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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:generate go run gen.go
// Package basicfont provides fixed-size font faces.
package basicfont // import ""
import (
// Range maps a contiguous range of runes to vertically adjacent sub-images of
// a Face's Mask image. The rune range is inclusive on the low end and
// exclusive on the high end.
// If Low <= r && r < High, then the rune r is mapped to the sub-image of
// Face.Mask whose bounds are image.Rect(0, y*h, Face.Width, (y+1)*h),
// where y = (int(r-Low) + Offset) and h = (Face.Ascent + Face.Descent).
type Range struct {
Low, High rune
Offset int
// Face7x13 is a Face derived from the public domain X11 misc-fixed font files.
// At the moment, it holds the printable characters in ASCII starting with
// space, and the Unicode replacement character U+FFFD.
// Its data is entirely self-contained and does not require loading from
// separate files.
var Face7x13 = &Face{
Advance: 7,
Width: 6,
Height: 13,
Ascent: 11,
Descent: 2,
Mask: mask7x13,
Ranges: []Range{
{'\u0020', '\u007f', 0},
{'\ufffd', '\ufffe', 95},
// Face is a basic font face whose glyphs all have the same metrics.
// It is safe to use concurrently.
type Face struct {
// Advance is the glyph advance, in pixels.
Advance int
// Width is the glyph width, in pixels.
Width int
// Height is the inter-line height, in pixels.
Height int
// Ascent is the glyph ascent, in pixels.
Ascent int
// Descent is the glyph descent, in pixels.
Descent int
// Left is the left side bearing, in pixels. A positive value means that
// all of a glyph is to the right of the dot.
Left int
// Mask contains all of the glyph masks. Its width is typically the Face's
// Width, and its height a multiple of the Face's Height.
Mask image.Image
// Ranges map runes to sub-images of Mask. The rune ranges must not
// overlap, and must be in increasing rune order.
Ranges []Range
func (f *Face) Close() error { return nil }
func (f *Face) Kern(r0, r1 rune) fixed.Int26_6 { return 0 }
func (f *Face) Metrics() font.Metrics {
return font.Metrics{
Height: fixed.I(f.Height),
Ascent: fixed.I(f.Ascent),
Descent: fixed.I(f.Descent),
XHeight: fixed.I(f.Ascent),
CapHeight: fixed.I(f.Ascent),
CaretSlope: image.Point{X: 0, Y: 1},
func (f *Face) Glyph(dot fixed.Point26_6, r rune) (
dr image.Rectangle, mask image.Image, maskp image.Point, advance fixed.Int26_6, ok bool) {
for _, rr := range [2]rune{r, '\ufffd'} {
for _, rng := range f.Ranges {
if rr < rng.Low || rng.High <= rr {
maskp.Y = (int(rr-rng.Low) + rng.Offset) * (f.Ascent + f.Descent)
ok = true
break loop
if !ok {
return image.Rectangle{}, nil, image.Point{}, 0, false
x := int(dot.X+32)>>6 + f.Left
y := int(dot.Y+32) >> 6
dr = image.Rectangle{
Min: image.Point{
X: x,
Y: y - f.Ascent,
Max: image.Point{
X: x + f.Width,
Y: y + f.Descent,
return dr, f.Mask, maskp, fixed.I(f.Advance), true
func (f *Face) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) {
return fixed.R(0, -f.Ascent, f.Width, +f.Descent), fixed.I(f.Advance), true
func (f *Face) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) {
return fixed.I(f.Advance), true