On a machine with Iris Xe and a discrete GPU the default request can pick
the discrete one, so the probe would not test the affected adapter.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
wgpu-hal 30 creates Iris Xe textures as committed resources (its
gfx-rs/wgpu#3552 workaround) with D3D12_HEAP_FLAG_CREATE_NOT_ZEROED, and
egui-wgpu fills each new texture with a single copy. On this driver the
copy leaves 4x4 blocks of all-zero texels showing stale memory, so the
empty corners of Brush Preset picker strokes and tool icons show freed
textures' pixels (often red).
ui-egui's new texel_guard plugin rewrites fully transparent texels in
each frame's texture uploads as premultiplied (0, 0, 0, 1) before eframe
renders them (under one 8-bit level of difference). The desktop app
installs it only for DX12 on "Iris(R) Xe", the same adapter test wgpu
uses; PHOTOCRAFT_TEXEL_GUARD=1/0 forces it on or off.
The gpu example zero_block_probe reproduces the driver bug without the
UI: 630/1500 egui-style uploads read back wrong, 0/1500 with the guard.
Driving the release app (tool cycling, picker rescaled): 6/40
screenshots with red blocks before, 0/120 after.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
* perf(gpu): reuse unchanged lower-stack composite chunks
* test(gpu): verify half-float composite checkpoint reuse
* docs: record measured GPU composite reuse gains and limits
* perf(gpu): admit whole grid chunks, serve partial damage as sub-rect copies
Cache entries were keyed by the exact damage rectangle, so brush strokes
(a new partial rect every frame) filled the budget with entries that
never hit again. Entries are now whole chunk-aligned, chunk-sized grid
cells: a capture merges into the cell it overlaps at the rectangle's
offset, a read is served as a sub-rect copy of the covered part, and
coverage is tracked per cell so a resume only happens where every pixel
of the requested rectangle is cached. After a full render, any in-bounds
partial rectangle hits.
Regression test: two series of disjoint strokes inside the same chunks
leave composite_cache_bytes unchanged (no entry-per-rectangle growth),
a full refresh still finds its chunks and a top-layer edit afterwards
reuses them. The old partial-damage test now expects the covered-chunk
hit and checks outside-the-document renders admit nothing.
* docs: record the GPU reuse measurement in target-app-parity.md
The honest assessment moved from roadmap.md to target-app-parity.md on
main; keep main's roadmap and add only the dated measurement.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---------
Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
