Recover from WebGL context loss on Safari and other browsers#225
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The postprocessing EffectComposer reads `renderer.getContext().getContextAttributes().alpha` when its renderer or passes are set. When the browser drops the WebGL context — common on Safari/WebKit under GPU pressure, with many live contexts, or on tab restore — `getContextAttributes()` returns null and the access throws "null is not an object", crashing the viewport. Add a useWebGLContextLost hook that tracks webglcontextlost/restored on the R3F canvas (calling preventDefault so the browser attempts restoration), and gate the EffectComposer on it so post-processing tears down while the context is gone and remounts cleanly on restore. Nudge a repaint on restore since the viewport uses a demand frameloop. https://claude.ai/code/session_019HGPK77WwjeXuD7wFdNF1W
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Summary
Fixed a viewport crash that occurs when the browser drops the WebGL context, which is especially common on Safari under GPU memory pressure, when too many live contexts exist, or when a tab is backgrounded and restored. The post-processing pipeline now gracefully tears down while the context is lost and remounts cleanly once the browser restores it.
Changes
New hook:
useWebGLContextLost— Tracks whether the viewport's WebGL context is currently lost by listening towebglcontextlostandwebglcontextrestoredevents. CallspreventDefault()on context loss to signal intent to recover, which triggers the matching restore event. Handles edge cases like contexts lost before listeners attach andgetContext()throwing on half-torn-down renderers.Updated
ViewportContent— Conditionally unmounts the post-processing EffectComposer while the context is lost (it crashes readingrenderer.getContext().getContextAttributes().alphaoff a dead context). Triggers a repaint viainvalidate()when the context is restored, since the viewport runs on demand frameloop and would otherwise sit blank until the next user interaction.Changelog entry — Documents the fix for version 0.9.4.
Implementation Details
The hook seeds initial state by checking
gl.isContextLost()in case the context was already lost before listeners attached (e.g., created on a backgrounded tab). The viewport's conditional rendering of post-processing ({engineReady && !xrPresenting && !contextLost && ...}) ensures fragile GPU-dependent subtrees are safely unmounted during context loss and remounted once Three.js's WebGLRenderer re-initializes its GL state on restore.https://claude.ai/code/session_019HGPK77WwjeXuD7wFdNF1W