Merge pull request #1718 from googlefonts/gen-kern

[fontra-workflow] Add generate-kern-feature filter, as an alternative to ufo2ft's kern feature generator

src/fontra/workflow/actions/features.py

@@ -185,22 +185,18 @@ async def processFeatures(self, features: OpenTypeFeatures) -> OpenTypeFeatures:
         return OpenTypeFeatures(text=featureText)
 
 
-vkrnTopPrefix = "kern.top."
-vkrnBottomPrefix = "kern.bottom."
+class BaseGenerateKerningFeature(BaseFilter):
+    _kernFeatureTag = "kern"
+    _kern1Prefix = "public.kern1."
+    _kern2Prefix = "public.kern2."
+    _dropKernAttrName = "dropKern"
 
-
-def _kernKeySortFunc(item):
-    key, _ = item
-    return key.startswith(vkrnTopPrefix) or key.startswith(vkrnBottomPrefix)
-
-
-@registerFilterAction("generate-vkrn-feature")
-@dataclass(kw_only=True)
-class GenerateVkrnFeature(BaseFilter):
-    dropVkrn: bool = True
+    def _kernKeySortFunc(self, item):
+        key, _ = item
+        return key.startswith(self._kern1Prefix) or key.startswith(self._kern2Prefix)
 
     async def processFeatures(self, features: OpenTypeFeatures) -> OpenTypeFeatures:
-        verticalKerning = (await self.inputKerning).get("vkrn")
+        verticalKerning = (await self.inputKerning).get(self._kernFeatureTag)
         if verticalKerning is None:
             return features
 
@@ -226,16 +222,16 @@ async def processFeatures(self, features: OpenTypeFeatures) -> OpenTypeFeatures:
         for groupName, group in sorted(verticalKerning.groups.items()):
             w.addGroup(groupName, group)
 
-        fea = w.addFeature("vkrn")
+        fea = w.addFeature(self._kernFeatureTag)
 
         for left, rightDict in sorted(
-            verticalKerning.values.items(), key=_kernKeySortFunc
+            verticalKerning.values.items(), key=self._kernKeySortFunc
         ):
-            if left.startswith(vkrnTopPrefix):
+            if left.startswith(self._kern1Prefix):
                 left = "@" + left
 
-            for right, values in sorted(rightDict.items(), key=_kernKeySortFunc):
-                if right.startswith(vkrnBottomPrefix):
+            for right, values in sorted(rightDict.items(), key=self._kernKeySortFunc):
+                if right.startswith(self._kern2Prefix):
                     right = "@" + right
 
                 values = [0 if v is None else round(v) for v in values]
@@ -264,10 +260,27 @@ async def getKerning(
         kerning = await self.inputKerning
         return (
             kerning
-            if not self.dropVkrn
+            if not getattr(self, self._dropKernAttrName)
             else {
                 kernType: kernTable
                 for kernType, kernTable in kerning.items()
-                if kernType != "vkrn"
+                if kernType != self._kernFeatureTag
             }
         )
+
+
+@registerFilterAction("generate-kern-feature")
+@dataclass(kw_only=True)
+class GenerateKernFeature(BaseGenerateKerningFeature):
+    dropKern: bool = True
+
+
+@registerFilterAction("generate-vkrn-feature")
+@dataclass(kw_only=True)
+class GenerateVkrnFeature(BaseGenerateKerningFeature):
+    dropVkrn: bool = True
+
+    _kernFeatureTag = "vkrn"
+    _kern1Prefix = "kern.top."
+    _kern2Prefix = "kern.bottom."
+    _dropKernAttrName = "dropVkrn"

test-py/data/workflow/output-generate-kern-feature.fontra/features.txt

@@ -0,0 +1,4 @@
+
+feature kern {
+    pos A B (wdth=0,wght=100:-10 wdth=0,wght=900:-20 wdth=1000,wght=100:-15 wdth=1000,wght=900:-25);
+} kern;

test-py/data/workflow/output-generate-kern-feature.fontra/font-data.json

@@ -0,0 +1,179 @@
+{
+"axes": {
+"axes": [
+{
+"name": "width",
+"label": "width",
+"tag": "wdth",
+"minValue": 0,
+"defaultValue": 0,
+"maxValue": 1000
+},
+{
+"name": "weight",
+"label": "weight",
+"tag": "wght",
+"minValue": 100,
+"defaultValue": 100,
+"maxValue": 900,
+"mapping": [
+[
+100,
+150
+],
+[
+900,
+850
+]
+]
+}
+]
+},
+"sources": {
+"3aa9223b": {
+"name": "Support",
+"location": {
+"weight": 595,
+"width": 0
+},
+"lineMetricsHorizontalLayout": {
+"ascender": {
+"value": 800,
+"zone": 16
+},
+"capHeight": {
+"value": 750,
+"zone": 16
+},
+"xHeight": {
+"value": 500,
+"zone": 16
+},
+"baseline": {
+"value": 0,
+"zone": -16
+},
+"descender": {
+"value": -250,
+"zone": -16
+}
+}
+},
+"5bea6334": {
+"name": "LightCondensed",
+"location": {
+"weight": 150,
+"width": 0
+},
+"lineMetricsHorizontalLayout": {
+"ascender": {
+"value": 800,
+"zone": 16
+},
+"capHeight": {
+"value": 750,
+"zone": 16
+},
+"xHeight": {
+"value": 500,
+"zone": 16
+},
+"baseline": {
+"value": 0,
+"zone": -16
+},
+"descender": {
+"value": -250,
+"zone": -16
+}
+}
+},
+"5d4e7f1d": {
+"name": "BoldWide",
+"location": {
+"weight": 850,
+"width": 1000
+},
+"lineMetricsHorizontalLayout": {
+"ascender": {
+"value": 800,
+"zone": 16
+},
+"capHeight": {
+"value": 750,
+"zone": 16
+},
+"xHeight": {
+"value": 500,
+"zone": 16
+},
+"baseline": {
+"value": 0,
+"zone": -16
+},
+"descender": {
+"value": -250,
+"zone": -16
+}
+}
+},
+"d7abd222": {
+"name": "LightWide",
+"location": {
+"weight": 150,
+"width": 1000
+},
+"lineMetricsHorizontalLayout": {
+"ascender": {
+"value": 800,
+"zone": 16
+},
+"capHeight": {
+"value": 750,
+"zone": 16
+},
+"xHeight": {
+"value": 500,
+"zone": 16
+},
+"baseline": {
+"value": 0,
+"zone": -16
+},
+"descender": {
+"value": -250,
+"zone": -16
+}
+}
+},
+"f22d1bbd": {
+"name": "BoldCondensed",
+"location": {
+"weight": 850,
+"width": 0
+},
+"lineMetricsHorizontalLayout": {
+"ascender": {
+"value": 800,
+"zone": 16
+},
+"capHeight": {
+"value": 750,
+"zone": 16
+},
+"xHeight": {
+"value": 500,
+"zone": 16
+},
+"baseline": {
+"value": 0,
+"zone": -16
+},
+"descender": {
+"value": -250,
+"zone": -16
+}
+}
+}
+}
+}

test-py/data/workflow/output-generate-kern-feature.fontra/glyph-info.csv

@@ -0,0 +1,3 @@
+glyph name;code points
+A;U+0041,U+0061
+B;U+0042,U+0062