Swift’s native Clocks are very inefficient

Screenshot of Instruments showing the outline view for a Time Profile, expanded to show dozens of spurious, overhead functions taking up the vast majority of the runtime.

By which I mean, things like ContinuousClock and SuspendingClock. In absolute terms they don’t have much overhead – think sub-microsecond for most uses. Which makes them perfectly acceptable when they’re used sporadically (e.g. only a few times per second). However, if you need to deal with time and timing more frequently, their inefficiency can become… Read more

getBitmapDataPlanes can break NSImages & NSBitmapImageReps

Opaque black square.

Today was one of those days where you plan to real make a dent in your todo list, and end up spending the entire day debugging why the hell some images are suddenly rendering as completely opaque black. Long story short, on at least some bitmap images, as soon as you call getBitmapDataPlanes it somehow… Read more

Proactive Peek & Reveal on Edge Hover

Screen capture video showing an attempt to grab the scroll handle and how it's foiled by Proactive Peak stealing the click away to resize a previously-closed sidebar.

These are two misfeatures that appeared in macOS Sonoma (I believe). They are where a closed sidebar forces its way back into view temporarily, if the mouse comes to rest near the relevant edge of the window. It’s easy to see how some UI designer thought this was a good idea. Surely if you move… Read more

SwiftUI drag & drop does not support file promises

SwiftUI doesn’t offer anything equivalent to NSFilePromiseProvider, i.e. to write data to the drop destination. You have to ditch SwiftUI and use AppKit’s drag & drop APIs instead. FB13583826. Is that it? I know that’s not a very helpful in some sense, but I wasted days trying to figure out how to implement this very… Read more

Bad API example: FileManager’s url(for:in:appropriateFor:create:)

I find FileManager‘s url(for:in:appropriateFor:create:) to be very unintuitive. It seems to have multiple, largely-orthogonal functions. It can provide paths to common folders (albeit badly). It can create temporary folders. It can locate volume-specific bins (Trash folders). It is an example of bad API design. Specifically, regarding cohesion: the principle that an API should have one… Read more

NSImage is dangerous

Screenshot of an excerpt from Xcode's debug console showing the output of AddressSanitizer, having detected data race involving NSImage.

NSImage is formally documented as largely not thread-safe: The following classes and functions are generally not thread-safe. In most cases, you can use these classes from any thread as long as you use them from only one thread at a time. Check the class documentation for additional details. Apple’s Threading Programming Guide > Appendix A:… Read more