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deps,text,widget,font/opentype: [API] add harfbuzz-powered text shaper

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This commit introduces a new text shaping infrastructure
powered by Benoit Kugler's Go source-port of harfbuzz.
This shaper can properly display complex scripts and RTL
text. This commit changes the signature of the text.Shaper
function, which is a breaking API change.

The new functionality is available via opentype.ParseHarfbuzz,
which configures a text.Shaper leveraging the new backend.

References: https://todo.sr.ht/~eliasnaur/gio/146
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
This commit is contained in:
Chris Waldon
2022-03-16 16:01:33 -04:00
committed by Elias Naur
parent db82d12372
commit 1e5a3696f5
12 changed files with 3009 additions and 143 deletions
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text/shaper.go
+32 -12
View File
@@ -3,20 +3,23 @@
package text
import (
"encoding/binary"
"hash/maphash"
"io"
"strings"
"golang.org/x/image/math/fixed"
"gioui.org/io/system"
"gioui.org/op/clip"
)
// Shaper implements layout and shaping of text.
type Shaper interface {
// Layout a text according to a set of options.
Layout(font Font, size fixed.Int26_6, maxWidth int, txt io.Reader) ([]Line, error)
Layout(font Font, size fixed.Int26_6, maxWidth int, lc system.Locale, txt io.RuneReader) ([]Line, error)
// LayoutString is Layout for strings.
LayoutString(font Font, size fixed.Int26_6, maxWidth int, str string) []Line
LayoutString(font Font, size fixed.Int26_6, maxWidth int, lc system.Locale, str string) []Line
// Shape a line of text and return a clipping operation for its outline.
Shape(font Font, size fixed.Int26_6, layout Layout) clip.PathSpec
}
@@ -44,6 +47,7 @@ type faceCache struct {
face Face
layoutCache layoutCache
pathCache pathCache
seed maphash.Seed
}
func (c *Cache) lookup(font Font) *faceCache {
@@ -108,15 +112,15 @@ func NewCache(collection []FontFace) *Cache {
}
// Layout implements the Shaper interface.
func (c *Cache) Layout(font Font, size fixed.Int26_6, maxWidth int, txt io.Reader) ([]Line, error) {
func (c *Cache) Layout(font Font, size fixed.Int26_6, maxWidth int, lc system.Locale, txt io.RuneReader) ([]Line, error) {
cache := c.lookup(font)
return cache.face.Layout(size, maxWidth, txt)
return cache.face.Layout(size, maxWidth, lc, txt)
}
// LayoutString is a caching implementation of the Shaper interface.
func (c *Cache) LayoutString(font Font, size fixed.Int26_6, maxWidth int, str string) []Line {
func (c *Cache) LayoutString(font Font, size fixed.Int26_6, maxWidth int, lc system.Locale, str string) []Line {
cache := c.lookup(font)
return cache.layout(size, maxWidth, str)
return cache.layout(size, maxWidth, lc, str)
}
// Shape is a caching implementation of the Shaper interface. Shape assumes that the layout
@@ -126,7 +130,7 @@ func (c *Cache) Shape(font Font, size fixed.Int26_6, layout Layout) clip.PathSpe
return cache.shape(size, layout)
}
func (f *faceCache) layout(ppem fixed.Int26_6, maxWidth int, str string) []Line {
func (f *faceCache) layout(ppem fixed.Int26_6, maxWidth int, lc system.Locale, str string) []Line {
if f == nil {
return nil
}
@@ -134,27 +138,43 @@ func (f *faceCache) layout(ppem fixed.Int26_6, maxWidth int, str string) []Line
ppem: ppem,
maxWidth: maxWidth,
str: str,
locale: lc,
}
if l, ok := f.layoutCache.Get(lk); ok {
return l
}
l, _ := f.face.Layout(ppem, maxWidth, strings.NewReader(str))
l, _ := f.face.Layout(ppem, maxWidth, lc, strings.NewReader(str))
f.layoutCache.Put(lk, l)
return l
}
// hashGIDs returns a 64-bit hash value of the font GIDs contained
// within the provided layout.
func (f *faceCache) hashGIDs(layout Layout) uint64 {
if f.seed == (maphash.Seed{}) {
f.seed = maphash.MakeSeed()
}
var h maphash.Hash
h.SetSeed(f.seed)
for _, g := range layout.Glyphs {
binary.Write(&h, binary.LittleEndian, g.ID)
}
return h.Sum64()
}
func (f *faceCache) shape(ppem fixed.Int26_6, layout Layout) clip.PathSpec {
if f == nil {
return clip.PathSpec{}
}
pk := pathKey{
ppem: ppem,
str: layout.Text,
ppem: ppem,
str: layout.Text,
gidHash: f.hashGIDs(layout),
}
if clip, ok := f.pathCache.Get(pk); ok {
if clip, ok := f.pathCache.Get(pk, layout); ok {
return clip
}
clip := f.face.Shape(ppem, layout)
f.pathCache.Put(pk, clip)
f.pathCache.Put(pk, layout, clip)
return clip
}