need to invert the alpha computation for single scanline on innerfill

found by Fuzzer



git-svn-id: http://skia.googlecode.com/svn/trunk@3694 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 5 insertions, 1 deletions

diff --git a/src/core/SkScan_Antihair.cpp b/src/core/SkScan_Antihair.cpp
index 3a60778e8f..6c920adc07 100644
--- a/src/core/SkScan_Antihair.cpp
+++ b/src/core/SkScan_Antihair.cpp
@@ -769,7 +769,11 @@ static void innerstrokedot8(FDot8 L, FDot8 T, FDot8 R, FDot8 B,
 
     int top = T >> 8;
     if (top == ((B - 1) >> 8)) {   // just one scanline high
-        inner_scanline(L, top, R, B - T, blitter);
+        // We want the inverse of B-T, since we're the inner-stroke
+        int alpha = 256 - (B - T);
+        if (alpha) {
+            inner_scanline(L, top, R, alpha, blitter);
+        }
         return;
     }