From 3c9ce8715c654d90d0bdbf6a0d6b71b6ea93b58c Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 23 Apr 2024 12:57:14 -0600
Subject: [PATCH] [Condition] Implement ConditionValue

Shift other Condition format numbers.

Implements
https://github.com/adobe-type-tools/opentype-spec-drafts/blob/main/condvalue_spec.md
---
 Lib/fontTools/ttLib/tables/otData.py | 28 +++++++++++++++++++++----
 Lib/fontTools/ttLib/ttGlyphSet.py    | 31 +++++++++++++++++++++-------
 2 files changed, 48 insertions(+), 11 deletions(-)

diff --git a/Lib/fontTools/ttLib/tables/otData.py b/Lib/fontTools/ttLib/tables/otData.py
index 8e4800a9773..3a01f5934f8 100644
--- a/Lib/fontTools/ttLib/tables/otData.py
+++ b/Lib/fontTools/ttLib/tables/otData.py
@@ -3237,6 +3237,26 @@
         "ConditionTableFormat2",
         [
             ("uint16", "Format", None, None, "Format, = 2"),
+            (
+                "int16",
+                "DefaultValue",
+                None,
+                None,
+                "Value at default instance.",
+            ),
+            (
+                "uint32",
+                "VarIdx",
+                None,
+                None,
+                "Variation index to vary the value based on current designspace location.",
+            ),
+        ],
+    ),
+    (
+        "ConditionTableFormat3",
+        [
+            ("uint16", "Format", None, None, "Format, = 3"),
             (
                 "uint8",
                 "ConditionCount",
@@ -3254,9 +3274,9 @@
         ],
     ),
     (
-        "ConditionTableFormat3",
+        "ConditionTableFormat4",
         [
-            ("uint16", "Format", None, None, "Format, = 3"),
+            ("uint16", "Format", None, None, "Format, = 4"),
             (
                 "uint8",
                 "ConditionCount",
@@ -3274,9 +3294,9 @@
         ],
     ),
     (
-        "ConditionTableFormat4",
+        "ConditionTableFormat5",
         [
-            ("uint16", "Format", None, None, "Format, = 4"),
+            ("uint16", "Format", None, None, "Format, = 5"),
             (
                 "Offset24",
                 "ConditionTable",
diff --git a/Lib/fontTools/ttLib/ttGlyphSet.py b/Lib/fontTools/ttLib/ttGlyphSet.py
index e4f035ad669..0c565bceae0 100644
--- a/Lib/fontTools/ttLib/ttGlyphSet.py
+++ b/Lib/fontTools/ttLib/ttGlyphSet.py
@@ -276,8 +276,9 @@ def draw(self, pen):
         self.glyphSet.charStrings[self.name].draw(pen, self.glyphSet.blender)
 
 
-def _evaluateCondition(condition, fvarAxes, location):
+def _evaluateCondition(condition, fvarAxes, location, instancer):
     if condition.Format == 1:
+        # ConditionAxisRange
         axisIndex = condition.AxisIndex
         axisTag = fvarAxes[axisIndex].axisTag
         axisValue = location.get(axisTag, 0)
@@ -285,20 +286,27 @@ def _evaluateCondition(condition, fvarAxes, location):
         maxValue = condition.FilterRangeMaxValue
         return minValue <= axisValue <= maxValue
     elif condition.Format == 2:
+        # ConditionValue
+        value = condition.DefaultValue
+        value += instancer[condition.VarIdx]
+        return value > 0
+    elif condition.Format == 3:
         # ConditionAnd
         for subcondition in condition.ConditionTable:
-            if not _evaluateCondition(subcondition, fvarAxes, location):
+            if not _evaluateCondition(subcondition, fvarAxes, location, instancer):
                 return False
         return True
-    elif condition.Format == 3:
+    elif condition.Format == 4:
         # ConditionOr
         for subcondition in condition.ConditionTable:
-            if _evaluateCondition(subcondition, fvarAxes, location):
+            if _evaluateCondition(subcondition, fvarAxes, location, instancer):
                 return True
         return False
-    elif condition.Format == 4:
+    elif condition.Format == 5:
         # ConditionNegate
-        return not _evaluateCondition(condition.conditionTable, fvarAxes, location)
+        return not _evaluateCondition(
+            condition.conditionTable, fvarAxes, location, instancer
+        )
     else:
         return False  # Unkonwn condition format
 
@@ -319,17 +327,26 @@ def _draw(self, pen, isPointPen):
         glyph = varc.VarCompositeGlyphs.VarCompositeGlyph[idx]
 
         from fontTools.varLib.multiVarStore import MultiVarStoreInstancer
+        from fontTools.varLib.varStore import VarStoreInstancer
 
         fvarAxes = glyphSet.font["fvar"].axes
         instancer = MultiVarStoreInstancer(
             varc.MultiVarStore, fvarAxes, self.glyphSet.location
         )
+        gdef = glyphSet.font.get("GDEF") if "GDEF" in glyphSet.font else None
+        gdefInstancer = VarStoreInstancer(
+            getattr(gdef.table, "VarStore") if gdef is not None else None,
+            fvarAxes,
+            self.glyphSet.location,
+        )
 
         for comp in glyph.components:
 
             if comp.flags & VarComponentFlags.HAVE_CONDITION:
                 condition = varc.ConditionList.ConditionTable[comp.conditionIndex]
-                if not _evaluateCondition(condition, fvarAxes, self.glyphSet.location):
+                if not _evaluateCondition(
+                    condition, fvarAxes, self.glyphSet.location, gdefInstancer
+                ):
                     continue
 
             location = {}