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Fix double-scaling by locking page layout to logical presentation

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Pages computed layout from SDL_GetWindowSize() (real window
coordinates) while SDL_SetRenderLogicalPresentation() independently
remapped every draw call into a 1920x1080 space. The two coordinate
systems only agreed when the window happened to be exactly 1920x1080;
at any other size, layout coordinates were transformed a second time,
so content shrank/grew quadratically toward the top-left on resize or
on non-1080p monitors. Commenting the call out masked the bug by
making rendering 1:1 with the window, but then nothing scaled: fonts
and margins stayed fixed-pixel while backgrounds cover-fit, and HiDPI
displays drew at point resolution and relied on blurry compositor
upsampling.

Restore SDL_SetRenderLogicalPresentation(1920x1080, LETTERBOX) as the
single source of scaling, and route all twelve layout sites through a
new radiantwave::getLayoutSize() helper (src/logical_size.h) that
returns the renderer's logical size, so pages always lay out against
the design resolution regardless of window or monitor geometry. Add
SDL_WINDOW_HIGH_PIXEL_DENSITY so HiDPI displays render at native pixel
density instead of being upscaled by the OS. Cached per-page textures
become resolution-independent since layout no longer depends on window
size.
This commit is contained in:
NeilClack
2026-08-21 09:29:23 -05:00
parent 8e930ef8d9
commit 3c9de0bee2
14 changed files with 47 additions and 18 deletions
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src/main.cpp
+6 -6
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@@ -62,12 +62,12 @@ SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[]) {
// Lock the renderer to a 1920x1080 logical coordinate space. All page
// layout code already targets this resolution, so everything renders at
// the correct size on any display — the GPU scales to native pixels.
// if (!SDL_SetRenderLogicalPresentation(state->renderer, 1920, 1080,
// SDL_LOGICAL_PRESENTATION_STRETCH)) {
// radiantwave::logger::Logger::instance().warning("Graphics",
// "Could not set logical render size; layout may be wrong on HiDPI
// displays");
// }
if (!SDL_SetRenderLogicalPresentation(state->renderer, 1920, 1080,
SDL_LOGICAL_PRESENTATION_STRETCH)) {
radiantwave::logger::Logger::instance().warning(
"Graphics", "Could not set logical render size; layout may be "
"wrong on HiDPI displays");
}
SDL_HideCursor();