Add support for OpenType frac feature (#1230).

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

@@ -2,7 +2,9 @@
 $$include '../../meta/macros.ptl'
 
 import [linreg clamp mix fallback] from '../../support/utils'
-import [AnyCv DotlessOrNot getGrTree getGrMesh CvDecompose MathSansSerif] from "../../support/gr"
+import [getGrTree getGrMesh] from "../../support/gr"
+import [AnyCv DotlessOrNot CvDecompose MathSansSerif] from "../../support/gr"
+import [NumeratorForm DenominatorForm] from "../../support/gr"
 extern Map
 extern Set
 
@@ -50,6 +52,7 @@ glyph-block Autobuild-Transformed-Shared : begin
 				local relatedRecord : record.slice 0
 				set relatedRecord.0 null
 				set relatedRecord.1 relSrcName
+				set relatedRecord.2 true
 				relatedRecords.push relatedRecord
 
 				relSets.push { gr origDstName relDstName }
@@ -74,16 +77,16 @@ glyph-block Autobuild-Transformed : begin
 	glyph-block-import Mark-Below : belowMarkBot belowMarkTop
 	glyph-block-import Autobuild-Transformed-Shared : extendRelatedGlyphs link-relations
 
-	define [createSuperscripts _records] : begin
-		local {records relSets targetNameMap} : extendRelatedGlyphs 'sup' _records
+	define [createSuperscripts prefix gr _records] : begin
+		local {records relSets targetNameMap} : extendRelatedGlyphs prefix _records
 		local pendingGlyphs : records.map : [record] => record.1
 		local miniatureFont : Miniature pendingGlyphs
 			crowd  -- 3.5
 			scale  -- 0.7
 			mono   -- true
-			sbscale -- 1
-		foreach {unicode glyphid} [items-of records]
-			if [not : query-glyph targetNameMap.(glyphid)]
+			sbscale -- 0.75
+		foreach { unicode glyphid fRelated } [items-of records]
+			if [not : query-glyph targetNameMap.(glyphid)] : begin
 				create-glyph (targetNameMap.(glyphid)) unicode : glyph-proc
 					if [not : miniatureFont.queryByName glyphid] : begin
 						throw : new Error "Cannot find glyph \(glyphid)"
@@ -94,19 +97,20 @@ glyph-block Autobuild-Transformed : begin
 					include [Scale 0.7] true
 					include [Translate middle (CAP + AccentStackOffset / 2)] true
 					include [Italify] true
+				if ([not fRelated] && gr) : gr.set [query-glyph glyphid] (targetNameMap.(glyphid))
 		link-relations relSets
 		return { targetNameMap records }
 
-	define [createSubscripts _records] : begin
-		local {records relSets targetNameMap} : extendRelatedGlyphs 'sub' _records
+	define [createSubscripts prefix gr _records] : begin
+		local {records relSets targetNameMap} : extendRelatedGlyphs prefix _records
 		local pendingGlyphs : records.map : [record] => record.1
 		local miniatureFont : Miniature pendingGlyphs
 			crowd  -- 3.5
 			scale  -- 0.7
 			mono   -- true
-			sbscale -- 1
-		foreach {unicode glyphid} [items-of records]
-			if [not : query-glyph targetNameMap.(glyphid)]
+			sbscale -- 0.75
+		foreach { unicode glyphid fRelated } [items-of records]
+			if [not : query-glyph targetNameMap.(glyphid)] : begin
 				create-glyph (targetNameMap.(glyphid)) unicode : glyph-proc
 					local middle : [miniatureFont.queryByName glyphid].advanceWidth / 2
 					include [miniatureFont.queryByName glyphid] AS_BASE ALSO_METRICS
@@ -115,6 +119,7 @@ glyph-block Autobuild-Transformed : begin
 					include [Scale 0.7] true
 					include [Translate middle (Descender / 2)] true
 					include [Italify] true
+				if ([not fRelated] && gr) : gr.set [query-glyph glyphid] (targetNameMap.(glyphid))
 		link-relations relSets
 
 	# Not used today -- may be used in the future
@@ -191,7 +196,7 @@ glyph-block Autobuild-Transformed : begin
 
 		link-relations relSets
 
-	createSuperscripts : list
+	createSuperscripts 'sup' null : list
 		list 0x00AA 'aSbRsbUnderlineBelow'
 		list 0x00BA 'oSbRsbUnderlineBelow'
 		list 0x2070 'zero.lnum'
@@ -322,15 +327,37 @@ glyph-block Autobuild-Transformed : begin
 		list 0xA7F8 'smcpHbar'
 		list 0xA7F9 'oe'
 
+	createSuperscripts 'numerator' NumeratorForm : list
+		list null 'zero.onum'
+		list null 'one.onum'
+		list null 'two.onum'
+		list null 'three.onum'
+		list null 'four.onum'
+		list null 'five.onum'
+		list null 'six.onum'
+		list null 'seven.onum'
+		list null 'eight.onum'
+		list null 'nine.onum'
+		list null 'zero.lnum'
+		list null 'one.lnum'
+		list null 'two.lnum'
+		list null 'three.lnum'
+		list null 'four.lnum'
+		list null 'five.lnum'
+		list null 'six.lnum'
+		list null 'seven.lnum'
+		list null 'eight.lnum'
+		list null 'nine.lnum'
+
 	do "superscript AE"
-		define { tnmAHalf jobsAHalf } : createSuperscripts { { null 'AE/AHalf' } }
-		define { tnmEHalf jobsEHalf } : createSuperscripts { { null 'AE/EHalf' } }
+		define { tnmAHalf jobsAHalf } : createSuperscripts 'sup' null { { null 'AE/AHalf' } }
+		define { tnmEHalf jobsEHalf } : createSuperscripts 'sup' null { { null 'AE/EHalf' } }
 		create-glyph 'sup{AE}' 0x1D2D : glyph-proc
 			include [refer-glyph tnmAHalf.('AE/AHalf')] AS_BASE ALSO_METRICS
 			include [refer-glyph tnmEHalf.('AE/EHalf')]
 			CvDecompose.set currentGlyph { tnmAHalf.('AE/AHalf') tnmEHalf.('AE/EHalf') }
 
-	createSubscripts : list
+	createSubscripts 'sub' null : list
 		list 0x2080 'zero.lnum'
 		list 0x2081 'one.lnum'
 		list 0x2082 'two.lnum'
@@ -370,6 +397,28 @@ glyph-block Autobuild-Transformed : begin
 		list 0x208D 'parenLeft'
 		list 0x208E 'parenRight'
 
+	createSubscripts 'denominator' DenominatorForm : list
+		list null 'zero.onum'
+		list null 'one.onum'
+		list null 'two.onum'
+		list null 'three.onum'
+		list null 'four.onum'
+		list null 'five.onum'
+		list null 'six.onum'
+		list null 'seven.onum'
+		list null 'eight.onum'
+		list null 'nine.onum'
+		list null 'zero.lnum'
+		list null 'one.lnum'
+		list null 'two.lnum'
+		list null 'three.lnum'
+		list null 'four.lnum'
+		list null 'five.lnum'
+		list null 'six.lnum'
+		list null 'seven.lnum'
+		list null 'eight.lnum'
+		list null 'nine.lnum'
+
 	createMedievalCombs 0 XH : list
 		list 0x363 'a'
 		list 0x364 'e'

font-src/glyphs/symbol/punctuation/slashes-and-number-sign.ptl

@@ -26,7 +26,8 @@ glyph-block Symbol-Punctuation-Slashes-And-Number-Sign : begin
 	create-glyph 'slash' '/' : glyph-proc
 		include : SlashShape slashDefautLeft slashDefaultRight
 
-	alias 'solidus' 0x2044 'slash'
+	alias 'solidus'      0x2044 'slash'
+	alias 'fractionBar'  null   'slash'
 	alias 'mathDivSlash' 0x2215 'slash'
 
 	create-glyph 'doubleSlash' 0x2AFD : glyph-proc

font-src/otl/gsub-frac.ptl

@@ -0,0 +1,50 @@
+import [add-common-feature add-feature add-lookup BeginLookupBlock EndLookupBlock ChainRuleBuilder] from "./table-util"
+import [NumeratorForm DenominatorForm] from "../support/gr"
+
+define-operator "~>" 880 'right' : syntax-rules
+	`(@l ~> @r) `{.left @l .right @r}
+
+# Name-driven feature pairs
+export : define [buildFrac sink glyphStore] : begin
+	local rec : BeginLookupBlock sink
+
+	define frac : add-feature sink 'frac'
+	define { chain-rule reverse-rule } : ChainRuleBuilder sink
+
+	define subSolidus : add-lookup sink : object
+		.type 'gsub_single'
+		.substitutions : object ['solidus' 'fractionBar']
+
+	define digitSet { }
+	define numSet   { }
+	define denSet   { }
+
+	foreach { gid g } [glyphStore.namedEntries] : if (gid.(0) !== ".") : begin
+		local numForm : NumeratorForm.get   g
+		local denForm : DenominatorForm.get g
+		if (numForm && denForm) : begin
+			digitSet.push gid
+			numSet.push   numForm
+			denSet.push   denForm
+
+	define subDen : add-lookup sink : object
+		.type 'gsub_chaining'
+		.rules : list
+			chain-rule [{'fractionBar'}.concat denSet] [digitSet ~> denSet]
+
+	define subNum : add-lookup sink : object
+		.type 'gsub_reverse'
+		.rules : list
+			reverse-rule [digitSet ~> numSet] [{'fractionBar'}.concat numSet]
+
+	frac.lookups.push subSolidus
+	frac.lookups.push subDen
+	frac.lookups.push subNum
+	sink.lookupDep.push {subSolidus subDen}
+	sink.lookupDep.push {subSolidus subNum}
+
+	add-common-feature sink frac
+
+	EndLookupBlock rec sink
+
+define [objectIsNotEmpty obj] : obj && [Object.keys obj].length

font-src/otl/index.ptl

@@ -6,6 +6,7 @@ import [CreateEmptyTable finalizeTable MoveBackUtilityLookups] from "./table-uti
 import [buildLigations] from './gsub-ligation'
 import [buildCCMP] from './gsub-ccmp'
 import [buildGrFeature] from './gsub-gr'
+import [buildFrac] from './gsub-frac'
 import [buildCVSS] from './gsub-cv-ss'
 import [buildLOCL] from './gsub-locl'
 import [buildGsubThousands] from './gsub-thousands'
@@ -35,6 +36,9 @@ define [buildGSUB para glyphStore markGlyphs] : begin
 	# ccmp
 	buildCCMP gsub glyphStore markGlyphs
 
+	# frac
+	buildFrac gsub glyphStore
+
 	# Ligation
 	if para.enableLigation : do
 		define plm : Object.assign {.} para.ligation.defaultBuildup

font-src/support/gr.js

@@ -44,6 +44,8 @@ const Wwid = OtlTaggedProp("Wwid", "WWID");
 const Lnum = OtlTaggedProp("Lnum", "lnum");
 const Onum = OtlTaggedProp("Onum", "onum");
 const AplForm = OtlTaggedProp("AplForm", "APLF");
+const NumeratorForm = OtlTaggedProp("Numerator", "NUMF");
+const DenominatorForm = OtlTaggedProp("Denominator", "DENF");
 
 const CvDecompose = {
 	get(glyph) {
@@ -457,6 +459,8 @@ exports.Wwid = Wwid;
 exports.Lnum = Lnum;
 exports.Onum = Onum;
 exports.AplForm = AplForm;
+exports.NumeratorForm = NumeratorForm;
+exports.DenominatorForm = DenominatorForm;
 
 exports.createGrDisplaySheet = createGrDisplaySheet;
 exports.linkSuffixGr = linkSuffixGr;