Bar chart of one identical Godot capture: 141 s through XWayland with vsync, 4.5 s with Godot's native Wayland driver, 1.2 s through XWayland with --disable-vsync.
Godot

A Godot screenshot tool ran 100× slower under XWayland until I passed –disable-vsync

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Offscreen automation windows on a Wayland desktop block about one second per frame on vsync. –disable-vsync took a capture from 141 s to 1.2 s.