Fix round cap approximation to understand scale
bug:19772120
Change-Id: I7b944faed1d1e8d5f55453802da57679217d9d9a
diff --git a/libs/hwui/utils/MathUtils.h b/libs/hwui/utils/MathUtils.h
index d89859b..9c3787c 100644
--- a/libs/hwui/utils/MathUtils.h
+++ b/libs/hwui/utils/MathUtils.h
@@ -16,6 +16,8 @@
#ifndef MATHUTILS_H
#define MATHUTILS_H
+#include <math.h>
+
namespace android {
namespace uirenderer {
@@ -62,6 +64,19 @@
return scale;
}
+ /**
+ * Returns the number of points (beyond two, the start and end) needed to form a polygonal
+ * approximation of an arc, with a given threshold value.
+ */
+ inline static int divisionsNeededToApproximateArc(float radius,
+ float angleInRads, float threshold) {
+ const float errConst = (-threshold / radius + 1);
+ const float targetCosVal = 2 * errConst * errConst - 1;
+
+ // needed divisions are rounded up from approximation
+ return (int)(ceilf(angleInRads / acos(targetCosVal)/2)) * 2;
+ }
+
inline static bool areEqual(float valueA, float valueB) {
return isZero(valueA - valueB);
}
