[instancer-solver] port solver fix (#4519)

* [instancer-solver] port solver fix

from https://github.com/fonttools/fonttools/pull/3374

src/hb-subset-instancer-solver.cc

@@ -256,7 +256,10 @@ _solve (Triple tent, Triple axisLimit, bool negative = false)
      */
     float newUpper = peak + (1 - gain) * (upper - peak);
     assert (axisMax <= newUpper);  // Because outGain > gain
-    if (newUpper <= axisDef + (axisMax - axisDef) * 2)
+    /* Disabled because ots doesn't like us:
+     * https://github.com/fonttools/fonttools/issues/3350 */
+    
+    if (false && (newUpper <= axisDef + (axisMax - axisDef) * 2))
     {
       upper = newUpper;
       if (!negative && axisDef + (axisMax - axisDef) * MAX_F2DOT14 < upper)

src/test-subset-instancer-solver.cc

@@ -95,9 +95,11 @@ main (int argc, char **argv)
     Triple tent (0.f, 0.2f, 1.f);
     Triple axis_range (-1.f, 0.f, 0.8f);
     result_t out = rebase_tent (tent, axis_range, default_axis_distances);
-    assert (out.length == 1);
+    assert (out.length == 2);
     assert (out[0].first == 1.f);
-    assert (out[0].second == Triple (0.f, 0.25f, 1.25f));
+    assert (out[0].second == Triple (0.f, 0.25f, 1.f));
+    assert (approx (out[1].first, 0.25f));
+    assert (out[1].second == Triple (0.25f, 1.f, 1.f));
   }
 
   /* Case 3 boundary */
@@ -105,9 +107,11 @@ main (int argc, char **argv)
     Triple tent (0.f, 0.4f, 1.f);
     Triple axis_range (-1.f, 0.f, 0.5f);
     result_t out = rebase_tent (tent, axis_range, default_axis_distances);
-    assert (out.length == 1);
+    assert (out.length == 2);
     assert (out[0].first == 1.f);
-    assert (out[0].second == Triple (0.f, 0.8f, 32767/(float) (1 << 14)));
+    assert (out[0].second == Triple (0.f, 0.8f, 1.f));
+    assert (out[1].first == 2.5f/3);
+    assert (out[1].second == Triple (0.8f, 1.f, 1.f));
   }
 
   /* Case 4 */
@@ -353,9 +357,11 @@ main (int argc, char **argv)
     Triple tent (0.f, 0.2f, 1.f);
     Triple axis_range (0.f, 0.f, 0.5f);
     result_t out = rebase_tent (tent, axis_range, default_axis_distances);
-    assert (out.length == 1);
+    assert (out.length == 2);
     assert (out[0].first == 1.f);
-    assert (out[0].second == Triple (0.f, 0.4f, 32767/(float) (1 << 14)));
+    assert (out[0].second == Triple (0.f, 0.4f, 1.f));
+    assert (out[1].first == 0.625f);
+    assert (out[1].second == Triple (0.4f, 1.f, 1.f));
   }