Ctrl+wheel, Shift+wheel and the foreground slider each recoloured the whole
image synchronously, once per input event. On a large detector the recolour is
slower than the events arrive, so they queued up and the view lagged behind the
cursor for as long as the user kept scrolling.
Defer the recolour to a zero-delay single shot and drop the intermediate
values: at most one recolour is in flight, and it always uses the newest
foreground/background.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 5
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