fix(terminal): prevent crash during resize with high-output programs#114
fix(terminal): prevent crash during resize with high-output programs#1140xBigBoss wants to merge 2 commits intocoder:mainfrom
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Fixes a race condition that causes crashes when resizing the terminal while programs with high output (like cmatrix, htop) are running. The issue occurs because the render loop and write operations can access WASM memory buffers while resize() is reallocating them, causing SIGSEGV crashes. This fix implements three protections: 1. **Pause render loop during resize**: Cancel the animation frame before WASM resize and restart after, preventing concurrent buffer access. 2. **Invalidate cached buffer views**: Clear graphemeBuffer and graphemeBufferPtr when invalidating buffers, since TypedArray views become detached when underlying memory is reallocated. 3. **Queue writes during resize**: Buffer incoming PTY data during resize and flush after a frame, preventing writes from hitting WASM while buffers are being reallocated. All three protections are needed to fully prevent the race condition with rapidly-outputting programs.
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| this.resizeFlushFrameId = requestAnimationFrame(() => { | ||
| this.resizeFlushFrameId = undefined; | ||
| this.isResizing = false; | ||
| this.flushWriteQueue(); |
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isResizing is only cleared inside a requestAnimationFrame callback, so after any resize in a background/hidden tab (where rAF is paused or heavily throttled) every subsequent write() stays queued and never reaches WASM until the tab becomes visible again. In high-output sessions this causes apparent terminal hangs and unbounded writeQueue growth, which is a production-impacting regression for embedded terminals that keep running while not foregrounded.
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Summary
Fixes a race condition that causes crashes when resizing the terminal while programs with high output (like cmatrix, htop) are running.
The issue occurs because the render loop and write operations can access WASM memory buffers while
resize()is reallocating them, causing SIGSEGV crashes.Changes
This PR implements three protections:
Pause render loop during resize: Cancel the animation frame before WASM resize and restart after, preventing concurrent buffer access.
Invalidate cached buffer views: Clear
graphemeBufferandgraphemeBufferPtrwhen invalidating buffers, since TypedArray views become detached when underlying memory is reallocated.Queue writes during resize: Buffer incoming PTY data during resize and flush after a frame, preventing writes from hitting WASM while buffers are being reallocated.
All three protections are needed to fully prevent the race condition with rapidly-outputting programs.
Testing
cmatrix- no longer crashesFiles Changed
lib/terminal.ts- Main resize protection logiclib/ghostty.ts- Buffer invalidation for graphemeBuffer