# 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.