* \[Experimental\] Add a font feature for texture control (#2081).

- Currently only available through custom builds with `build-texture-feature = true`.

changes/27.3.5.md

@@ -3,3 +3,5 @@
 * Fix serifs of GREEK LETTER DIGAMMA (`U+03DC`) under `ss12`.
 * Improve crossbar position of GREEK SMALL LETTER DIGAMMA (`U+03DD`) and add a middle serif under slab.
 * Refine Greek Capital Sho (U+03F7) glyph (#2079).
+* \[Experimental\] Add a font feature for texture control (#2081).
+  - Currently only available through custom builds with `build-texture-feature = true`.

font-src/glyphs/auto-build/transformed.ptl

@@ -3,7 +3,7 @@ $$include '../../meta/macros.ptl'
 
 import [linreg clamp mix fallback] from"../../support/utils.mjs"
 import [getGrTree IsSuperscript IsSubscript] from"../../support/gr.mjs"
-import [AnyCv DotlessOrNot CvDecompose MathSansSerif] from"../../support/gr.mjs"
+import [AnyCv DotlessOrNot CvDecompose MathSansSerif Texture] from"../../support/gr.mjs"
 import [NumeratorForm DenominatorForm] from"../../support/gr.mjs"
 import [Transform] from"../../support/geometry/transform.mjs"
 extern Map
@@ -693,6 +693,68 @@ glyph-block Autobuild-Transformed : begin
 
 		link-relations relSets
 
+glyph-block Autobuild-Transformed-Texture : begin
+	if (!(para.buildTexture && !para.isQuasiProportional)) : return nothing
+
+	glyph-block-import CommonShapes
+	glyph-block-import Common-Derivatives
+	glyph-block-import Recursive-Build : Fork
+	glyph-block-import Autobuild-Transformed-Shared : extendRelatedGlyphs link-relations wrapName
+
+	define [createTextureDerivatives gr extL extR _records] : begin
+		local { records relSets targetNameMap } : extendRelatedGlyphs gr.key _records
+		local pendingGlyphs : records.map : [record] => record.1
+
+		local forkedPara : Object.assign {.} para
+		if (extL + extR > 0)
+		: then : forkedPara.diversityM = 1 + extL + extR
+		: else : begin
+			forkedPara.diversityF  = 1 + extL + extR
+			forkedPara.diversityI  = 1 + extL + extR
+			forkedPara.diversityII = 1 + extL + extR
+
+		local forked : Fork pendingGlyphs forkedPara
+		foreach {unicode glyphid} [items-of records] : begin
+			if [not : query-glyph targetNameMap.(glyphid)] : begin
+				define glyphT : forked.queryByName glyphid
+				define glyphO : glyphStore.queryByName glyphid
+				if (glyphT && glyphO) : begin
+					if (glyphT.advanceWidth != glyphO.advanceWidth) : begin
+						gr.set glyphO targetNameMap.(glyphid)
+					create-glyph targetNameMap.(glyphid) unicode : glyph-proc
+						include glyphT AS_BASE ALSO_METRICS
+						set-width Width
+						if extL : currentGlyph.applyTransform [Translate (-extL * Width) 0] true
+
+		link-relations relSets
+
+	define ranges : list
+		list 0x41 0x5A
+		list 0x61 0x7A
+		list 0xC0 0xFF
+		list 0x100 0x2AF
+		list 0x370 0x3FF
+		list 0x400 0x4FF
+		list 0x500 0x52F
+
+	define [jobs base] : list
+		local results {}
+		foreach {low high} [items-of ranges] : begin
+			foreach lch [range low till high] : begin
+				local source : glyphStore.queryNameByUnicode lch
+				if source : results.push { null source }
+		return results
+
+	define EXTENSION :  1 / 12
+	define SHRINK    : -1 / 12
+	createTextureDerivatives Texture.ExtL  EXTENSION 0         [jobs 0xF000]
+	createTextureDerivatives Texture.ExtR  0         EXTENSION [jobs 0xF100]
+	createTextureDerivatives Texture.ExtLR EXTENSION EXTENSION [jobs 0xF200]
+	createTextureDerivatives Texture.ShrL  SHRINK    0         [jobs 0xF300]
+	createTextureDerivatives Texture.ShrR  0         SHRINK    [jobs 0xF400]
+	createTextureDerivatives Texture.ShrLR SHRINK    SHRINK    [jobs 0xF500]
+
+
 glyph-block Autobuild-Transformed-Mathematical : begin
 	glyph-block-import CommonShapes
 	glyph-block-import Common-Derivatives

font-src/otl/gsub-cv-ss.ptl

@@ -137,4 +137,6 @@ export : define [buildCVSS gsub para glyphStore] : begin
 
 	gsub.endBlock rec
 
+	return cvs
+
 define [objectIsNotEmpty obj] : obj && [Object.keys obj].length

font-src/otl/gsub-texture.ptl

@@ -0,0 +1,88 @@
+$$include '../meta/macros.ptl'
+
+extern Set
+
+import [Texture CvDecompose] from"../support/gr.mjs"
+
+# Name-driven feature pairs
+export : define [buildGsubTexture gsub glyphStore markGlyphs cvs] : begin
+	local anyMark : Array.from markGlyphs.all
+	local rec : gsub.beginBlock
+
+	define txtr : gsub.addCommonFeature : gsub.createFeature 'TXTR'
+	define { chain-rule reverse-rule } : gsub.ChainRuleBuilder
+
+	local extRFrom { }
+	local extRTo   { }
+	local extLFrom { }
+	local extLTo   { }
+	local shrLFrom { }
+	local shrLTo   { }
+	local shrRFrom { }
+	local shrRTo   { }
+
+	local anyInfluence : new Set
+
+	foreach { gid g } [glyphStore.namedEntries] : if (gid.(0) !== ".") : begin
+		local extL : Texture.ExtL.get g
+		local extR : Texture.ExtR.get g
+		local extLR : Texture.ExtLR.get g
+		local shrL : Texture.ShrL.get g
+		local shrR : Texture.ShrR.get g
+		local shrLR : Texture.ShrLR.get g
+
+		if extR : begin [extRFrom.push gid] [extRTo.push extR]
+		if extL : begin [extLFrom.push gid] [extLTo.push extL]
+		if (extR && extLR) : begin [extLFrom.push extR] [extLTo.push extLR]
+
+		if shrL : begin [shrLFrom.push gid] [shrLTo.push shrL]
+		if shrR : begin [shrRFrom.push gid] [shrRTo.push shrR]
+		if (shrL && shrLR) : begin [shrRFrom.push shrL] [shrRTo.push shrLR]
+
+		if (extL || extR || shrL || shrR) : anyInfluence.add gid
+
+	define subExtR : gsub.createLookup
+		.type 'gsub_chaining'
+		.ignoreGlyphs anyMark
+		.rules : list
+			chain-rule
+				extRFrom ~> extRTo
+				shrLFrom ~> shrLTo
+
+	define subExtL : gsub.createLookup
+		.type 'gsub_chaining'
+		.ignoreGlyphs anyMark
+		.rules : list
+			chain-rule
+				shrRFrom ~> shrRTo
+				extLFrom ~> extLTo
+
+	txtr.addLookup subExtR
+	txtr.addLookup subExtL
+	gsub.setDependency subExtR subExtL
+
+	# Decompose everything if we enable TXTR
+	if cvs
+	: then : begin
+		# Reuse existing Cvdecompose data
+		foreach cv [cvs.values] : begin
+			if cv.decompositionLookup : begin
+				txtr.addLookup cv.decompositionLookup
+				gsub.setDependency cv.decompositionLookup subExtR
+	: else : begin
+		# Built it from scratch
+		local decompose : gsub.createLookup
+			.type 'gsub_multiple'
+			.substitutions {.}
+
+		foreach { gn glyph } [glyphStore.namedEntries] : begin
+			local parts : CvDecompose.get glyph
+			if parts : begin
+				local influenced : anyInfluence.has gn
+				foreach part [items-of parts] : if [anyInfluence.has part] : set influenced true
+				if influenced : set decompose.substitutions.(gn) parts
+
+		txtr.addLookup decompose
+		gsub.setDependency decompose subExtR
+
+	gsub.endBlock rec

font-src/otl/index.ptl

@@ -10,6 +10,7 @@ import [buildFrac] from"./gsub-frac.mjs"
 import [buildCVSS] from"./gsub-cv-ss.mjs"
 import [buildLOCL] from"./gsub-locl.mjs"
 import [buildGsubThousands] from"./gsub-thousands.mjs"
+import [buildGsubTexture] from"./gsub-texture.mjs"
 import [buildMarkMkmk] from"./gpos-mark-mkmk.mjs"
 
 define GDEF_SIMPLE 1
@@ -60,8 +61,9 @@ define [buildGSUB para glyphStore markGlyphs] : begin
 	buildGsubThousands gsub para glyphStore
 
 	# cv##, ss##
+	local cvs nothing
 	if para.enableCvSs : begin
-		buildCVSS gsub para glyphStore
+		set cvs : buildCVSS gsub para glyphStore
 
 	# ccmp post cv/ss (for Ogonek shape transform)
 	buildCCMPPostCvSs gsub ccmp glyphStore markGlyphs
@@ -70,6 +72,10 @@ define [buildGSUB para glyphStore markGlyphs] : begin
 	# Builds last, but the lookups are added into the beginning of the lookup list
 	buildLOCL gsub para glyphStore
 
+	# TXTR, "texture" feature
+	if (para.buildTexture && !para.isQuasiProportional) : begin
+		 buildGsubTexture gsub glyphStore markGlyphs cvs
+
 	gsub.finalize
 	return gsub
 

font-src/support/gr.mjs

@@ -23,8 +23,19 @@ export const VS01 = LinkedGlyphProp("VS01");
 export const TieMark = LinkedGlyphProp("TieMark");
 export const LeaningMark = LinkedGlyphProp("LeaningMark");
 export const LeaningMarkSpacer = LinkedGlyphProp("LeaningMarkSpacer");
+
+export const Texture = {
+	ExtL: LinkedGlyphProp("TextureExtL"),
+	ExtR: LinkedGlyphProp("TextureExtR"),
+	ExtLR: LinkedGlyphProp("TextureExtLR"),
+	ShrL: LinkedGlyphProp("TextureShrL"),
+	ShrR: LinkedGlyphProp("TextureShrR"),
+	ShrLR: LinkedGlyphProp("TextureShrLR")
+};
+
 function LinkedGlyphProp(key) {
 	return {
+		key,
 		get(glyph) {
 			if (glyph && glyph.related) return glyph.related[key];
 			else return null;

font-src/support/parameters.mjs

@@ -11,6 +11,7 @@ export function init(data, argv) {
 	applyAlternatesParam(argv, para, data, "slope", "slope");
 	if (argv.featureControl.noCvSs) para.enableCvSs = false;
 	if (argv.featureControl.noLigation) para.enableLigation = false;
+	if (argv.featureControl.buildTexture) para.buildTexture = true;
 	return para;
 }
 function applyBlendingParam(argv, para, data, key, keyArgv) {

utility/export-data/coverage-export/block-data.mjs

@@ -3,7 +3,8 @@ import UnicodeDataIndex from "@unicode/unicode-15.0.0";
 export async function collectBlockData() {
 	const BlockData = [
 		[[0xe0a0, 0xe0df], "Private Use Area — Powerline"],
-		[[0xee00, 0xee3f], "Private Use Area — Progress Bar"]
+		[[0xee00, 0xee3f], "Private Use Area — Progress Bar"],
+		[[0xf000, 0xf8ff], "Private Use Area — Texture"]
 	];
 
 	for (const id of UnicodeDataIndex.Block) {

verdafile.mjs

@@ -230,6 +230,7 @@ const CompositesFromBuildPlan = computed(`metadata:composites-from-build-plan`,
 	return data;
 });
 
+// eslint-disable-next-line complexity
 const FontInfoOf = computed.group("metadata:font-info-of", async (target, fileName) => {
 	const [{ fileNameToBpMap, buildPlans }] = await target.need(BuildPlans);
 	const [version] = await target.need(Version);
@@ -261,7 +262,8 @@ const FontInfoOf = computed.group("metadata:font-info-of", async (target, fileNa
 		featureControl: {
 			noCvSs: bp["no-cv-ss"] || false,
 			noLigation: bp["no-ligation"] || false,
-			exportGlyphNames: bp["export-glyph-names"] || false
+			exportGlyphNames: bp["export-glyph-names"] || false,
+			buildTexture: bp["build-texture-feature"] || false
 		},
 		// Ligations
 		ligations: bp.ligations || null,