Resizing is strangely broken on Windows

reuk · January 20, 2026, 12:03pm

Thanks for reporting. A fix for this issue has been published:

HWNDComponentPeer: Avoid glitches and sluggishness during live resize

committed 10:55AM - 20 Jan 26 UTC

258203706cdfc1357effe8cc752672b793cea37d introduced a problem where live-resize …of a window would cause the window content to flash and slow down. The cause of the errant behaviour seems to be that, during resize, many WM_PAINT messages might be dispatched over the course of a single vblank interval. Then, each of these paint calls was waiting for the next vblank interval to display. This additional waiting resulted in sluggishness, since many frames would have to be presented before the presentation 'caught up' with the current window size. This also meant that many consecutive frames were presented with stale window size information. The solution added here simply checks whether we're live resizing, and uses the vblank instead of WM_PAINT to synchronise repaints during the resize operation.

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Resizing is strangely broken on Windows

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