installed this update, you can force it using SilentKnight or at the command line.

If you want to install this as a named update in SilentKnight, its label is XProtectPlistConfigData_10_15-5313

Sequoia and Tahoe systems only

This update has now been released for Sequoia and Tahoe via iCloud. If you want to check it manually, use the Terminal command
sudo xprotect check
then enter your admin password. If that returns version 5313 but your Mac still reports an older version is installed, you may be able to force the update using
sudo xprotect update

Not everyone in the Dutch Republic enjoyed a Golden Age of material wealth. There were some who found worldly goods and pleasures of the flesh were hollow and fleeting, and expressed that in a new sub-genre of Vanitas.

This stems from a long Christian tradition of the worthlessness of earthly possessions, and the promise of life after death. These are crystallised in the wisdom literature of the Bible, in particular a verse from Ecclesiastes, given in the Latin translation of the Vulgate as vanitas vanitatum omnia vanitas, or vanity of vanities, all is vanity, although here the word vanity refers to feelings of emptiness and futility, rather than conceit.

Vanitas paintings thus point to:

• the brevity of life on earth,
• the imminence of death,
• the worthlessness of earthly riches,
• the futility of earthly pursuits and pleasures.

Because those are abstract concepts, the challenge in every Vanitas painting is to find the right symbols, generally accomplished through an allegorical language. They also overlap with other themes in painting such as the Memento mori, the reminder of one’s own mortality.

These have their origins in the Flemish Renaissance, as in Jan Sanders van Hemessen’s Vanitas from about 1535-40. This features an unusual androgynous angel with butterfly wings, cradling a human skull with fragmentary Latin inscriptions. Within the skull is an inset window, through which there is a tiny landscape view. This artist started his career in Antwerp, and is thought to have moved to Haarlem after 1550.

When Vanitas paintings first became popular in the Dutch Republic, they were most commonly expressed in carefully composed still lifes. Clara Peeters’ Fruit, Dead Birds and a Monkey (1615-20) shows a typically strange collection of objects: at first glance a basket of fruit, but the grapes are covered with bloom, a peach is going rotten, and there is a fly on an apple. The little monkey, busy feeding from nuts, is gazing at a small pile of dead birds.

These became elaborate and contrived at times, and sometimes involved a self-portrait.

In Peeters’ Vanitas Portrait of a Woman, the artist gazes into the distance, probably a carefully-angled mirror to see her own reflection. Beside her head is a bubble, a sign of Vanitas. In front of her, on the table, are the contents of a still life, with the worldly symbols of Vanitas: gold and silver coins, jewellery, a couple of dice, with their association with chance and earthly pleasures such as gambling.

In Cornelis de Vos’s Allegory on Transitoriness (1620-29), a mother, possibly the artist’s wife, sits looking full of Vanitas, as her two children blow soap bubbles. Around her, the family’s most valuable possessions are piled up: gold, silver, porcelain, a lute, a string of pearls and other jewellery, and the younger child’s foot rests on a sack of cash. De Vos was Flemish, with his workshop in Antwerp, and often collaborated with Peter Paul Rubens.

Carstian Luyckx, another Flemish painter from Antwerp, brings in additional objects to his undated Allegory of Charles I of England and Henrietta of France in a Vanitas Still Life. These include a globe representing the physical world, the gall from a tree, a snuffed-out candle, seashells, and coral. He uses another common device found in Vanitas painting: an open book, here showing King Charles I, who was executed in 1649, and his wife Henrietta Maria of France, who was deposed as queen of England by the civil wars, forcing her to flee to France in 1644.

David Bailly’s Self-Portrait with Vanitas Symbols (1651) is a complex web of allegory containing multiple portraits referring to the past. The figure shows him as a much younger man, holding the maulstick he used in painting. His true self-portrait at the time is in the painting held with his left hand. Next to that is a painting of his wife, who had already died, and a ghostly image of her is projected onto the wall behind the wine glass.

Gathered in front of the artist are ephemera and other Vanitas objects: the snuffed-out candle, a glass of wine, flowers, and soap bubbles, together with a string of pearls and a skull. If that message isn’t clear enough, he provides the quotation on a piece of paper: vanitas vanitum et omnia vanitas, together with his signature and date. This painting is also unusual for its innovative use of colour and monochrome passages to distinguish its features from their ground. Bailly worked in the city of the Dutch Republic that became most strongly associated with Vanitas painting, Leiden.

Gerard ter Borch’s younger half-sister Gesina modelled for some of his paintings and trained as a painter herself. Between 1667-69, brother and sister painted this Memorial Portrait of Moses ter Borch (1645-1667) to commemorate their younger brother Moses, also a promising artist, who was killed in the Second Anglo-Dutch War in the summer of 1667. Centred on his full-length posthumous portrait, he’s surrounded by Vanitas symbols, including a snake, butterfly, watch, a small pipe, armour, an hourglass, a skull, shells, weapons, snails, fungal decay, and withering flowers. The ter Borchs worked from Amsterdam, although Gerard seems to have travelled more widely.

Evert Collier’s A Vanitas from 1669 is another collection, showing additional objects which became involved in the allegory, including a sword, armour, fine fabrics, and ornamental feathers. Collier was born in North Brabant, trained in Haarlem, then moved to Leiden.

Some later Vanitas paintings developed the theme of young boys blowing bubbles, as in Karel Dujardin’s Boy Blowing Soap Bubbles, an Allegory on the Transitoriness and Brevity of Life from 1663. Dujardin worked in Amsterdam.

There are many more powerful PDF and image editors, yet plenty of us use Preview for those basic little tasks, where we don’t need the complications of a heavyweight. Preview isn’t without its faults, though. It can mutilate PDF annotations made by other apps, and sometimes unexpected things happen. To deal with those it has one feature that’s almost unique among PDF and image editors: it automatically saves versions using the macOS versioning system. This article explains how to make use of that.

Ask to save changes when closing documents

One important control over the behaviour of Preview and many other apps that you may not be aware of is this in the Windows section of Desktop & Dock settings. When combined with apps that use the macOS versioning system its effects are significant.

Ignoring versioning for the moment, when this setting is turned on, if you go to close an open document that has unsaved changes, before it’s closed you’ll be asked whether you want to save that changed document. This is a long-standing safety net that continues to protect us from losing lots of work by accident.

When this setting is turned off, apps may still ask you whether you want to save unsaved changes before closing a document unless the app uses the macOS versioning system. In that case, the app automatically saves a new version without offering any option. This might appear inappropriate, but as that’s non-destructive, it avoids interrupting your workflow: you can always revert to the previous version of that document, provided that you’re aware that it has been saved automatically.

If you’re not aware of what’s going on here, and how the versioning system works, this can cause odd effects you can demonstrate using Preview.

Preview’s saving grace

To see how Preview handles versions and the effect of that setting, find a copy of a suitable PDF or image file and duplicate it in the Finder. Name one copy something like testSavesOff, and the other testSavesOn. Set Ask to save changes when closing documents off to begin with, and open testSavesOff in Preview.

Now perform some destructive editing on that document without saving it, here a radical crop.

Leave it a couple of minutes before closing the document. Following that setting, Preview shouldn’t ask you whether to save the changed document, but will simply close it. Then quit Preview.

Now set Ask to save changes when closing documents on, and repeat the same sequence with testSavesOn instead. When you try to close that document, Preview should now ask you whether you want to save the changed document, to which you should click on Revert Changes to set the document back to its previous state instead.

Inspect the two documents using Quick Look and you’ll see that testSavesOn hasn’t changed, but testSavesOff has, although in neither case did you save those changes yourself.

All in the versions

Although you can see what has happened using Preview’s Revert To menu command, the clearest way to see what has happened to those two documents is to open them using my free Revisionist, which shows their saved versions.

testSavesOn has three saved versions. The current one is the same as the original, but the second version shows the destructive edit that you didn’t save.

testSavesOff has two saved versions, the original, and the current version is that after the destructive edit, which you also didn’t save.

Thanks to Preview’s use of the macOS versioning system, either way you’ve still got access to both versions of that document.

One point to note, though, is that the versioning system doesn’t automatically clean up old versions for you. When you’ve finished editing a document in Preview and don’t want to retain its old versions, delete them either using Revert To in Preview, or with Revisionist. Versions are only retained for the original document as long as it’s stored on the same volume. So you can also wipe old versions by duplicating a document and trashing the original, or copying it to another volume. Once they’re gone, you can’t restore them, as not even Time Machine can back up versions.

The closest an artist comes to painting with pure pigment is when applying soft pastel to the ground. From the earliest cave art, humans have applied powdered earths and chalks to surfaces. Some of the oldest surviving masterpieces made using coloured chalks include those of Leonardo da Vinci, and are sometimes incorrectly referred to as pastels.

An example is this drawing of Isabella d’Este from 1500, described here as using “black and red chalk, yellow pastel chalk on paper”. But there is no such thing as “pastel chalk”, any more than there is “oil watercolour”.

Pastels are much more than just a stick of pigmented chalk or coloured earth, as they’re made by mixing pigment and a bulking powder, with water containing a gum or glue, into a thick dough-like paste. That paste is dried slowly in sticks to become sufficiently firm as to be capable of being sharpened and applied to paper or another ground.

Painting in pastels requires many sticks of different colours; although those can be blended on the paper or ground, pastels don’t mix like oil paints to produce good intermediate colours. You can’t paint properly in pastels with just half a dozen different colours, but need dozens or hundreds to support a broad spectrum. This shows one of my sets of pastels, a Winsor & Newton boxed set of 200.

Careful assessment by Thea Burns has established that the earliest painter in pastels was probably Robert Nanteuil.

Nanteuil’s Portrait of Monseigneur Louis Doni d’Attichy, Bishop of Riez from 1663 is one of the first true pastel paintings, relatively small, but expertly worked. When these became popular in the eighteenth century they quickly became all the rage. Unlike oil paints applied in layers over a period of weeks, pastels adhere to the ground mechanically, and have no drying time. A good pastellist could produce a fine portrait in just a few sittings, making them far less demanding on both parties, much quicker, and of course considerably cheaper. The ‘look’ of pastel paintings also came into vogue, with flesh looking lifelike with a soft, matte finish.

Initially there were no fixatives to help the adhesion of pastel to ground, so they all had to be glazed, and even then didn’t prove as durable as a well-made oil painting. But at that price, only the very rich would care.

Next, mainstream artists started using pastels in preparatory work and sketches, here Charles Antoine Coypel’s dramatic portrait of Medea (c 1715).

One of the most brilliant of this first big wave of pastellists was Rosalba Carriera, whose work demonstrated that a good pastel painter could match the accomplishments of the best oil painters of the day. She had a painterly style at times, as shown in her rich marks in Africa, for which I don’t have a date.

In the fingers of a skilled pastellist, materials like hair and fur that had long challenged painters in oils became great strengths. Carriera’s superb Self-Portrait as ‘Winter’ from 1730-31 is a fine example, as seen in the detail below.

Look carefully and you can see individual grains of pastel that form each mark she made. She didn’t just apply her pastels dry and from the stick, but in places turned them back into a paste using water, and applied that to the paper with a brush.

The star pastellist of the middle of that century was undoubtedly Maurice Quentin de La Tour, whose works are readily seen in the Louvre and elsewhere.

De La Tour not only excelled at modelling softer surfaces and materials to which pastels are so suited, but tackled harder and glittery materials used in jewellery and the like. They’re particularly well shown in his Portrait of Marie-Josèphe of Saxony, Dauphine of France (1731–1767) (1756-60).

After de La Tour, the next brilliant pastellist was quite a contrast: Jean-Etienne Liotard, whose meticulous realism is just breathtaking. Applying his pastels to parchment rather than paper, he was able to paint painstakingly detailed works like The Chocolate Girl (c 1744-45). This shows how the medium was moving on from regular portraits.

Only when you see the patterned grain of the pastel on parchment does it become clear that this is not oil paint. I still marvel at the glass of water: surely a demonstration tour de force to make the viewer gasp in wonder.

Louise Élisabeth Vigée Le Brun’s simple portrait of a baby from about 1790 takes up from where Carriera and de La Tour had made their marks. This infant’s face is softly rendered, but their clothes are sketched in a loose style far in advance of oil paintings of the day.

Pastel painting remained popular through the nineteenth century, but its next major advances came with those around the Impressionists, rather than the core Impressionists, who overwhelmingly preferred oils.

Édouard Manet’s Woman Fastening Her Garter (1878-79) shows a motif many would associate more with Degas, and a spontaneous and sketchy style, with an emphasis on form.

Paul César Helleu was radical and exciting in his pastels; his portrait of Consuelo Vanderbilt, Duchess of Marlborough (c 1900) combines perfect, smooth blending over her face with vigorous mark-making through the fabrics and the ornate frame of the chair, as shown in the detail below.

Edgar Degas was another innovative painter in pastels, whose work encouraged Odilon Redon to take the medium on into the twentieth century.

His recurrent theme of a small sailing boat, which kept appearing in Redon’s later paintings, was expressed most extensively in his pastels. Some, like Flower Clouds (c 1903), above, show the boat sketched in roughly, his paper being dominated by nebulous patches of colour from behind.

His best-known painting of the boat, The Yellow Sail (c 1905), below, was painted in pastel too. He exploits new and more intense pigments here, for the sparkling gems in the boat, and the clothing of the two women.

Although the period since has seen new media such as acrylics, there is still nothing else like painting in pure pigment.

Reference

Thea Burns (2007) The Invention of Pastel Painting, Archetype. ISBN 978 1 904982 12 3.

Look in the log, and Visual Look Up (VLU) on an Apple silicon Mac apparently involves a great deal of work, in both CPU cores and the neural engine (ANE). This article reports a first attempt to estimate power and energy use for a single VLU on an image.

To estimate this, I measured CPU, GPU and ANE power in sampling periods of 100 ms using powermetrics, and correlated events seen there with those recorded in a log extract over the same period, obtained using LogUI. The test was performed on a Mac mini M4 Pro running macOS 15.6.1, using Preview to perform the VLU on a single image showing a small group of cattle in an upland field. Power measurements were collected from a moment immediately before opening the image, and ceased several seconds after VLU was complete.

When used like this, powermetrics imposes remarkably little overhead on the CPU cores, but its sampling periods are neither exact nor identical. This makes it difficult to correlate log entries and their precise timestamps with sampling periods. While powermetrics gives power use in mW, those measurements aren’t calibrated and making assumptions about their accuracy is hazardous. Nevertheless, they remain the best estimates available.

Log narrative

The first step in log analysis was to identify the starting time of powermetrics sampling periods. Although execution of that command left no trace in its entries, as it has to be run with elevated privileges using sudo, its approval was obvious in entries concluding
30.677182 com.apple.opendirectoryd ODRecordVerifyPassword completed
A subsequent entry at 30.688828 seconds was thus chosen as the start time for sampling periods, and all times given below as given in seconds after that time zero.

The following relevant events were identified in the log extract at elapsed times given in seconds:

• 1.3 com.apple.VisionKit Signpost Begin: “VisionKit MAD Parse Request”
• 1.3 com.apple.mediaanalysis Running task VCPMADServiceImageProcessingTask
• 1.4 ANE started and an ObjectDetectionModel run for 0.2 s
• 1.6 ANE activity and a NatureWorldModel run for 0.25 s
• 2.0 ANE activity for 0.15 s
• 2.4 ANE activity for 0.1 s
• 8.1 ANE activity and a UnifiedModel run for 0.01 s
• 8.1 PegasusKit queried Apple’s SMOOT service, the external connection used to populate the VLU window.

Thus, the ANE was run almost continuously from 1.4-2.2 seconds after the start of sampling, otherwise was used little over the total period of about 9 seconds. Over that period of activity, an initial model used to detect objects was succeeded by a later model to identify objects in a ‘nature world’.

Power and energy estimates

From the log record, it was deduced that the VLU was started in powermetrics sample 10 (1.0 seconds elapsed), and essentially complete by sample 75 (7.5 seconds elapsed), a period of approximately 6.5 seconds, following which power use was low until the end of the sampling periods. All subsequent calculations refer to that series of samples and period of time.

Sums, averages and maxima of power measurements for that period of 6.5 seconds are:

• CPU 64,289 mW total, 989 mW average, 7,083 mW maximum (10 P cores)
• GPU 3,151 mW total, 48 mW average, 960 mW maximum (20 cores)
• ANE 1,551 mW total, 24 mW average, 671 mW maximum
• total 68,991 mW total, 1,061 mW average, 7,083 mW maximum.

Thus for the whole VLU, 93% of power was used by the CPU, 4.6% by the GPU, and only 2.2% by the ANE.

For comparison, in the M4 Pro chip running maximal in-core loads, each P core can use 1.3 W running floating point code, and 3 W running NEON code. The chip’s 20-core GPU was previously measured as using a steady maximum power of 20 W, with peaks at 25 W.

As each power sample covers 0.1 seconds, energy used during each sampling period is power/0.1, thus the total energy used over the 6.5 second period of VLU is:

• CPU 6.4 J
• GPU 0.3 J
• ANE 0.2 J
• total 6.9 J.

Those are small compared to the test threads used previously, which cost 3-8 J for each P core used.

Power over time

Power used in each 100 ms sampling period varied considerably over the whole 10 seconds. The chart below shows total power for the CPU.

Highest power was recorded between samples 10-25, corresponding to 1.0-2.5 seconds elapsed since the start of measurements, and most events identified in the log. Later bursts of power use occurred at about 4.2 seconds, and between 6.6-7.1 seconds, which most probably corresponded to opening the info window and performing the selected look-up.

Almost all power use by the neural engine occurred between 1.5-2.1 seconds, correlating well with the period in which substantial models were being run.

Peak GPU power use occurred around 1.0-1.5 seconds when the image was first displayed, at 3.1-3.2 seconds, and between 6.5-7.4 seconds. It’s not known whether any of those were the result of image processing for VLU as GPU-related log entries are unusual.

Composite total power use demonstrates how small and infrequent ANE and GPU use was in comparison to that of the CPU.

Conclusions

Given the limitations of this single set of measurements, I suggest that, on Apple silicon Macs

• power and energy cost of VLU is remarkably low;
• the great majority of work done in VLU is performed in the CPU;
• although use of the neural engine may result in substantial performance improvements, VLU doesn’t make heavy demands on the neural engine in terms of power or energy use;
• VLU may appear impressive, but it’s not actually that demanding on the capability of the hardware.

Passing on from the circle of gluttons, Virgil leads Dante past the great foe of Plutus, a wolf-like creature who is chided by Virgil, and so they descend to the next circle, densely populated by avaricious misers and prodigal spendthrifts.

Plutus most probably refers here to a composite of the god of wealth, thus the root of the evil in these souls in this fourth circle of Hell, and Pluto, one of the gods of the classical underworld. Either of those roles justifies Dante’s description of him as the great enemy of mankind.

As opposites, the two groups of spirits are locked against one another, each rolling great boulders around in opposition. When their rocks crash together, they turn about and push in the other direction, and so on for eternity. Among those whose sin is avarice are many clerics, including cardinals and popes.

Virgil explains the role of Fortune in all this, that neither group of sinners can ever be satisfied with the riches that she has. Thus both the avaricious and the spendthrifts curse the angelic Fortune for their own sins.

Dante is led by Virgil past a dark spring to the swamp of the River Styx, so entering the fifth circle of Hell, where other souls covered in mud are attacking one another, punching and kicking as hard as they can. These are the sinners who were overcome with anger. Also in the swamp are their opposites, the mournful and miserable, whose breath bubbles up through the muddy waters.

The two reach the foot of a high tower, on top of which two flames are lit to signal to another tower in the far distance. This brings them a ferry, this time rowed by a man who Virgil calls Phlegyas, who is to carry the pair across the Stygian waters in his boat.

Phlegyas is a character drawn from classical legend and myth, including Virgil’s Aeneid. After Apollo raped his daughter Coronis, Phlegyas flew into a fit of rage and burned the temple of Apollo at Delphi, so the god killed him and sent him to the underworld to undergo eternal torment.

As Phlegyas rows Dante and Virgil across rough water, the spirit of Filippo Argenti, an arrogant Florentine who is hated by Dante, rises out of the water and tries to capsize their boat.

Dante tells him to be off, and Virgil assists in pushing him back into the river. They see Argenti’s ghost cast among those fighting on the shore, where he is torn apart by them, to Dante’s delight.

Their boat then approaches the moated city of Dis, in the depths of Hell (circles six to nine), where Phlegyas lands them. Virgil goes forward to secure their admission, but the gate to the city is slammed shut on him.

The artists

William Blake (1757–1827) was a British visionary painter and illustrator whose last and incomplete work was an illustrated edition of the Divine Comedy for the painter John Linnell. Most of his works shown in this series were created for that, although he did draw and paint scenes during his earlier career. I have a major series on his work here.

Gustave Doré (1832–1883) was the leading French illustrator of the nineteenth century, whose paintings are still relatively unknown. Early in his career, he produced a complete set of seventy illustrations for translations of the Inferno, which were first published in 1857 and continue to be used. These were followed in 1867 by more illustrations for Purgatorio and Paradiso. This article looks at his paintings.

References

Wikipedia
Danteworlds

Robin Kirkpatrick (trans) (2012) Dante, The Divine Comedy, Inferno, Purgatorio, Paradiso, Penguin Classics. ISBN 978 0 141 19749 4.
Richard Lansing (ed) (2000) The Dante Encyclopedia, Routledge. ISBN 978 0 415 87611 7.
Guy P Raffa (2009) The Complete Danteworlds, A Reader’s Guide to the Divine Comedy, Chicago UP. ISBN 978 0 2267 0270 4.
Prue Shaw (2014) Reading Dante, From Here to Eternity, Liveright. ISBN 978 1 63149 006 4.

I hope that you enjoyed Saturday’s Mac Riddles, episode 323. Here are my solutions to them.

1: Well-guarded like West Berlin was, it holds your greatest secrets.

2: Motor nerve processes your images.

3: Cloth or worsted to connect it all together.

The common factor

I look forward to your putting alternative cases.

At first sight, this might seem a simple question to answer. Allow me to demonstrate that it’s more complex, has changed over time, and still hasn’t been resolved.

Before 1984

Although there were exceptions, before the Mac most file systems that we were likely to encounter were simple. Each file consisted of stored data, together with a small entry in the file system’s metadata containing information such as the file’s name and its time and date of creation. By convention, as that’s not stored with the file’s data, that isn’t included in its size.

The only complication here was that storage is divided up into blocks, so in addition to the file’s actual size, we’d also want to know the total size taken by the storage blocks it used, as any given block couldn’t be shared between files, a figure often known as size on disk, and dependent on the size of those blocks. If the block size is 4,096 bytes, then any file whose data was equal to or smaller than that had a size on disk of 4,096 bytes, 4 KiB or 4.096 KB. (There are 1,000 bytes in a KB, but 1,024 bytes in a KiB.)

Classic Mac OS

One of the many innovations in the first Mac was its file system MFS, in which every file has two forks, one the traditional data fork, the other a resource fork for storing structured blobs of data termed resources. As MFS was replaced by HFS and eventually HFS+, those resource forks continued.

Resource forks often reached considerable sizes, and although they are stored separately from data forks in HFS+, Apple usually gave the sizes of the two forks, as shown in this dialog, where the size of the resource fork is 117,836 bytes, almost as large as the file’s 144,788 bytes of data. Information about the size of that file’s entry in the file system data, its attributes, wasn’t given, though.

HFS+ in Mac OS X

In the early years of Mac OS X, there was controversy as to whether it should continue supporting the use of resource forks, and most of their uses were replaced by flattened data files arranged in bundles. Nevertheless, in Mac OS X 10.4, HFS+ became multi-forked with what were dubbed extended attributes or xattrs, one type being com.apple.ResourceFork, the classic resource fork. However, the practice of giving separate sizes for the data fork and other forks died.

APFS

When APFS was released in 2017, it changed the way in which xattrs are stored, as explained here. Now, each file can consist of:

1. file system attributes, stored in the file system metadata structures;
2. small xattrs of up to 3,804 bytes, stored separately from its attributes, but in file system metadata;
3. large xattrs over 3,804 bytes, typically including any com.apple.ResourceFork, stored as data streams with separate records;
4. data, stored in storage blocks as set out in their file extents.

As demonstrated using crafted files, initially the Finder ignored items 1-3 in stating file size, and just gave that of 4, the data, although it could instead still have been including resource forks, of course.

The size of this text file is given as 391 bytes in the Finder’s Get Info in High Sierra, but as you’ll see below it contains over 90,000 bytes of extended attributes that figure simply ignores.

macOS Sequoia

Here are the sizes given for another of my specially crafted demonstration files, for APFS in macOS 15.6.1 Sequoia.

According to the Finder’s Get Info dialog, this file contains 263,195 bytes and occupies 266 KB on disk. On an SSD with the standard 4 KiB block size, that should be 65 blocks, or 266,240 bytes, as given correctly. There’s something amiss with that file, though, as it claims to be a Zip archive but has an image thumbnail.

Listing its xattrs using xattred reveals no less than 14, including two of 80 KB each. xattred claims it has a data fork size of 183,136 bytes and 161,406 bytes in xattrs, making a total size of 344,542 bytes, which is nowhere near that given by the Finder. (It’s the com.apple.ResourceFork xattr, a classic resource fork, that contains the image thumbnail displayed by QuickLook instead of the normal Zip file icon.)

To discover how the Finder arrives at a size of 263,195 bytes, we need to subtract the data size from that, making 80,059 bytes, the size of the file’s resource fork or com.apple.ResourceFork xattr. So, without being explicit about forks, it’s behaving the same as in Classic Mac OS. You might find that puzzling, given that there’s another xattr of the same size that it’s ignoring, and a dozen more that don’t get a look-in. As the use of com.apple.ResourceFork xattrs has long been discouraged if not deprecated, isn’t that a strange behaviour? The more so when modern xattrs that Apple has introduced relatively recently, such as com.apple.quarantine, com.apple.macl and com.apple.provenance, are ignored.

The deeper you look into this, the more puzzling it becomes. Here are the same file’s figures as shown in Precize.

Sizes are given a few lines down, from two sources, URL Keys and the file system (FileManager), and they also differ. There’s a list of xattrs given at the foot of this window, but that only gives 12 and ignores com.apple.ResourceFork and com.apple.FinderInfo.

In the macOS API, code can obtain values for file sizes from its URL. Two keys are available, fileSizeKey and totalFileSizeKey. The first gives the data size, and the second is the same ‘total’ as that shown by the Finder, i.e. data + com.apple.ResourceFork xattr, but excluding all other xattrs. Apple’s documentation explains those as:

• fileSize is “the total file size, in bytes”
• totalFileSize is “the total displayable size of the file, in bytes. The allocated size in bytes may include space used by metadata.”

FileManager also gives the data size in its FileAttributeKey.size, but doesn’t give any for xattrs, even com.apple.ResourceFork. The size of the Metadata shown for the File system is instead calculated by totalling the individual sizes of all its xattrs, including com.apple.ResourceFork and com.apple.FinderInfo.

This may appear to be nit-picking, but data sizes are given to the exact number of bytes, and the size on disk for non-sparse files should always be within 4,095 bytes of the data size. Yet accounting for xattrs remains rooted in Classic Mac OS from 25 years ago and still pretends that xattrs either don’t exist, or don’t take any space.

In the first article of this pair looking at paintings of windmills, I covered traditional views up to the first of the pre-Impressionists. This article takes this account from around 1850 up to the period between the two World Wars. Although the development of steam power during the nineteenth century brought great changes to many industries, windmills continued to flourish until the middle of the century, and even then they only declined gradually until the Second World War.

Samuel Palmer’s Summer Storm near Pulborough, Sussex from about 1851 refers to Dutch landscape painting, in a very Kentish context. A storm is seen approaching the rolling countryside near Pulborough, now in West Sussex. On the left, in the middle distance, a small bridge leads across to a hamlet set around a prominent windmill, whose blades are blurred as they are being driven by the rising wind.

Windmill styles differ outside northern Europe. When Jean-Léon Gérôme travelled down the River Danube in about 1855, he claimed to have witnessed this moving scene of Recreation in a Russian Camp, Remembering Moldavia (1855). A group of Russian soldiers in low spirits is being uplifted by making music, under the direction of their superior. Gérôme has captured an atmosphere which few of his other paintings achieved: the marvellous light of the sky, the skein of geese on the wing, and the parade of windmills in the distance, all draw together with the soldiers in their sombre greatcoats.

The following year, JC Dahl’s Burning Windmill at Stege is an unusual fire-painting following a traditional sub-genre of the Dutch Golden Age. Although painted well before Impressionism, Dahl echoes the red of the flames in the field and trees to the left of the windmill, and even in his signature.

During the winter of 1864, Johan Jongkind returned to the Netherlands, where he painted this Winter View with Skaters, which is more overtly pre-Impressionist.

Jongkind’s watercolour sketch of a Windmill at Antwerp of 1866 is even more painterly.

Claude Monet’s second visit to the Netherlands in 1874 ensured that The Windmill on the Onbekende Gracht, Amsterdam (1874) became a part of the history of Impressionism. This shows a windmill known as Het Land van Beloften, De Eendracht or De Binnen Tuchthuismolen, which was built in the late seventeenth century, and was moved from there to Utrecht just a couple of years after Monet painted it on the banks of the River Amstel.

Frits Thaulow’s painstakingly detailed View of Amerikavej in Copenhagen (1881) shows a windmill in the background, where it’s being used to provide power to the adjacent industrial site.

Volodymyr Orlovsky’s Ukrainian Landscape from 1882 shows one of the distinctive windmills on the elevated bank alongside a major river and its more populated floodplain to the right.

It may not have been Monet who first made the visual association between Dutch windmills and fields of tulips in flower, but his 1886 painting of Tulip Field in Holland must be its best-known depiction.

When Vincent van Gogh moved to Paris in 1886, he stayed with his brother Theo in Montmartre. He painted a series of marvellous views of the remaining windmills there, including the most famous of them all, Le Moulin de la Galette (1887), in whose gardens Renoir had painted his Bal du moulin de la Galette a decade earlier.

Paul Signac’s Rotterdam. The Windmill. The Canal. Morning (1906) is a Divisionist view of a windmill in the centre of this major port.

It was a Dutch painter who took windmills from Impressionism to the modernist styles of the twentieth century: Piet Mondrian.

Piet Mondrian’s gentle nocturne of Oostzijdse Mill on the River Gein by Moonlight from about 1903 is one of several views of windmills that he painted in Impressionist and post-Impressionist style.

When he started experimenting with vibrant colour and patterned brushstrokes in about 1908, this painting of a Mill in Sunlight marks his point of departure.

The Red Mill (1911) continues Mondrian’s move towards areas of flat colour. That year he left the windmills of Amsterdam and moved to Paris. To mark his move into the avant garde of that city, he dropped the second ‘a’ from his surname, going from Mondriaan to Mondrian. He became increasingly influenced by Georges Bracque and the Cubist works of Pablo Picasso, and the purely abstract paintings for which he remains well-known today.

Serhii Svitoslavskyi’s Ukrainian Landscape with Windmills, probably from about 1911, shows a small cluster of windmills with grazing livestock.

By the end of the First World War, milling grain had become more centralised, and the hundreds of thousands of small windmills across northern Europe lost their business. A few have been preserved, and some are still used for specialist products such as stoneground flour. But the unmistakable sight of a windmill on the skyline had been lost from much of the land.

During the 1930s, the Raviliouses started spending time in Sussex, where they became close friends with Peggy Angus, whose house The Furlongs at Beddingham, East Sussex, became a second home. Eric Ravilious became particularly fond of painting the chalk downs there, as in his Windmill (1934). This isn’t a windmill in the traditional sense, but a smaller wind-driven pump to extract water from the chalk, mainly for irrigation.

Unlike Apple’s bundled apps in macOS, the great majority of third-party software needs to run on more than just the latest version of macOS. This is a challenge when there’s a major redesign of the interface, as there is in macOS Tahoe. While OS 26 may bring greater consistency across platforms, it’s also important to developers and users that it doesn’t sacrifice consistency between, say, Sequoia and Tahoe.

As I showed recently in my simple little utility DropSum, at times the appearance of windows can be very different between macOS 15 Sequoia and 26 Tahoe. DropSum uses AppKit rather than SwiftUI, and is a little unusual in applying colour to its window. This is used in a popular mechanism to indicate when that window is ready to receive a file being held over it, by changing the view colour from systemOrange to systemGreen. As that coloured view extends over the controls in the window, I have had to be careful to ensure those controls remain readable in both appearance modes, with the Reduce transparency and Increase contrast settings in Accessibility settings, and across recent versions of macOS. That hasn’t proved easy, so what you see below appears to be the best compromise I can achieve. DropSum doesn’t alter its settings or behaviour between different versions of macOS, instead relies on the host API’s appearance modes and Accessibility settings.

Although I have confirmed the observations below on individual systems, to make comparison easier here each screenshot shows two DropSum windows. The upper is running in a Tahoe beta 7 VM (where the window title is left-aligned), and the lower in Sequoia 15.6.1 on the host (where the window title is centred).

Light mode

In both light appearance modes, all boxed text is displayed in black on a white background, making their contents and controls clear. There are marked differences in the hues seen, though, with both systemOrange and systemIndigo (chosen for better contrast in labels) being more intense in Tahoe than Sequoia. As expected, Tahoe’s controls are slightly larger, and the corners of all four text boxes are rounded rather than square.

Reducing transparency made little difference in either rendering, merely whitening the window title bar.

Increasing contrast changes the intensity of some colours. In Sequoia, systemOrange is lightened, and in both windows the traffic light buttons at the top left, and the Clear button, are darkened. Otherwise the most obvious effect is the outlining of all components, including each of the controls.

Apps built to support macOS 26 thus appear consistent between macOS 15 and 26 when used in light mode.

Dark mode

Most apparent here are the contrasting effects of dark mode on the background of the four text boxes. In Sequoia, their background is the systemOrange of the coloured view, but in Tahoe it’s black. The latter makes the text contents more readable, while unselected text in Sequoia is more difficult to read.

Increasing contrast has different effects on colours when in dark mode. In Sequoia all colours including the systemOrange view become slightly lighter, whereas in Tahoe the contrast of some is enhanced, with black becoming blacker and white whiter, but there’s little discernible change in systemOrange, which remains significantly more intense than in Sequoia. systemIndigo is rendered lighter though, making it more difficult to read against the systemOrange background.

Reduce transparency

Apple describes this effect as replacing “the transparent effect used on some backgrounds in macOS with a solid background to improve contrast and readability.” In both Sequoia and Tahoe, and in both appearance modes, the only effect observed is a lightening of the window title bar, as the rest of the window is already opaque.

Increase contrast

Apple describes this as increasing “the contrast of items on the screen (such as borders around buttons or boxes) without changing the contrast of the screen itself.” Although the borders are the most prominent effect in both versions of macOS and both appearance modes, there are also colour changes that aren’t consistent between Sequoia and Tahoe.

Conclusions

• Appearance modes in Tahoe exhibit different behaviours from those in Sequoia, most markedly in dark mode. In this example, Tahoe has the effect of enhancing readability in dark mode.
• Colour rendering of systemOrange also differs between Tahoe and Sequoia.
• Reduce transparency has little effect other than making transparent views opaque.
• Increase contrast primarily adds black (light mode) or white (dark mode) borders to controls, but its small colour changes, as seen here in Tahoe, may impair readability.
• Designing an interface that behaves consistently in both macOS Tahoe and older versions of macOS is a challenge that may not always work out. Developers need to assess their app’s human interface thoroughly in multiple macOS, appearance modes and Accessibility settings.

There seems to be some confusion over what windmills are, so this weekend I show a selection of paintings of them across Europe. This article covers the period between 1500-1850, when they remained popular. From the twelfth century until the twentieth, they were a common sight on many skylines in northern Europe. Preceding the better-known vertical windmills were various horizontal designs, and windmills continued to flourish until the middle of the nineteenth century. Used wherever there was a need for driving a rotating axle, they were widely employed to grind cereals into flour, power sawmills, make paper, grind materials, and thresh corn.

Hieronymus Bosch’s uniquely imaginative paintings often featured realistic background landscapes. One recurring setting is a city based on Antwerp or his home town of ‘s-Hertogenbosch, with a windmill closest to the viewer. This appears in the centre panel of his triptych The Adoration of the Magi from about 1490-1500, for instance.

A similar windmill appears in a slightly different setting in the version of The Temptation of Saint Anthony now in Lisbon, from around 1500-10, in its right wing. This is shown in the detail below.

The Bruegels also worked amid many windmills, but none seems so prominently out of place than in Pieter Bruegel the Elder’s Procession to Calvary from 1564. Windmills were commonly built on hills, where they would benefit from the most consistent wind, but this example on a towering crag is not only geographically inappropriate, but completely impractical. It stands on a circular platform to allow the mill to rotate according to the direction of the wind, but would hardly have been above Jerusalem at the time of the Crucifixion.

More at home are the half dozen windmills clustered around the port of Dordrecht in the Netherlands, shown in Jan van Goyen’s View of Dordrecht with the Grote Kirk Across the Maas from 1644.

Rembrandt painted few non-narrative landscapes, but among them is this dramatic view of The Mill (1645-48) seen in the rich rays of twilight.

The great masters of Dutch landscape art like Jacob van Ruisdael must have painted many hundreds of windmills, of which one of the best-known is this view of The Windmill at Wijk bij Duurstede from about 1670. This small town, now a city, is on the bank of the River Rhine, an ideal location for delivering grain by barge, and shipping the resulting flour. This should have kept the mill as busy as the wind allowed, and its owner prosperous.

This view of a Landscape with Windmills near Haarlem was painted by John Constable in 1830, almost two centuries after the original made by Jacob van Ruisdael.

Windmills were also a common sight along the lower reaches of the River Thames. William Hogarth’s print from his Industry and Idleness series shows its anti-hero Idle being rowed out to join his ship at Cuckold’s Point on the River Thames, opposite what were then the West Indian docks, between Limehouse and Greenwich. Long after these windmills had gone, this section of the river was still involved with the grain trade.

There were other windmills upstream of the city of London too. In what must be Thomas Girtin’s most famous painting of The White House at Chelsea, from 1800, the artist looks upstream of the River Thames from a location close to the modern Chelsea Bridge. The landmarks shown include, from the left, Joseph Freeman’s windmill (or Red House Mill), a horizontal air mill, the white house close to where Battersea Park is now, Battersea Bridge, and Chelsea Old Church. Girtin painted this when he was twenty-five, and showing greater promise than his rival JMW Turner. Two years later Girtin died of asthma.

A few years later the topographic painter John Varley painted this close-up view of the same Red House Mill, Battersea, Surrey, looking back in the opposite direction.

Some of the well-known windmills supplying the city of Paris with its flour were those above its outskirts on Montmartre Hill. Georges Michel’s view of The Mill of Montmartre was probably painted in about 1820, by which time there were only a few left.

Richard Parkes Bonington probably painted Barges on a River in around 1825-6 when he was travelling near the French town of Nantes. The windmill seen behind the trees is reminiscent of seventeenth-century Dutch landscape painting.

During his detailed realist period early in his career, Johan Jongkind painted this View of Maassluis in Winter (1848). Following the long tradition of landscape painting in the Netherlands, he sets his horizon low and paints a wonderful winter sky.