fix(screen-adapter): debounce resize handler to prevent black flicker on web#19186
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fix(screen-adapter): debounce resize handler to prevent black flicker on web#19186UC-RX0 wants to merge 1 commit into
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… on web The window resize event listener was calling _updateFrame() synchronously on every resize event. During continuous window dragging, this triggered dozens of swapchain/backbuffer reallocations per second, each producing a blank frame. This change: - Adds _resizeTimeoutId field for debounce state tracking - Debounces the resize handler using setTimeout with EVENT_TIMEOUT (200ms) - Uncomments and enables the handleResizeEvent guard on the resize path - Adds handleResizeEvent guard to the DPR matchMedia listener, which was previously bypassing it Fixes: cocos#19182
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Code Size Check Report
Interface Check ReportThis pull request does not change any public interfaces ! |
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Problem
On Web builds, continuously resizing the browser window produces rapid black flickering. Each
resizeevent synchronously calls_resizeFrame()→_updateContainer()→emit('window-resize'), which triggers a swapchain/backbuffer reallocation. During a continuous drag this fires dozens of times per second, each producing a blank (black) frame before the next render.The same continuous-resize test does not flicker in Cocos Creator 2.x (because v2 keeps a fixed backbuffer and CSS-scales it rather than reallocating on every resize).
Root Cause
In
pal/screen-adapter/src/web/screen-adapter.ts, theresizeevent handler (line 380) had no debounce, unlike theorientationchangehandler (line 407) which already usesEVENT_TIMEOUT(200ms) +setTimeout.Additionally, the DPR
matchMediachange listener (line 397) emittedwindow-resizedirectly, bypassing:handleResizeEventguard (used byview.resizeWithBrowserSize(false))Fix
Debounce the resize handler — Added a
_resizeTimeoutIdfield and debounce logic using the sameEVENT_TIMEOUT(200ms) pattern already used by the orientation change handler. Rapid resize events cancel the pending timeout and restart it; only the last event after the drag stops triggers_resizeFrame().Gate DPR matchMedia handler — Added
handleResizeEventcheck before emittingwindow-resize, consistent with the resize and orientation handlers.Changes
pal/screen-adapter/src/web/screen-adapter.ts: +11/-1 lines_resizeTimeoutIdprivate field_resizeFrame()call insidesetTimeout/clearTimeoutdebouncehandleResizeEventguard to DPR matchMedia listenerSide Effects
_resizeFrame()→_updateContainer()edit-box-impl.ts(temporarily disables handleResizeEvent)view.resizeWithBrowserSize(false)Fixes: #19182
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