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Dynamically size the fullscreen window; present design space via LETTERBOX
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SDL_CreateWindow hardcoded a 1920x1080 backbuffer while SDL_WINDOW_FULLSCREEN
let compositors run a different output mode; the mismatched buffer reached
the panel unscaled — quarter-size in the top-left on 4K sets, cropped ("4x
too large") on smaller non-1080p panels under cage/Wayland. Logical
presentation never got to map the fixed design space because its target
(the backbuffer) was pinned to stale dimensions.

Size the fullscreen window from SDL_GetCurrentDisplayMode so the first
commit already matches scanout 1:1, switch logical presentation to LETTERBOX
(aspect-safe bars on non-16:9 panels), and route both through new
kDesignWidth/kDesignHeight constants. Harden getLayoutSize() to always write
its out params and null-check the renderer/render-window before use.

Log requested/window/pixel-buffer/render-output sizes at startup and on
every resize event so field units self-diagnose this bug class into
~/.local/radiantwave/log.txt. SDL_WINDOW_HIGH_PIXEL_DENSITY stays off on
purpose: kiosk panels are not HiDPI, and keeping the pixel buffer equal to
the display mode keeps compositor scanout unscaled.
This commit is contained in:
NeilClack
2026-08-23 17:06:05 -05:00
parent 9e73c82641
commit 63265cc22f
2 changed files with 102 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/logical_size.h
+41 -7
View File
@@ -4,14 +4,48 @@
namespace radiantwave {
inline void getLayoutSize(SDL_Renderer* renderer, int* w, int* h)
// Design resolution every page lays out against. The renderer's logical
// presentation (LETTERBOX) scales this fixed space onto whatever
// window/backbuffer the display actually provides.
inline constexpr int kDesignWidth = 1920;
inline constexpr int kDesignHeight = 1080;
// Returns the size pages should lay out against: the renderer's logical size
// when presentation is active, otherwise the real window size. The output
// params are always written — design constants are the last-resort fallback.
inline void getLayoutSize(SDL_Renderer *renderer, int *w, int *h)
{
SDL_RendererLogicalPresentation mode = SDL_LOGICAL_PRESENTATION_DISABLED;
if (!SDL_GetRenderLogicalPresentation(renderer, w, h, &mode) ||
mode == SDL_LOGICAL_PRESENTATION_DISABLED || *w <= 0 || *h <= 0)
{
SDL_GetWindowSize(SDL_GetRenderWindow(renderer), w, h);
}
if (!w || !h)
return;
*w = kDesignWidth;
*h = kDesignHeight;
if (!renderer)
return;
SDL_RendererLogicalPresentation mode = SDL_LOGICAL_PRESENTATION_DISABLED;
int logicalW = 0;
int logicalH = 0;
if (SDL_GetRenderLogicalPresentation(renderer, &logicalW, &logicalH,
&mode) &&
mode != SDL_LOGICAL_PRESENTATION_DISABLED && logicalW > 0 &&
logicalH > 0) {
*w = logicalW;
*h = logicalH;
return;
}
SDL_Window *window = SDL_GetRenderWindow(renderer);
if (!window)
return;
int windowW = 0;
int windowH = 0;
SDL_GetWindowSize(window, &windowW, &windowH);
if (windowW > 0 && windowH > 0) {
*w = windowW;
*h = windowH;
}
}
} // namespace radiantwave