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.
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.
NeilClack