[instancer/L4] Address review comments

Lib/fontTools/varLib/instancer/__init__.py

@@ -234,9 +234,29 @@ def limitRangeAndPopulateDefault(self, fvarTriple) -> "AxisTriple":
 
 
 @dataclasses.dataclass(frozen=True, order=True, repr=False)
-class NormalizedAxisTripleAndDistances(AxisTriple):
+class NormalizedAxisTrip(AxisTriple):
     """A triple of (min, default, max) normalized axis values."""
 
+    minimum: float
+    default: float
+    maximum: float
+
+    def __post_init__(self):
+        if self.default is None:
+            object.__setattr__(self, "default", max(self.minimum, min(self.maximum, 0)))
+        if not (-1.0 <= self.minimum <= self.default <= self.maximum <= 1.0):
+            raise ValueError(
+                "Normalized axis values not in -1..+1 range; got "
+                f"minimum={self.minimum:g}, default={self.default:g}, maximum={self.maximum:g})"
+            )
+
+
+@dataclasses.dataclass(frozen=True, order=True, repr=False)
+class NormalizedAxisTripleAndDistances(AxisTriple):
+    """A triple of (min, default, max) normalized axis values,
+    with distances between min and default, and default and max,
+    in the *pre-normalized* space."""
+
     minimum: float
     default: float
     maximum: float
@@ -256,7 +276,11 @@ def reverse_negate(self):
         v = self
         return self.__class__(-v[2], -v[1], -v[0], v[4], v[3])
 
-    def normalizeValue(self, v, extrapolate=True):
+    def renormalizeValue(self, v, extrapolate=True):
+        """Renormalizes a normalized value v to the range of this axis,
+        considering the pre-normalized distances as well as the new
+        axis limits."""
+
         lower, default, upper, distanceNegative, distancePositive = self
         assert lower <= default <= upper
 
@@ -267,7 +291,7 @@ def normalizeValue(self, v, extrapolate=True):
             return 0
 
         if default < 0:
-            return -self.reverse_negate().normalizeValue(-v, extrapolate=extrapolate)
+            return -self.reverse_negate().renormalizeValue(-v, extrapolate=extrapolate)
 
         # default >= 0 and v != default
 
@@ -288,12 +312,6 @@ def normalizeValue(self, v, extrapolate=True):
         else:
             vDistance = -v * distanceNegative + distancePositive * default
 
-        if totalDistance == 0:
-            # This happens
-            if default == 0:
-                return -v / lower
-            return 0  # Shouldn't happen
-
         return -vDistance / totalDistance
 
 
@@ -558,7 +576,7 @@ def _instantiateGvarGlyph(
                         "Instancing accross VarComposite axes with variation is not supported."
                     )
                 limits = axisLimits[tag]
-                loc = limits.normalizeValue(loc, extrapolate=False)
+                loc = limits.renormalizeValue(loc, extrapolate=False)
                 newLocation[tag] = loc
             component.location = newLocation
 
@@ -989,10 +1007,10 @@ def instantiateAvar(varfont, axisLimits):
             for fromCoord, toCoord in mapping.items():
                 if fromCoord < axisRange.minimum or fromCoord > axisRange.maximum:
                     continue
-                fromCoord = axisRange.normalizeValue(fromCoord)
+                fromCoord = axisRange.renormalizeValue(fromCoord)
 
                 assert mappedMin <= toCoord <= mappedMax
-                toCoord = mappedAxisLimit.normalizeValue(toCoord)
+                toCoord = mappedAxisLimit.renormalizeValue(toCoord)
 
                 fromCoord = floatToFixedToFloat(fromCoord, 14)
                 toCoord = floatToFixedToFloat(toCoord, 14)

Lib/fontTools/varLib/instancer/featureVars.py

@@ -41,7 +41,7 @@ def _limitFeatureVariationConditionRange(condition, axisLimit):
         return
 
     return tuple(
-        axisLimit.normalizeValue(v, extrapolate=False) for v in (minValue, maxValue)
+        axisLimit.renormalizeValue(v, extrapolate=False) for v in (minValue, maxValue)
     )
 
 
@@ -53,7 +53,7 @@ def _instantiateFeatureVariationRecord(
     newConditions = []
     from fontTools.varLib.instancer import NormalizedAxisTripleAndDistances
 
-    default_triple = NormalizedAxisTripleAndDistances(-1, 0, +1, 0, 0)
+    default_triple = NormalizedAxisTripleAndDistances(-1, 0, +1)
     for i, condition in enumerate(record.ConditionSet.ConditionTable):
         if condition.Format == 1:
             axisIdx = condition.AxisIndex

Lib/fontTools/varLib/instancer/solver.py

@@ -12,7 +12,7 @@ def _reverse_negate(v):
 
 
 def _solve(tent, axisLimit, negative=False):
-    axisMin, axisDef, axisMax, distanceNegative, distancePositive = axisLimit
+    axisMin, axisDef, axisMax, _distanceNegative, _distancePositive = axisLimit
     lower, peak, upper = tent
 
     # Mirror the problem such that axisDef <= peak
@@ -285,7 +285,7 @@ def rebaseTent(tent, axisLimit):
     If tent value is None, that is a special deltaset that should
     be always-enabled (called "gain")."""
 
-    axisMin, axisDef, axisMax, distanceNegative, distancePositive = axisLimit
+    axisMin, axisDef, axisMax, _distanceNegative, _distancePositive = axisLimit
     assert -1 <= axisMin <= axisDef <= axisMax <= +1
 
     lower, peak, upper = tent
@@ -295,7 +295,7 @@ def rebaseTent(tent, axisLimit):
 
     sols = _solve(tent, axisLimit)
 
-    n = lambda v: axisLimit.normalizeValue(v)
+    n = lambda v: axisLimit.renormalizeValue(v)
     sols = [
         (scalar, (n(v[0]), n(v[1]), n(v[2])) if v is not None else None)
         for scalar, v in sols

Tests/varLib/instancer/instancer_test.py

@@ -1950,7 +1950,7 @@ def check_limit_single_var_axis_range(self, var, axisTag, axisRange, expected):
         ],
     )
     def test_positive_var(self, var, axisTag, newMax, expected):
-        axisRange = instancer.NormalizedAxisTripleAndDistances(0, 0, newMax, 1, 1)
+        axisRange = instancer.NormalizedAxisTripleAndDistances(0, 0, newMax)
         self.check_limit_single_var_axis_range(var, axisTag, axisRange, expected)
 
     @pytest.mark.parametrize(
@@ -2094,6 +2094,7 @@ def test_parseLimits_invalid(limits):
 @pytest.mark.parametrize(
     "limits, expected",
     [
+        # 300, 500 come from the font having 100,400,900 fvar axis limits.
         ({"wght": (100, 400)}, {"wght": (-1.0, 0, 0, 300, 500)}),
         ({"wght": (100, 400, 400)}, {"wght": (-1.0, 0, 0, 300, 500)}),
         ({"wght": (100, 300, 400)}, {"wght": (-1.0, -0.5, 0, 300, 500)}),