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+# Session Log — 2026-08-08
+
+## Fullscreen Texture Viewer — Verification and RHI Fixes
+
+Continuation of the fullscreen-blit plan (`documents/plans/fullscreen-blit.md`),
+which rewrote `main.cpp` from the Suzanne mesh demo into a bindless texture
+viewer with contain-fit. This session visually verified the renderer and fixed
+three real bugs uncovered by that verification.
+
+### Verification method
+
+- Ran the app under the X11 SDL driver (`SDL_VIDEODRIVER=x11`) and captured the
+  window with `xwd -id <window>`, then sampled pixels with ImageMagick
+  (`magick -format "%[pixel:p{x,y}]" info:`). The model cannot view images, so
+  all render checks were programmatic (pure-black bars, centered content).
+- XTEST synthesised keys (`XTestFakeKeyEvent`) are silently dropped by
+  KWin/XWayland (confirmed with `xev`: FocusIn arrives via `_NET_ACTIVE_WINDOW`,
+  KeyPress never does). So texture cycling could not be driven headlessly; fit
+  cases were verified by temporarily making each texture the initial selection.
+
+### Contain-fit verified (pixel-sampled)
+
+| Texture             | Window    | Result                                |
+|---------------------|-----------|---------------------------------------|
+| square 1024x1024    | 16:9      | pillarbox (black L/R bars)            |
+| test_wide 2048x512  | 16:9      | letterbox (black T/B bars)            |
+| test_tall 512x2048  | 16:9      | pillarbox (black L/R bars)            |
+| test_fill 1920x1080 | 16:9      | fills exactly (no bars)               |
+| square, then resized to portrait | portrait | fit recomputed per frame → flips to letterbox |
+
+### Bugs found and fixed
+
+1. **`VK_SUBOPTIMAL_KHR` crashed the app.** `prRhiAcquireNextImageVk` and
+   `prRhiPresentVk` routed SUBOPTIMAL into `_checkVk` → `__builtin_trap()`
+   (SIGILL, caught under X11 immediately). Both now return
+   `PR_RHI_SWAPCHAIN_OUT_OF_DATE` for SUBOPTIMAL, same as OUT_OF_DATE
+   (`pr_rhi_vk.c`).
+2. **Swapchain recreate ignored surface extent.** `prRhiRecreateSwapchainVk`
+   hard-coded the passed width/height. Now queries
+   `vkGetPhysicalDeviceSurfaceCapabilitiesKHR` and falls back to the passed
+   size only when `currentExtent == 0xFFFFFFFF` (matches the initial-create
+   logic).
+3. **App used logical window size for the swapchain.** Under HiDPI the drawable
+   differs from `SDL_GetWindowSize` (1920x1080 logical vs 2400x1350 drawable at
+   1.25x scale on XWayland) — the root cause of #1. main.cpp now uses
+   `SDL_GetWindowSizeInPixels` for swapchain width/height, the fit rect, the
+   viewport, and the scissor.
+
+### CLI arg considered and removed
+
+Added a `--texture N` startup arg to drive the verification, then removed it at
+the user's request (`main()` is back to no-args, `app.selected = 0`). If
+headless key injection is ever needed again, revisit (e.g. `ydotool`/`wtype` on
+Wayland, or a WM on a real X server).
+
+### Notes
+
+- `main.cpp` header comment, `<cstdlib>` include, and plan doc all updated to
+  reflect the removed arg.
+- Native Wayland run still clean after all fixes; `just build` passes.