tracking: text rendering quality at small sizes (upstream gg#174)

[kolkov]

Summary

Text labels at 12-16px (standard UI sizes) have inconsistent stroke weight — visible in hello example on "Dark mode", "Enable notifications", radio labels. Root cause is in gg's MSDF pipeline.

Upstream Tracking

All implementation work happens in gg: gogpu/gg#174

UI Integration Plan

Once gg delivers the TextMode API (TEXT-QUALITY-004) and GPU vector text (TEXT-QUALITY-005), the UI renderer will:

1. Set ctx.SetTextMode(gg.TextModeVector) for quality-first rendering
2. Propagate DPI scale factor from window to gg context
3. Optional: per-widget text mode (animated counters -> MSDF for performance)

Expected Timeline

• Phase 0 (gg): MSDF tuning — immediate improvement, no UI changes needed
• Phase 1 (gg): DPI scaling — UI passes scale factor
• Phase 2 (gg + ui): TextMode API — UI sets Vector mode
• Phase 3 (gg): Hinting + regression tests

Related

• tracking: enterprise text rendering quality — dual-strategy architecture gg#174 — upstream tracking issue
• Internal: TASK-UI-056, TEXT-QUALITY-003 (font system)

[kolkov]

Progress Update (2026-03-12)

Done (PR #43)

MSDF quality fix (upstream):
Stem darkening in gg v0.35.0 fixed MSDF stroke thickness inconsistencies at 12-16px. MSDF now renders quality text even at 10-12px. TextModeAuto (default) provides excellent results.

TextModeVector investigation:
Investigated and found incompatible with GPU surface rendering — drawStringAsOutlines routes through CPU pixmap which isn't composited in surface mode. Not needed thanks to stem darkening.

Font upgrade:
Replaced Go fonts (goregular/gobold) with Inter — professional UI typeface (GitHub, Figma, VSCode). Inter Regular (400) + Bold (700) embedded via //go:embed (+136KB, latin subset).

Dependencies:

• gg v0.35.1 → v0.35.3 (MSDF FontID collision fix, Retina drift fix)
• gogpu v0.23.1 → v0.23.2 (Retina contentsScale fix)

Remaining

• Upstream gg#174 still open — may deliver further text quality improvements
• DPI scale pass-through to text rendering (verify correct usage)
• Per-widget text mode (future, if needed)

Related tasks completed

• TASK-UI-056: TextMode Integration — resolved (stem darkening, no UI changes needed)
• TEXT-QUALITY-003: Professional Font System (Inter) — done

[kolkov]

Update: gg v0.36.0 shipped with significant text rendering improvements:

• GPU GlyphMask cache (Tier 6) — CPU rasterization via AnalyticFiller with 256-level AA, R8 alpha atlas, GPU compositing via textured quads. Subpixel positioning with 16 variants per glyph.
• Font hinting integration — auto-hinting for text <= 48px, grid-fits outlines to pixel boundaries
• ClearType LCD subpixel rendering — 3x horizontal oversampling with 5-tap FIR LCD filter

gogpu/ui has been updated to gg v0.36.0. Visual testing on the signals demo shows clean text rendering at standard UI sizes (12-16px). The GlyphMask mode auto-selects for text <= 48px, which covers all UI label sizes.

Keeping open until we verify across platforms (macOS, Linux) and confirm gg#174 is fully resolved upstream.

[kolkov]

Update: gg now uses FilterModeNearest for the GlyphMask bitmap atlas sampler (commit 481cd2d). This significantly improves text sharpness on Vulkan and DX12 — bitmap glyphs are no longer blurred by linear interpolation.

On GLES, text is still blurry because the GlyphMask pipeline doesn't activate (likely due to hardcoded TextureFormatBGRA8Unorm in glyph_mask_pipeline.go — GLES surface may be RGBA8). Tracked as BUG-GG-005 in gg kanban.

The fix will ship with the next gg release.

[cdlus]

Nice, I was having the same issue. Can't wait for the fix that solves it.