1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:generate go run gen.go
6
7// Package basicfont provides fixed-size font faces.
8package basicfont // import "golang.org/x/image/font/basicfont"
9
10import (
11	"image"
12
13	"golang.org/x/image/font"
14	"golang.org/x/image/math/fixed"
15)
16
17// Range maps a contiguous range of runes to vertically adjacent sub-images of
18// a Face's Mask image. The rune range is inclusive on the low end and
19// exclusive on the high end.
20//
21// If Low <= r && r < High, then the rune r is mapped to the sub-image of
22// Face.Mask whose bounds are image.Rect(0, y*h, Face.Width, (y+1)*h),
23// where y = (int(r-Low) + Offset) and h = (Face.Ascent + Face.Descent).
24type Range struct {
25	Low, High rune
26	Offset    int
27}
28
29// Face7x13 is a Face derived from the public domain X11 misc-fixed font files.
30//
31// At the moment, it holds the printable characters in ASCII starting with
32// space, and the Unicode replacement character U+FFFD.
33//
34// Its data is entirely self-contained and does not require loading from
35// separate files.
36var Face7x13 = &Face{
37	Advance: 7,
38	Width:   6,
39	Height:  13,
40	Ascent:  11,
41	Descent: 2,
42	Mask:    mask7x13,
43	Ranges: []Range{
44		{'\u0020', '\u007f', 0},
45		{'\ufffd', '\ufffe', 95},
46	},
47}
48
49// Face is a basic font face whose glyphs all have the same metrics.
50//
51// It is safe to use concurrently.
52type Face struct {
53	// Advance is the glyph advance, in pixels.
54	Advance int
55	// Width is the glyph width, in pixels.
56	Width int
57	// Height is the inter-line height, in pixels.
58	Height int
59	// Ascent is the glyph ascent, in pixels.
60	Ascent int
61	// Descent is the glyph descent, in pixels.
62	Descent int
63	// Left is the left side bearing, in pixels. A positive value means that
64	// all of a glyph is to the right of the dot.
65	Left int
66
67	// Mask contains all of the glyph masks. Its width is typically the Face's
68	// Width, and its height a multiple of the Face's Height.
69	Mask image.Image
70	// Ranges map runes to sub-images of Mask. The rune ranges must not
71	// overlap, and must be in increasing rune order.
72	Ranges []Range
73}
74
75func (f *Face) Close() error                   { return nil }
76func (f *Face) Kern(r0, r1 rune) fixed.Int26_6 { return 0 }
77
78func (f *Face) Metrics() font.Metrics {
79	return font.Metrics{
80		Height:     fixed.I(f.Height),
81		Ascent:     fixed.I(f.Ascent),
82		Descent:    fixed.I(f.Descent),
83		XHeight:    fixed.I(f.Ascent),
84		CapHeight:  fixed.I(f.Ascent),
85		CaretSlope: image.Point{X: 0, Y: 1},
86	}
87}
88
89func (f *Face) Glyph(dot fixed.Point26_6, r rune) (
90	dr image.Rectangle, mask image.Image, maskp image.Point, advance fixed.Int26_6, ok bool) {
91
92loop:
93	for _, rr := range [2]rune{r, '\ufffd'} {
94		for _, rng := range f.Ranges {
95			if rr < rng.Low || rng.High <= rr {
96				continue
97			}
98			maskp.Y = (int(rr-rng.Low) + rng.Offset) * (f.Ascent + f.Descent)
99			ok = true
100			break loop
101		}
102	}
103	if !ok {
104		return image.Rectangle{}, nil, image.Point{}, 0, false
105	}
106
107	x := int(dot.X+32)>>6 + f.Left
108	y := int(dot.Y+32) >> 6
109	dr = image.Rectangle{
110		Min: image.Point{
111			X: x,
112			Y: y - f.Ascent,
113		},
114		Max: image.Point{
115			X: x + f.Width,
116			Y: y + f.Descent,
117		},
118	}
119
120	return dr, f.Mask, maskp, fixed.I(f.Advance), true
121}
122
123func (f *Face) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) {
124	return fixed.R(0, -f.Ascent, f.Width, +f.Descent), fixed.I(f.Advance), true
125}
126
127func (f *Face) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) {
128	return fixed.I(f.Advance), true
129}
130