Tighten SkAAClip Bounds by Path Bounds

src/core/SkScan_AAAPath.cpp

Index: src/core/SkScan_AAAPath.cpp
diff --git a/src/core/SkScan_AAAPath.cpp b/src/core/SkScan_AAAPath.cpp
index 16b5561a9dbe23b9c3303045e6dd5462872f04de..2f33a0fba5fa4301c22293a395f073732f7d65af 100644
--- a/src/core/SkScan_AAAPath.cpp
+++ b/src/core/SkScan_AAAPath.cpp
@@ -961,9 +961,9 @@ static inline void aaa_walk_convex_edges(SkAnalyticEdge* prevHead, AdditiveBlitt
         }
         local_bot_fixed = SkMin32(local_bot_fixed, SkIntToFixed(stop_y));
 
-        SkFixed left = leftE->fX;
+        SkFixed left = SkTMax(leftBound, leftE->fX);
         SkFixed dLeft = leftE->fDX;
-        SkFixed rite = riteE->fX;
+        SkFixed rite = SkTMin(riteBound, riteE->fX);
         SkFixed dRite = riteE->fDX;
         if (0 == (dLeft | dRite)) {
             int     fullLeft    = SkFixedCeilToInt(left);
@@ -1073,6 +1073,8 @@ static inline void aaa_walk_convex_edges(SkAnalyticEdge* prevHead, AdditiveBlitt
                     SkFixed dY = nextY - y;
                     SkFixed nextLeft = left + SkFixedMul_lowprec(dLeft, dY);
                     SkFixed nextRite = rite + SkFixedMul_lowprec(dRite, dY);
+                    SkASSERT((left & kSnapMask) >= leftBound && (rite & kSnapMask) <= riteBound &&
+                            (nextLeft & kSnapMask) >= leftBound && (nextRite & kSnapMask) <= riteBound);
                     blit_trapezoid_row(blitter, y >> 16, left & kSnapMask, rite & kSnapMask,
                             nextLeft & kSnapMask, nextRite & kSnapMask, leftE->fDY, riteE->fDY,
                             getPartialAlpha(0xFF, dY), maskRow, isUsingMask);
@@ -1088,6 +1090,8 @@ static inline void aaa_walk_convex_edges(SkAnalyticEdge* prevHead, AdditiveBlitt
                         maskRow = static_cast<MaskAdditiveBlitter*>(blitter)->getRow(y >> 16);
                     }
                     SkFixed nextY = y + SK_Fixed1, nextLeft = left + dLeft, nextRite = rite + dRite;
+                    SkASSERT((left & kSnapMask) >= leftBound && (rite & kSnapMask) <= riteBound &&
+                            (nextLeft & kSnapMask) >= leftBound && (nextRite & kSnapMask) <= riteBound);
                     blit_trapezoid_row(blitter, y >> 16, left & kSnapMask, rite & kSnapMask,
                             nextLeft & kSnapMask, nextRite & kSnapMask,
                             leftE->fDY, riteE->fDY, 0xFF, maskRow, isUsingMask);
@@ -1109,6 +1113,8 @@ static inline void aaa_walk_convex_edges(SkAnalyticEdge* prevHead, AdditiveBlitt
             // Note that we substract kSnapHalf later so we have to add them to leftBound/riteBound
             SkFixed nextLeft = SkTMax(left + SkFixedMul_lowprec(dLeft, dY), leftBound + kSnapHalf);
             SkFixed nextRite = SkTMin(rite + SkFixedMul_lowprec(dRite, dY), riteBound + kSnapHalf);
+            SkASSERT((left & kSnapMask) >= leftBound && (rite & kSnapMask) <= riteBound &&
+                    (nextLeft & kSnapMask) >= leftBound && (nextRite & kSnapMask) <= riteBound);
             blit_trapezoid_row(blitter, y >> 16, left & kSnapMask, rite & kSnapMask,
                     nextLeft & kSnapMask, nextRite & kSnapMask, leftE->fDY, riteE->fDY,
                     getPartialAlpha(0xFF, dY), maskRow, isUsingMask);