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sokol_android: setScreenHeight should use design height, not actual framebuffer height #158
Description
Problem
backends/sokol/templates/mobile.txt passes the runtime actual_h from window.height() to g.setScreenHeight() in the frame() callback:
// mobile.txt — broken
const actual_h = window.height();
BackendGfxType.setScreenSize(actual_w, actual_h);
g.setScreenHeight(@floatFromInt(actual_h)); // ← should use design heightOn Android with high_dpi = false (sokol default), window.height() returns half the physical pixel height (e.g. 540 on a 1080px screen). The renderer uses this as its logical screen height, so renderer.toScreenY(design_h) computes a negative value and screen-space background sprites appear off-screen.
Fix
The template already declares screen_h: u32 = {{height}} (the project design height). Use it for setScreenHeight while setScreenSize continues to receive the actual framebuffer dimensions:
// mobile.txt — fixed
const actual_w = window.width();
const actual_h = window.height();
BackendGfxType.setScreenSize(actual_w, actual_h); // gfx backend: actual pixels for NDC
g.setScreenHeight(@as(f32, @floatFromInt(screen_h))); // renderer: design height for world→screen YFile
backends/sokol/templates/mobile.txt, line 30.
Impact
All Android projects using the sokol backend where screen-space (background/UI) sprites are positioned using the design height.
Activity
fix(sokol/android): camera Y-convention and design height for setScre…
apotema commentedon Apr 17, 2026
Fix landed in labelle-toolkit/labelle-assembler#24 after the sokol backend was ejected from labelle-cli to labelle-assembler (via #150). Verified on current assembler
main:backends/sokol/src/gfx.zig:208-219(toNdcY uses(py - cam.target.y) * cam.zoom + cam.offset.y)backends/sokol/templates/mobile.txt:42(g.setScreenHeight(@floatFromInt(screen_h)))window.zig:130(high_dpi = true),mobile.txt:41(setDesignSize),mobile.txt:48(zoom = actual_h/design_h),mobile.txt:52(frameDuration()dt)ci: build labelle-assembler from the #217 branch for delegation tests
ci: track labelle-assembler main now that #217 landed there
Make labelle-cli a thin driver over the assembler binary (#217) (#221)