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[shaping] add support for custom letter and word spacing (#165)
* [shaping] add support for custom letter and word spacing * fix typo in documentation Co-authored-by: Chris Waldon <[email protected]> * do not observe buffer alt slice directly * fix doc typo --------- Co-authored-by: Chris Waldon <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,127 @@ | ||
| package shaping | ||
|
|
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| import ( | ||
| "golang.org/x/image/math/fixed" | ||
| ) | ||
|
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| // AddWordSpacing alters the run, adding [additionalSpacing] on each | ||
| // word separator. | ||
| // [text] is the input slice used to create the run. | ||
| // Note that space is always added, even on boundaries. | ||
| // | ||
| // See also the convenience function [AddSpacing] to handle a slice of runs. | ||
|
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| // See also https://www.w3.org/TR/css-text-3/#word-separator | ||
| func (run *Output) AddWordSpacing(text []rune, additionalSpacing fixed.Int26_6) { | ||
| isVertical := run.Direction.IsVertical() | ||
| for i, g := range run.Glyphs { | ||
| // find the corresponding runes : | ||
| // to simplify, we assume a simple one to one rune/glyph mapping | ||
| // which should be common in practice for word separators | ||
| if !(g.RuneCount == 1 && g.GlyphCount == 1) { | ||
| continue | ||
| } | ||
| r := text[g.ClusterIndex] | ||
| switch r { | ||
| case '\u0020', // space | ||
| '\u00A0', // no-break space | ||
| '\u1361', // Ethiopic word space | ||
| '\U00010100', '\U00010101', // Aegean word separators | ||
| '\U0001039F', // Ugaritic word divider | ||
| '\U0001091F': // Phoenician word separator | ||
| default: | ||
| continue | ||
| } | ||
| // we have a word separator: add space | ||
| // we do it by enlarging the separator glyph advance | ||
| // and distributing space around the glyph content | ||
| if isVertical { | ||
| run.Glyphs[i].YAdvance += additionalSpacing | ||
| run.Glyphs[i].YOffset += additionalSpacing / 2 | ||
| } else { | ||
| run.Glyphs[i].XAdvance += additionalSpacing | ||
| run.Glyphs[i].XOffset += additionalSpacing / 2 | ||
| } | ||
| } | ||
| run.RecomputeAdvance() | ||
| } | ||
|
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| // AddLetterSpacing alters the run, adding [additionalSpacing] between | ||
| // each Harfbuzz clusters. | ||
| // | ||
| // Space is added at the boundaries if and only if there is an adjacent run, as specified by [isStartRun] and [isEndRun]. | ||
| // | ||
| // See also the convenience function [AddSpacing] to handle a slice of runs. | ||
| // | ||
| // See also https://www.w3.org/TR/css-text-3/#letter-spacing-property | ||
| func (run *Output) AddLetterSpacing(additionalSpacing fixed.Int26_6, isStartRun, isEndRun bool) { | ||
| isVertical := run.Direction.IsVertical() | ||
|
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| halfSpacing := additionalSpacing / 2 | ||
| for startGIdx := 0; startGIdx < len(run.Glyphs); { | ||
| startGlyph := run.Glyphs[startGIdx] | ||
| endGIdx := startGIdx + startGlyph.GlyphCount - 1 | ||
|
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| // start : apply spacing at boundary only if the run is not the first | ||
| if startGIdx > 0 || !isStartRun { | ||
| if isVertical { | ||
| run.Glyphs[startGIdx].YAdvance += halfSpacing | ||
| run.Glyphs[startGIdx].YOffset += halfSpacing | ||
| } else { | ||
| run.Glyphs[startGIdx].XAdvance += halfSpacing | ||
| run.Glyphs[startGIdx].XOffset += halfSpacing | ||
| } | ||
| run.Glyphs[startGIdx].startLetterSpacing += halfSpacing | ||
| } | ||
|
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| // end : apply spacing at boundary only if the run is not the last | ||
| isLastCluster := startGIdx+startGlyph.GlyphCount >= len(run.Glyphs) | ||
| if !isLastCluster || !isEndRun { | ||
| if isVertical { | ||
| run.Glyphs[endGIdx].YAdvance += halfSpacing | ||
| } else { | ||
| run.Glyphs[endGIdx].XAdvance += halfSpacing | ||
| } | ||
| run.Glyphs[endGIdx].endLetterSpacing += halfSpacing | ||
| } | ||
|
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||
| // go to next cluster | ||
| startGIdx += startGlyph.GlyphCount | ||
| } | ||
|
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| run.RecomputeAdvance() | ||
| } | ||
|
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| // does not run RecomputeAdvance | ||
| func (run *Output) trimStartLetterSpacing() { | ||
| if len(run.Glyphs) == 0 { | ||
| return | ||
| } | ||
| firstG := &run.Glyphs[0] | ||
| halfSpacing := firstG.startLetterSpacing | ||
| if run.Direction.IsVertical() { | ||
| firstG.YAdvance -= halfSpacing | ||
| firstG.YOffset -= halfSpacing | ||
| } else { | ||
| firstG.XAdvance -= halfSpacing | ||
| firstG.XOffset -= halfSpacing | ||
| } | ||
| firstG.startLetterSpacing = 0 | ||
| } | ||
|
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| // AddSpacing adds additionnal spacing between words and letters, mutating the given [runs]. | ||
| // [text] is the input slice the [runs] refer to. | ||
| // | ||
| // See the method [Output.AddWordSpacing] and [Output.AddLetterSpacing] for details | ||
| // about what spacing actually is. | ||
| func AddSpacing(runs []Output, text []rune, wordSpacing, letterSpacing fixed.Int26_6) { | ||
| for i := range runs { | ||
| isStartRun, isEndRun := i == 0, i == len(runs)-1 | ||
| if wordSpacing != 0 { | ||
| runs[i].AddWordSpacing(text, wordSpacing) | ||
| } | ||
| if letterSpacing != 0 { | ||
| runs[i].AddLetterSpacing(letterSpacing, isStartRun, isEndRun) | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,158 @@ | ||
| package shaping | ||
|
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| import ( | ||
| "testing" | ||
|
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| "github.com/go-text/typesetting/di" | ||
| "github.com/go-text/typesetting/font" | ||
| "github.com/go-text/typesetting/language" | ||
| tu "github.com/go-text/typesetting/testutils" | ||
| "golang.org/x/image/math/fixed" | ||
| ) | ||
|
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||
| func simpleShape(text []rune, face *font.Face, dir di.Direction) Output { | ||
| input := Input{ | ||
| Text: text, | ||
| RunStart: 0, | ||
| RunEnd: len(text), | ||
| Direction: dir, | ||
| Face: face, | ||
| Size: 16 * 72 * 10, | ||
| Script: language.LookupScript(text[0]), | ||
| } | ||
| return (&HarfbuzzShaper{}).Shape(input) | ||
| } | ||
|
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| func TestOutput_addWordSpacing(t *testing.T) { | ||
| latinFont := loadOpentypeFont(t, "../font/testdata/Roboto-Regular.ttf") | ||
| arabicFont := loadOpentypeFont(t, "../font/testdata/Amiri-Regular.ttf") | ||
| english := []rune("\U0001039FHello\u1361world ! : the\u00A0end") | ||
| arabic := []rune("تثذرزسشص لمنهويء") | ||
|
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| addSpacing := fixed.I(20) | ||
| out := simpleShape(english, latinFont, di.DirectionLTR) | ||
| withoutSpacing := out.Advance | ||
| out.AddWordSpacing(english, addSpacing) | ||
| tu.Assert(t, out.Advance == withoutSpacing+6*addSpacing) | ||
|
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| out = simpleShape(arabic, arabicFont, di.DirectionRTL) | ||
| withoutSpacing = out.Advance | ||
| out.AddWordSpacing(arabic, addSpacing) | ||
| tu.Assert(t, out.Advance == withoutSpacing+1*addSpacing) | ||
|
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| // vertical | ||
| out = simpleShape(english, latinFont, di.DirectionTTB) | ||
| withoutSpacing = out.Advance | ||
| out.AddWordSpacing(english, addSpacing) | ||
| tu.Assert(t, out.Advance == withoutSpacing+6*addSpacing) | ||
| } | ||
|
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| func TestOutput_addLetterSpacing(t *testing.T) { | ||
| latinFont := loadOpentypeFont(t, "../font/testdata/Roboto-Regular.ttf") | ||
| arabicFont := loadOpentypeFont(t, "../font/testdata/Amiri-Regular.ttf") | ||
| english := []rune("Hello world ! : the end") | ||
| englishWithLigature := []rune("Hello final") | ||
| arabic := []rune("تثذرزسشص لمنهويء") | ||
|
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| addSpacing := fixed.I(4) | ||
| halfSpacing := addSpacing / 2 | ||
| for _, test := range []struct { | ||
| text []rune | ||
| face *font.Face | ||
| dir di.Direction | ||
| start, end bool | ||
| expectedBonusAdvance fixed.Int26_6 | ||
| }{ | ||
| // LTR | ||
| {english, latinFont, di.DirectionLTR, false, false, 23 * addSpacing}, | ||
| {english, latinFont, di.DirectionLTR, true, true, 22 * addSpacing}, | ||
| {english, latinFont, di.DirectionLTR, true, false, 22*addSpacing + halfSpacing}, | ||
| {english, latinFont, di.DirectionLTR, false, true, 22*addSpacing + halfSpacing}, | ||
| {englishWithLigature, latinFont, di.DirectionLTR, true, true, 9 * addSpacing}, // not 10 | ||
| // RTL | ||
| {arabic, arabicFont, di.DirectionRTL, false, false, 16 * addSpacing}, | ||
| {arabic, arabicFont, di.DirectionRTL, true, true, 15 * addSpacing}, | ||
| {arabic, arabicFont, di.DirectionRTL, true, false, 15*addSpacing + halfSpacing}, | ||
| {arabic, arabicFont, di.DirectionRTL, false, true, 15*addSpacing + halfSpacing}, | ||
| // vertical | ||
| {english, latinFont, di.DirectionTTB, false, false, 23 * addSpacing}, | ||
| {english, latinFont, di.DirectionTTB, true, true, 22 * addSpacing}, | ||
| {english, latinFont, di.DirectionTTB, true, false, 22*addSpacing + halfSpacing}, | ||
| {english, latinFont, di.DirectionTTB, false, true, 22*addSpacing + halfSpacing}, | ||
| } { | ||
| out := simpleShape(test.text, test.face, test.dir) | ||
| withoutSpacing := out.Advance | ||
| out.AddLetterSpacing(addSpacing, test.start, test.end) | ||
| tu.Assert(t, out.Advance == withoutSpacing+test.expectedBonusAdvance) | ||
| } | ||
| } | ||
|
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| func TestCustomSpacing(t *testing.T) { | ||
| latinFont := loadOpentypeFont(t, "../font/testdata/Roboto-Regular.ttf") | ||
| english := []rune("Hello world ! : the end") | ||
|
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| letterSpacing, wordSpacing := fixed.I(4), fixed.I(20) | ||
| out := simpleShape(english, latinFont, di.DirectionLTR) | ||
| withoutSpacing := out.Advance | ||
| out.AddWordSpacing(english, wordSpacing) | ||
| out.AddLetterSpacing(letterSpacing, false, false) | ||
| tu.Assert(t, out.Advance == withoutSpacing+5*wordSpacing+23*letterSpacing) | ||
| } | ||
|
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| // make sure that additional letter spacing is properly removed | ||
| // at the start and end of wrapped lines | ||
| func TestTrailingSpaces(t *testing.T) { | ||
| letterSpacing, charAdvance := fixed.I(8), fixed.I(90) | ||
| halfSpacing := letterSpacing / 2 | ||
| monoFont := loadOpentypeFont(t, "../font/testdata/UbuntuMono-R.ttf") | ||
|
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| text := []rune("Hello world ! : the end_") | ||
|
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| out := simpleShape(text, monoFont, di.DirectionLTR) | ||
| tu.Assert(t, out.Advance == fixed.Int26_6(len(text))*charAdvance) // assume 1:1 rune glyph mapping | ||
|
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| type test struct { | ||
| toWrap []Output | ||
| policy LineBreakPolicy | ||
| width int | ||
| expectedRuns [][][2]fixed.Int26_6 // first and last advance, for each line and each run | ||
| } | ||
|
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| for _, test := range []test{ | ||
| { // from one run | ||
| []Output{out.copy()}, | ||
| 0, 1800, | ||
| [][][2]fixed.Int26_6{ | ||
| {{charAdvance + halfSpacing, 0}}, // line 1 | ||
| {{charAdvance + halfSpacing, charAdvance + halfSpacing}}, // line 2 | ||
| }, | ||
| }, | ||
| { // from two runs, break between | ||
| cutRunInto(out.copy(), 2), Always, 1172, // end of the first run | ||
| [][][2]fixed.Int26_6{ | ||
| {{charAdvance + halfSpacing, 0}}, // line 1 | ||
| {{charAdvance + halfSpacing, charAdvance + halfSpacing}}, // line 2 | ||
| }, | ||
| }, | ||
| { // from two runs, break inside | ||
| cutRunInto(out.copy(), 2), 0, 1800, | ||
| [][][2]fixed.Int26_6{ | ||
| {{charAdvance + halfSpacing, charAdvance + letterSpacing}, {charAdvance + letterSpacing, 0}}, // line 1 | ||
| {{charAdvance + halfSpacing, charAdvance + halfSpacing}}, // line 2 | ||
| }, | ||
| }, | ||
| } { | ||
| AddSpacing(test.toWrap, text, 0, letterSpacing) | ||
| lines, _ := (&LineWrapper{}).WrapParagraph(WrapConfig{BreakPolicy: test.policy}, test.width, text, NewSliceIterator(test.toWrap)) | ||
| tu.Assert(t, len(lines) == len(test.expectedRuns)) | ||
| for i, expLine := range test.expectedRuns { | ||
| gotLine := lines[i] | ||
| tu.Assert(t, len(gotLine) == len(expLine)) | ||
| for j, run := range expLine { | ||
| gotRun := gotLine[j] | ||
| tu.Assert(t, gotRun.Glyphs[0].XAdvance == run[0]) | ||
| tu.Assert(t, gotRun.Glyphs[len(gotRun.Glyphs)-1].XAdvance == run[1]) | ||
| } | ||
| } | ||
| } | ||
| } |
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