factor out computation for dy in SkEdge lines, so we can later try a fix.
git-svn-id: http://skia.googlecode.com/svn/trunk@6198 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkEdge.h b/src/core/SkEdge.h
index 5367862..c36ba24 100644
--- a/src/core/SkEdge.h
+++ b/src/core/SkEdge.h
@@ -14,6 +14,15 @@
#include "SkFDot6.h"
#include "SkMath.h"
+//#ifdef SK_IGNORE_SETLINE_FIX
+#if 1
+ #define SkEdge_Compute_DY(top, y0) ((32 - (y0)) & 63)
+#else
+ // This is correct, as it favors the lower-pixel when y0 is on a 1/2 pixel
+ // boundary, returning 64 instead of the old code, which returns 0.
+ #define SkEdge_Compute_DY(top, y0) ((top << 6) + 32 - (y0))
+#endif
+
struct SkEdge {
enum Type {
kLine_Type,
@@ -118,8 +127,9 @@
}
SkFixed slope = SkFDot6Div(x1 - x0, y1 - y0);
+ const int dy = SkEdge_Compute_DY(top, y0);
- fX = SkFDot6ToFixed(x0 + SkFixedMul(slope, (32 - y0) & 63)); // + SK_Fixed1/2
+ fX = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy)); // + SK_Fixed1/2
fDX = slope;
fFirstY = top;
fLastY = bot - 1;