1 files changed, 64 insertions, 0 deletions
diff --git a/gfx/skia/skia/src/core/SkScaleToSides.h b/gfx/skia/skia/src/core/SkScaleToSides.h
new file mode 100644
index 0000000000..f9ba845990
--- /dev/null
+++ b/gfx/skia/skia/src/core/SkScaleToSides.h
@@ -0,0 +1,64 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkScaleToSides_DEFINED
+#define SkScaleToSides_DEFINED
+
+#include "include/core/SkScalar.h"
+#include "include/core/SkTypes.h"
+
+#include <cmath>
+#include <utility>
+
+class SkScaleToSides {
+public:
+    // This code assumes that a and b fit in a float, and therefore the resulting smaller value
+    // of a and b will fit in a float. The side of the rectangle may be larger than a float.
+    // Scale must be less than or equal to the ratio limit / (*a + *b).
+    // This code assumes that NaN and Inf are never passed in.
+    static void AdjustRadii(double limit, double scale, SkScalar* a, SkScalar* b) {
+        SkASSERTF(scale < 1.0 && scale > 0.0, "scale: %g", scale);
+
+        *a = (float)((double)*a * scale);
+        *b = (float)((double)*b * scale);
+
+        if (*a + *b > limit) {
+            float* minRadius = a;
+            float* maxRadius = b;
+
+            // Force minRadius to be the smaller of the two.
+            if (*minRadius > *maxRadius) {
+                using std::swap;
+                swap(minRadius, maxRadius);
+            }
+
+            // newMinRadius must be float in order to give the actual value of the radius.
+            // The newMinRadius will always be smaller than limit. The largest that minRadius can be
+            // is 1/2 the ratio of minRadius : (minRadius + maxRadius), therefore in the resulting
+            // division, minRadius can be no larger than 1/2 limit + ULP.
+            float newMinRadius = *minRadius;
+
+            float newMaxRadius = (float)(limit - newMinRadius);
+
+            // Reduce newMaxRadius an ulp at a time until it fits. This usually never happens,
+            // but if it does it could be 1 or 2 times. In certain pathological cases it could be
+            // more. Max iterations seen so far is 17.
+            while (newMaxRadius + newMinRadius > limit) {
+                newMaxRadius = nextafterf(newMaxRadius, 0.0f);
+            }
+            *maxRadius = newMaxRadius;
+        }
+
+        SkASSERTF(*a >= 0.0f && *b >= 0.0f, "a: %g, b: %g, limit: %g, scale: %g", *a, *b, limit,
+                  scale);
+
+        SkASSERTF(*a + *b <= limit,
+                  "\nlimit: %.17f, sum: %.17f, a: %.10f, b: %.10f, scale: %.20f",
+                  limit, *a + *b, *a, *b, scale);
+    }
+};
+#endif // ScaleToSides_DEFINED