mirror of
https://github.com/zoriya/react-native-svg.git
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Use setFontFeatureSettings for disabling all discretionary ligatures while keeping required ligatures (e.g. in Arabic)
This commit is contained in:
Mikael Sand
@@ -19,6 +19,7 @@ import android.graphics.PathMeasure;
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import android.graphics.Rect;
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import android.graphics.RectF;
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import android.graphics.Typeface;
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import android.os.Build;
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import android.support.v4.graphics.PaintCompat;
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import com.facebook.react.bridge.ReadableMap;
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@@ -117,6 +118,122 @@ class TSpanShadowNode extends TextShadowNode {
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GlyphPathBag bag = new GlyphPathBag(paint);
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boolean[] ligature = new boolean[length];
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final char[] chars = line.toCharArray();
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/*
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*
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* Three properties affect the space between characters and words:
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*
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* ‘kerning’ indicates whether the user agent should adjust inter-glyph spacing
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* based on kerning tables that are included in the relevant font
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* (i.e., enable auto-kerning) or instead disable auto-kerning
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* and instead set inter-character spacing to a specific length (typically, zero).
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*
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* ‘letter-spacing’ indicates an amount of space that is to be added between text
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* characters supplemental to any spacing due to the ‘kerning’ property.
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*
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* ‘word-spacing’ indicates the spacing behavior between words.
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*
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* Letter-spacing is applied after bidi reordering and is in addition to any word-spacing.
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* Depending on the justification rules in effect, user agents may further increase
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* or decrease the space between typographic character units in order to justify text.
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*
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* */
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double kerning = font.kerning;
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double wordSpacing = font.wordSpacing;
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double letterSpacing = font.letterSpacing;
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final boolean autoKerning = !font.manualKerning;
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/*
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11.1.2. Fonts and glyphs
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A font consists of a collection of glyphs together with other information (collectively,
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the font tables) necessary to use those glyphs to present characters on some visual medium.
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The combination of the collection of glyphs and the font tables is called the font data.
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A font may supply substitution and positioning tables that can be used by a formatter
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(text shaper) to re-order, combine and position a sequence of glyphs to form one or more
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composite glyphs.
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The combining may be as simple as a ligature, or as complex as an indic syllable which
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combines, usually with some re-ordering, multiple consonants and vowel glyphs.
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The tables may be language dependent, allowing the use of language appropriate letter forms.
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When a glyph, simple or composite, represents an indivisible unit for typesetting purposes,
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it is know as a typographic character.
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Ligatures are an important feature of advance text layout. Some ligatures are discretionary
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while others (e.g. in Arabic) are required.
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The following explicit rules apply to ligature formation:
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Ligature formation should not be enabled when characters are in different DOM text nodes;
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thus, characters separated by markup should not use ligatures.
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Ligature formation should not be enabled when characters are in different text chunks.
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Discretionary ligatures should not be used when the spacing between two characters is not
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the same as the default space (e.g. when letter-spacing has a non-default value,
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or text-align has a value of justify and text-justify has a value of distribute).
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(See CSS Text Module Level 3, ([css-text-3]).
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SVG attributes such as ‘dx’, ‘textLength’, and ‘spacing’ (in ‘textPath’) that may reposition
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typographic characters do not break discretionary ligatures.
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If discretionary ligatures are not desired
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they can be turned off by using the font-variant-ligatures property.
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/*
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When the effective letter-spacing between two characters is not zero
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(due to either justification or non-zero computed ‘letter-spacing’),
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user agents should not apply optional ligatures.
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https://www.w3.org/TR/css-text-3/#letter-spacing-property
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*/
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final boolean allowOptionalLigatures = letterSpacing == 0 &&
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font.fontVariantLigatures == FontVariantLigatures.normal;
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/*
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For OpenType fonts, discretionary ligatures include those enabled by
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the liga, clig, dlig, hlig, and cala features;
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required ligatures are found in the rlig feature.
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https://svgwg.org/svg2-draft/text.html#FontsGlyphs
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http://dev.w3.org/csswg/css-fonts/#propdef-font-feature-settings
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https://www.microsoft.com/typography/otspec/featurelist.htm
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https://www.microsoft.com/typography/otspec/featuretags.htm
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https://www.microsoft.com/typography/otspec/features_pt.htm
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https://www.microsoft.com/typography/otfntdev/arabicot/features.aspx
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http://unifraktur.sourceforge.net/testcases/enable_opentype_features/
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https://en.wikipedia.org/wiki/List_of_typographic_features
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http://ilovetypography.com/OpenType/opentype-features.html
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https://www.typotheque.com/articles/opentype_features_in_css
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https://practice.typekit.com/lesson/caring-about-opentype-features/
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http://stateofwebtype.com/
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6.12. Low-level font feature settings control: the font-feature-settings property
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Name: font-feature-settings
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Value: normal | <feature-tag-value> #
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Initial: normal
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Applies to: all elements
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Inherited: yes
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Percentages: N/A
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Media: visual
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Computed value: as specified
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Animatable: no
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*/
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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
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if (allowOptionalLigatures) {
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paint.setFontFeatureSettings("'kern', 'liga', 'clig', 'dlig', 'hlig', 'cala', 'rlig'");
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} else {
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paint.setFontFeatureSettings("'kern', 'liga' 0, 'clig' 0, 'dlig' 0, 'hlig' 0, 'cala' 0, 'rlig'");
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}
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}
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// OpenType.js font data
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ReadableMap fontData = font.fontData;
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float[] advances = new float[length];
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paint.getTextWidths(line, advances);
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@@ -266,90 +383,6 @@ class TSpanShadowNode extends TextShadowNode {
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TODO implement stretch
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*/
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/*
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*
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* Three properties affect the space between characters and words:
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*
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* ‘kerning’ indicates whether the user agent should adjust inter-glyph spacing
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* based on kerning tables that are included in the relevant font
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* (i.e., enable auto-kerning) or instead disable auto-kerning
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* and instead set inter-character spacing to a specific length (typically, zero).
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*
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* ‘letter-spacing’ indicates an amount of space that is to be added between text
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* characters supplemental to any spacing due to the ‘kerning’ property.
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*
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* ‘word-spacing’ indicates the spacing behavior between words.
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*
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* Letter-spacing is applied after bidi reordering and is in addition to any word-spacing.
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* Depending on the justification rules in effect, user agents may further increase
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* or decrease the space between typographic character units in order to justify text.
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*
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* */
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double kerning = font.kerning;
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double wordSpacing = font.wordSpacing;
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double letterSpacing = font.letterSpacing;
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final boolean autoKerning = !font.manualKerning;
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/*
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11.1.2. Fonts and glyphs
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A font consists of a collection of glyphs together with other information (collectively,
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the font tables) necessary to use those glyphs to present characters on some visual medium.
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The combination of the collection of glyphs and the font tables is called the font data.
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A font may supply substitution and positioning tables that can be used by a formatter
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(text shaper) to re-order, combine and position a sequence of glyphs to form one or more
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composite glyphs.
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The combining may be as simple as a ligature, or as complex as an indic syllable which
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combines, usually with some re-ordering, multiple consonants and vowel glyphs.
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The tables may be language dependent, allowing the use of language appropriate letter forms.
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When a glyph, simple or composite, represents an indivisible unit for typesetting purposes,
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it is know as a typographic character.
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Ligatures are an important feature of advance text layout. Some ligatures are discretionary
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(TODO) while others (e.g. in Arabic) are required.
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The following explicit rules apply to ligature formation:
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Ligature formation should not be enabled when characters are in different DOM text nodes;
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thus, characters separated by markup should not use ligatures.
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Ligature formation should not be enabled when characters are in different text chunks.
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Discretionary ligatures should not be used when the spacing between two characters is not
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the same as the default space (e.g. when letter-spacing has a non-default value,
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or text-align has a value of justify and text-justify has a value of distribute).
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(See CSS Text Module Level 3, ([css-text-3]).
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SVG attributes such as ‘dx’, ‘textLength’, and ‘spacing’ (in ‘textPath’) that may reposition
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typographic characters do not break discretionary ligatures.
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If discretionary ligatures are not desired
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they can be turned off by using the font-variant-ligatures property.
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/*
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When the effective letter-spacing between two characters is not zero
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(due to either justification or non-zero computed ‘letter-spacing’),
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user agents should not apply optional ligatures.
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https://www.w3.org/TR/css-text-3/#letter-spacing-property
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*/
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final boolean allowOptionalLigatures = letterSpacing == 0 &&
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font.fontVariantLigatures == FontVariantLigatures.normal;
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/*
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For OpenType fonts, discretionary ligatures include those enabled by
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the liga, clig, dlig, hlig, and cala features;
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TODO required ligatures are found in the rlig feature.
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https://svgwg.org/svg2-draft/text.html#FontsGlyphs
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*/
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// OpenType.js font data
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ReadableMap fontData = font.fontData;
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/*
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Name Value Initial value Animatable
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textLength <length> | <percentage> | <number> See below yes
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