Every time Mac repainted a region we set imageLayer.contents to a new
CGImage. CALayer's default action for .contents is a 0.25s crossfade, so
big repaints (like after a click — cursor + button + window-focus) looked
like a pulse. Tap seemed "flickery"; actually the whole view was doing
quarter-second crossfades constantly, most just weren't big enough to
notice until a chunky repaint hit.
Override imageLayer.actions with NSNull for contents/contentsRect/frame/
transform so blits are instantaneous, and wrap apply() in a
CATransaction.setDisableActions(true) for safety.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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