~eliasnaur/gio

ref: 16d2a3ac0a07493f4f3f43beb6b00002a1869f44 gio/font/opentype/opentype.go -rw-r--r-- 6.9 KiB
16d2a3acElias Naur text: remove String, Layout and add Glyph 9 months ago
                                                                                
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
// SPDX-License-Identifier: Unlicense OR MIT

// Package opentype implements text layout and shaping for OpenType
// files.
package opentype

import (
	"io"

	"unicode"
	"unicode/utf8"

	"gioui.org/f32"
	"gioui.org/op"
	"gioui.org/op/clip"
	"gioui.org/text"
	"golang.org/x/image/font"
	"golang.org/x/image/font/sfnt"
	"golang.org/x/image/math/fixed"
)

// Font implements text.Face.
type Font struct {
	font *sfnt.Font
	buf  sfnt.Buffer
}

// Collection is a collection of one or more fonts.
type Collection struct {
	coll *sfnt.Collection
}

type opentype struct {
	Font    *sfnt.Font
	Hinting font.Hinting
}

// NewFont parses an SFNT font, such as TTF or OTF data, from a []byte
// data source.
func Parse(src []byte) (*Font, error) {
	fnt, err := sfnt.Parse(src)
	if err != nil {
		return nil, err
	}
	return &Font{font: fnt}, nil
}

// ParseCollection parses an SFNT font collection, such as TTC or OTC data,
// from a []byte data source.
//
// If passed data for a single font, a TTF or OTF instead of a TTC or OTC,
// it will return a collection containing 1 font.
func ParseCollection(src []byte) (*Collection, error) {
	c, err := sfnt.ParseCollection(src)
	if err != nil {
		return nil, err
	}
	return &Collection{c}, nil
}

// ParseCollectionReaderAt parses an SFNT collection, such as TTC or OTC data,
// from an io.ReaderAt data source.
//
// If passed data for a single font, a TTF or OTF instead of a TTC or OTC, it
// will return a collection containing 1 font.
func ParseCollectionReaderAt(src io.ReaderAt) (*Collection, error) {
	c, err := sfnt.ParseCollectionReaderAt(src)
	if err != nil {
		return nil, err
	}
	return &Collection{c}, nil
}

// NumFonts returns the number of fonts in the collection.
func (c *Collection) NumFonts() int {
	return c.coll.NumFonts()
}

// Font returns the i'th font in the collection.
func (c *Collection) Font(i int) (*Font, error) {
	fnt, err := c.coll.Font(i)
	if err != nil {
		return nil, err
	}
	return &Font{font: fnt}, nil
}

func (f *Font) Layout(ppem fixed.Int26_6, str string, opts text.LayoutOptions) []text.Line {
	return layoutText(&f.buf, ppem, str, &opentype{Font: f.font, Hinting: font.HintingFull}, opts)
}

func (f *Font) Shape(ppem fixed.Int26_6, str []text.Glyph) op.CallOp {
	return textPath(&f.buf, ppem, &opentype{Font: f.font, Hinting: font.HintingFull}, str)
}

func (f *Font) Metrics(ppem fixed.Int26_6) font.Metrics {
	o := &opentype{Font: f.font, Hinting: font.HintingFull}
	return o.Metrics(&f.buf, ppem)
}

func layoutText(buf *sfnt.Buffer, ppem fixed.Int26_6, str string, f *opentype, opts text.LayoutOptions) []text.Line {
	m := f.Metrics(buf, ppem)
	lineTmpl := text.Line{
		Ascent: m.Ascent,
		// m.Height is equal to m.Ascent + m.Descent + linegap.
		// Compute the descent including the linegap.
		Descent: m.Height - m.Ascent,
		Bounds:  f.Bounds(buf, ppem),
	}
	var lines []text.Line
	maxDotX := fixed.I(opts.MaxWidth)
	type state struct {
		r      rune
		layout []text.Glyph
		adv    fixed.Int26_6
		x      fixed.Int26_6
		idx    int
		valid  bool
	}
	var prev, word state
	endLine := func() {
		line := lineTmpl
		line.Layout = prev.layout
		line.Len = prev.idx
		line.Width = prev.x + prev.adv
		line.Bounds.Max.X += prev.x
		lines = append(lines, line)
		str = str[prev.idx:]
		prev = state{}
		word = state{}
	}
	for prev.idx < len(str) {
		c, s := utf8.DecodeRuneInString(str[prev.idx:])
		a, valid := f.GlyphAdvance(buf, ppem, c)
		next := state{
			r:      c,
			layout: prev.layout,
			idx:    prev.idx + s,
			x:      prev.x + prev.adv,
			adv:    a,
			valid:  valid,
		}
		if c == '\n' {
			// The newline is zero width; use the previous
			// character for line measurements.
			prev.layout = append(prev.layout, text.Glyph{Rune: c, Advance: 0})
			prev.idx = next.idx
			endLine()
			continue
		}
		var k fixed.Int26_6
		if prev.valid {
			k = f.Kern(buf, ppem, prev.r, next.r)
		}
		// Break the line if we're out of space.
		if prev.idx > 0 && next.x+next.adv+k > maxDotX {
			// If the line contains no word breaks, break off the last rune.
			if word.idx == 0 {
				word = prev
			}
			next.x -= word.x + word.adv
			next.idx -= word.idx
			next.layout = next.layout[len(word.layout):]
			prev = word
			endLine()
		} else if k != 0 {
			next.layout[len(next.layout)-1].Advance += k
			next.x += k
		}
		next.layout = append(next.layout, text.Glyph{Rune: c, Advance: next.adv})
		if unicode.IsSpace(c) {
			word = next
		}
		prev = next
	}
	endLine()
	return lines
}

func textPath(buf *sfnt.Buffer, ppem fixed.Int26_6, f *opentype, str []text.Glyph) op.CallOp {
	var lastPos f32.Point
	var builder clip.Path
	ops := new(op.Ops)
	var x fixed.Int26_6
	builder.Begin(ops)
	for _, g := range str {
		if !unicode.IsSpace(g.Rune) {
			segs, ok := f.LoadGlyph(buf, ppem, g.Rune)
			if !ok {
				continue
			}
			// Move to glyph position.
			pos := f32.Point{
				X: float32(x) / 64,
			}
			builder.Move(pos.Sub(lastPos))
			lastPos = pos
			var lastArg f32.Point
			// Convert sfnt.Segments to relative segments.
			for _, fseg := range segs {
				nargs := 1
				switch fseg.Op {
				case sfnt.SegmentOpQuadTo:
					nargs = 2
				case sfnt.SegmentOpCubeTo:
					nargs = 3
				}
				var args [3]f32.Point
				for i := 0; i < nargs; i++ {
					a := f32.Point{
						X: float32(fseg.Args[i].X) / 64,
						Y: float32(fseg.Args[i].Y) / 64,
					}
					args[i] = a.Sub(lastArg)
					if i == nargs-1 {
						lastArg = a
					}
				}
				switch fseg.Op {
				case sfnt.SegmentOpMoveTo:
					builder.Move(args[0])
				case sfnt.SegmentOpLineTo:
					builder.Line(args[0])
				case sfnt.SegmentOpQuadTo:
					builder.Quad(args[0], args[1])
				case sfnt.SegmentOpCubeTo:
					builder.Cube(args[0], args[1], args[2])
				default:
					panic("unsupported segment op")
				}
			}
			lastPos = lastPos.Add(lastArg)
		}
		x += g.Advance
	}
	builder.End().Add(ops)
	return op.CallOp{Ops: ops}
}

func (f *opentype) GlyphAdvance(buf *sfnt.Buffer, ppem fixed.Int26_6, r rune) (advance fixed.Int26_6, ok bool) {
	g, err := f.Font.GlyphIndex(buf, r)
	if err != nil {
		return 0, false
	}
	adv, err := f.Font.GlyphAdvance(buf, g, ppem, f.Hinting)
	return adv, err == nil
}

func (f *opentype) Kern(buf *sfnt.Buffer, ppem fixed.Int26_6, r0, r1 rune) fixed.Int26_6 {
	g0, err := f.Font.GlyphIndex(buf, r0)
	if err != nil {
		return 0
	}
	g1, err := f.Font.GlyphIndex(buf, r1)
	if err != nil {
		return 0
	}
	adv, err := f.Font.Kern(buf, g0, g1, ppem, f.Hinting)
	if err != nil {
		return 0
	}
	return adv
}

func (f *opentype) Metrics(buf *sfnt.Buffer, ppem fixed.Int26_6) font.Metrics {
	m, _ := f.Font.Metrics(buf, ppem, f.Hinting)
	return m
}

func (f *opentype) Bounds(buf *sfnt.Buffer, ppem fixed.Int26_6) fixed.Rectangle26_6 {
	r, _ := f.Font.Bounds(buf, ppem, f.Hinting)
	return r
}

func (f *opentype) LoadGlyph(buf *sfnt.Buffer, ppem fixed.Int26_6, r rune) ([]sfnt.Segment, bool) {
	g, err := f.Font.GlyphIndex(buf, r)
	if err != nil {
		return nil, false
	}
	segs, err := f.Font.LoadGlyph(buf, g, ppem, nil)
	if err != nil {
		return nil, false
	}
	return segs, true
}