High-performance text rendering for Go. Shaping, layout, rasterization, and editing live in one package. Text shaping and rasterization are pure Go on all native platforms. No C libraries or system text APIs are required for the core library.
| OS | Shaper | Rasterizer |
|---|---|---|
| Linux | HarfBuzz (go-text) | x/image/vector |
| macOS | HarfBuzz (go-text) | x/image/vector |
| iOS | HarfBuzz (go-text) | x/image/vector |
| Windows | HarfBuzz (go-text) | x/image/vector |
| Android | HarfBuzz (go-text) | x/image/vector |
| WASM | Canvas2D | Canvas2D |
The glyph package builds with CGO_ENABLED=0 on all platforms. CGo is only
used by the optional GPU rendering backends (backend/gpu, backend/ios,
backend/android) to reach native graphics APIs (Metal, OpenGL, GLES).
go get github.com/go-gui-org/go-glyph@latestts, err := glyph.NewTextSystem(backend)
if err != nil {
log.Fatal(err)
}
defer ts.Free()
ts.DrawText(x, y, "Hello, World!", glyph.TextConfig{
Style: glyph.TextStyle{FontName: "Sans 24", Color: glyph.Color{A: 255}},
})
ts.Commit() // Call once per frame, after all draw calls.For repeated draws, shape once with LayoutText or LayoutRichText. Then draw
the cached Layout each frame. See the
package docs for the full
API.
Shaping and layout
- HarfBuzz shaping with ligatures and combining-mark positioning.
- Bidirectional text (UAX #9) with per-paragraph direction.
- Word segmentation by rune class, with standalone helpers that need no
Layout. - Line wrap (word, char, word-char), CJK breaks (UAX #14), alignment, indent, line spacing, tab stops.
- Vertical text flow for CJK.
- OpenType feature tags and variable-font axes.
- Pango markup (
<b>,<i>,<span>, and more). - Rich text with per-run styles, plus inline-object placeholders.
Rendering
- Glyph atlas with sub-pixel bins, dirty-rect uploads, and a glyph cache.
- N-stop gradients (horizontal, vertical, diagonal).
- Strokes, underlines, strikethroughs, background highlights.
- Color emoji (CBDT/sbix bitmaps, COLR v0) with text/color presentation rules (VS15/VS16).
- Procedural box-drawing and block elements for gap-free TUI frames. Grid
callers set
CellWidth/CellHeightfor exact joins. - Affine transforms (rotate, skew, scale) and per-glyph placements for text on a path.
InkBoundsreports the painted box for centering icons and marks.
Editing and input
- Grapheme-aware mutation helpers (
InsertText,DeleteBackward,DeleteForward, selection ops). UndoManagerwith time-based coalescing.- IME preedit state (
CompositionState) with clause styling and cursor rendering, plus transformed variants that follow rotated text. - Hit testing, cursor geometry, word/paragraph queries, selection rects, and cursor motion (char, word, line, vertical with preferred x).
| Backend | Target | Module |
|---|---|---|
backend/ebitengine |
Ebitengine | Separate module |
backend/gpu |
OpenGL 3.3 / Metal | Main module |
backend/web |
HTML Canvas (WASM) | Main module |
backend/android |
GLES | Main module |
backend/ios |
Metal | Main module |
backend/ebitengine keeps its own go.mod so the root module stays free of the
Ebiten dependency. The import path is unchanged. Custom backends implement
DrawBackend (plus the optional RectTextureUpdater and
TransformedFillBackend extensions).
System fonts load per OS (macOS, Linux with XDG dirs, Windows with
%SystemRoot% fallback, Android /system/fonts). Use AddFontFile or
AddFontBytes (go:embed friendly) for app fonts, including .ttc collections.
ResolveFontName shows the resolved family. ListFontFamilies enumerates
registered families. Fallback faces scale by cap-height ratio so CJK and icon
glyphs match the primary size. On WASM, use the browser FontFace API instead of
AddFontBytes.
Pair (*TextSystem).SetDPIScale with SetDPIScale on the backend when the
window moves to a display with a new scale factor. The call is a no-op when the
value is unchanged or out of range, so resize handlers can call it each frame.
Call Purge after a full clear to reclaim layout, glyph, and atlas memory
without tearing down the TextSystem.
Context, Renderer, TextSystem, GlyphAtlas, and UndoManager are not
safe for concurrent use. Call all glyph methods from the main/render goroutine.
The package performs no internal locking by design.
Each directory under examples/ is its own module: demo, demo_gpu,
showcase_gpu, showcase_web, showcase_android, showcase_ios,
showcase_sections.
See LICENSE.