[instancer.solver] Fix up algorithm again

fonttools · Aug 17, 2022 · d836c6a · d836c6a
1 parent 9196af1
commit d836c6a
Show file tree

Hide file tree

Showing 2 changed files with 35 additions and 9 deletions.
diff --git a/Lib/fontTools/varLib/instancer/solver.py b/Lib/fontTools/varLib/instancer/solver.py
@@ -49,20 +49,36 @@ def _solveWithGain(tent, axisLimit):
     gain = supportScalar({'tag': axisDef}, {'tag': tent})
     out = [(gain, axisLimit)]
 
-
     # First, the positive side
 
+    # case 3a: gain is more than outGain.
+    outGain = supportScalar({'tag': axisMax}, {'tag': tent})
+
+    if gain > outGain:
+
+        crossing = peak + ((1 - gain) * (upper - peak) / (1 - outGain))
+
+        loc1 = (peak, peak, crossing)
+        scalar1 = 1
+
+        loc2 = (crossing, axisMax, axisMax)
+        scalar2 = 0
+
+        out.append((scalar1 - gain, loc1))
+        if (peak < upper):
+            out.append((scalar2 - gain, loc2))
+
     # case 3: outermost limit still fits within F2Dot14 bounds;
     # we keep deltas as is and only scale the axes bounds. Deltas beyond -1.0
     # or +1.0 will never be applied as implementations must clamp to that range.
-    if axisDef + (axisMax - axisDef) * 2 >= upper:
+    elif axisDef + (axisMax - axisDef) * 2 >= upper:
 
         if axisDef + (axisMax - axisDef) * MAX_F2DOT14 < upper:
             # we clamp +2.0 to the max F2Dot14 (~1.99994) for convenience
             upper = axisDef + (axisMax - axisDef) * MAX_F2DOT14
 
         if upper > axisDef:
-            out.append((0 - gain, (axisDef, peak, upper)))
+            out.append((1 - gain, (axisDef, peak, upper)))
 
     # case 4: new limit doesn't fit; we need to chop the deltaset into two 'tents',
     # because the shape of a triangle with part of one side cut off cannot be
@@ -71,7 +87,7 @@ def _solveWithGain(tent, axisLimit):
     else:
 
         loc1 = (axisDef, peak, axisMax)
-        scalar1 = 0
+        scalar1 = 1
 
         loc2 = (peak, axisMax, axisMax)
         scalar2 = supportScalar({'tag': axisMax}, {'tag': tent})

diff --git a/Tests/varLib/instancer/solver_test.py b/Tests/varLib/instancer/solver_test.py
@@ -84,12 +84,22 @@ class RebaseTentTest(object):
             # With gain:
             #
 
-            # Case 1neg
+            # Case 3/1neg
             pytest.param(
                 (.0, .5, 1), (0, .5, 1),
                 [
                     (1, (-1, 0, 1)),
-                    (-1, (0, 0, 1)),
+                    (-1, (0, 1, 1)),
+                    (-1, (-1, -1, 0)),
+                ]
+            ),
+
+            # Case 4/1neg
+            pytest.param(
+                (.0, .5, 2), (0, .5, .8),
+                [
+                    (1, (-1, 0, 1)),
+                    (-1.0, (0.0, 1, 1)),
                     (-1, (-1, -1, 0)),
                 ]
             ),
@@ -99,7 +109,7 @@ class RebaseTentTest(object):
                 (.0, .5, 1), (0, .25, .5),
                 [
                     (.5, (-1, 0, 1)),
-                    (-.5, (0, 1, 1)),
+                    (.5, (0, 1, 1)),
                     (-.5, (-1, -1, 0)),
                 ]
             ),
@@ -109,7 +119,7 @@ class RebaseTentTest(object):
                 (.05, .55, 1), (0, .25, .5),
                 [
                     (.4, (-1.0, 0.0, 1.0)),
-                    (-.4, (0.0, 1.0, 1.0)),
+                    (.5, (0, 1, 1)),
                     (-.4, (-1, -.8, 0)),
                     (-.4, (-1, -1, -.8)),
                 ]
@@ -120,4 +130,4 @@ def test_rebaseTent(self, tent, axisRange, expected):
 
         sol = solver.rebaseTent(tent, axisRange)
 
-        assert sol == expected
+        assert sol == expected, (tent, axisRange)