instancer: sort axisValues so format 4 are dominant for constructing names

Lib/fontTools/varLib/instancer.py

@@ -1366,8 +1366,29 @@ def axisValuesFromAxisLimits(stat, axisLimits):
         raise ValueError(f"Cannot find AxisValue for {', '.join(missing)}")
     # filter out Elidable axisValues
     axisValues = [a for a in axisValues if a.Flags & ELIDABLE_AXIS_VALUE_NAME != 2]
-    # TODO sort and remove duplicates so format 4 axisValues are dominant
-    return axisValues
+    return sortedAxisValues(axisValues)
+
+
+def sortedAxisValues(axisValues):
+    # Sort and remove duplicates so format 4 axisValues are dominant
+    results, seenAxes = [], set()
+    format4 = sorted(
+        [a for a in axisValues if a.Format == 4],
+        key=lambda k: len(k.AxisValueRecord), reverse=True
+    )
+    nonFormat4 = [a for a in axisValues if a not in format4]
+
+    for axisValue in format4:
+        axes = set([r.AxisIndex for r in axisValue.AxisValueRecord])
+        if seenAxes - axes == seenAxes:
+            seenAxes |= axes
+            results.append((tuple(axes), axisValue))
+
+    for axisValue in nonFormat4:
+        axisIndex = axisValue.AxisIndex
+        if axisIndex not in seenAxes:
+            results.append(((axisIndex,), axisValue))
+    return [v for k, v in sorted(results)]
 
 
 def updateNameTable(varfont, axisLimits):

Tests/varLib/instancer_test.py

@@ -2032,6 +2032,33 @@ def test_updateNameTable_vf_with_italic_attribute(varfont):
     assert names[(17, 3, 1, 0x409)] == "Black Condensed Italic"
 
 
+def test_updateNameTable_format4_axisValues(varfont):
+    # format 4 axisValues should dominate the other axisValues
+    stat = varfont["STAT"].table
+
+    axisValue = otTables.AxisValue()
+    axisValue.Format = 4
+    axisValue.Flags = 0
+    varfont["name"].setName("Dominant Value", 297, 3, 1, 0x409)
+    axisValue.ValueNameID = 297
+    axisValue.AxisValueRecord = []
+    for tag, value in (("wght", 900), ("wdth", 79)):
+        rec = otTables.AxisValueRecord()
+        rec.AxisIndex = next(
+            i for i, a in enumerate(stat.DesignAxisRecord.Axis) if a.AxisTag == tag
+        )
+        rec.Value = value
+        axisValue.AxisValueRecord.append(rec)
+    stat.AxisValueArray.AxisValue.append(axisValue)
+
+    instancer.updateNameTable(varfont, {"wdth": 79, "wght": 900})
+    names = _get_name_records(varfont)
+    assert names[(1, 3, 1, 0x409)] == "Test Variable Font Dominant Value"
+    assert names[(2, 3, 1, 0x409)] == "Regular"
+    assert names[(16, 3, 1, 0x409)] == "Test Variable Font"
+    assert names[(17, 3, 1, 0x409)] == "Dominant Value"
+
+
 def test_sanityCheckVariableTables(varfont):
     font = ttLib.TTFont()
     with pytest.raises(ValueError, match="Missing required table fvar"):