Five years ago, in the year of our lord 2014, I wrote about the difficulties of drawing bitmapped graphics to screen in macOS, and I revisited that issue again in the winter of 2017.

Now, I bring you what is hopefully the final installment (posted here for usefulness to the internet-at-large).

To recap: drawing bitmapped graphics to screen was relatively fast in macOS 10.6 using the obvious APIs (CoreGraphics/Quartz/etc), and when drawing to non-retina, normal displays in newer macOS versions. Drawing bitmapped graphics to (the now dominating) Retina displays, however, got slow. In the case of a Retina Macbook Pro, it was a little slow. The 5k iMacs display updates are excruciatingly slow when using the classic APIs (due to high pixel count, and expensive conversion to 30-bit colors which these displays support).

The first thing I looked at was the wantsLayer attribute of NSView:

• If you use "mynsview.wantsLayer = YES", things get better. On normal displays, slightly, on a Retina Macbook Pro's display, quite a bit better. On a 5k iMac's display, maybe slightly better. Not much.
• Using the wantsLayer attribute seems to be supported on 10.6-current.
• For views that use layers, you can no longer [NSView lockFocus] the view and draw into it out of a paint cycle (which makes sense), which prevents us from implementing GetDC()/ReleaseDC() emulation.

• If you want to update the entire view every time, you can configure a CAMetalLayer properly and just shove your bits into the CAMetalLayer's texture and tell it to present and avoid having to create another texture and a render pipeline and all of that nonsense.
• If you want to do partial window updates (partial-invalidates, or a GetDC()-like draw), then you have to create a whole render pipeline, a texture, compile shaders, blah blah blah ugh.
• There's a bunch more work that needs to get done to make it all work (and adapt to changing GPUs, blah blah blah)...