UI/Qt+LibCore: Lock IOSurface for safe CPU reads on macOS#9257
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christianfrey wants to merge 1 commit intoLadybirdBrowser:masterfrom
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UI/Qt+LibCore: Lock IOSurface for safe CPU reads on macOS#9257christianfrey wants to merge 1 commit intoLadybirdBrowser:masterfrom
christianfrey wants to merge 1 commit intoLadybirdBrowser:masterfrom
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On macOS, SharedImageBuffer bitmaps are backed by IOSurface memory that may be written by the GPU. Qt reads this memory from the CPU side when creating a QImage and rendering it with QPainter. On Intel Macs, reading IOSurfaceGetBaseAddress() without first taking a read lock results in blank pages in the Qt UI. Add read-only IOSurface lock helpers and use them around the Qt rendering path to ensure proper synchronization between GPU writes and CPU reads.
christianfrey
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On Intel Macs, the IOSurface backing the Qt QImage may be updated by the GPU, but CPU access is not guaranteed to be coherent without explicit synchronization. This results in blank pages in the Qt UI.
This change adds lock_read_only() / unlock_read_only() around the Qt rendering path to ensure proper synchronization when reading from the IOSurface.
Apple Silicon is unaffected due to unified memory, but the locking is kept for correctness.