add isRect() check to AAClip, to detect if a soft-clip is really just an irect

src/core/SkAAClip.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAAClip.h"
 #include "SkBlitter.h"
@@ skipping 666 matching lines @@
     return this->setPath(path);
 #else
     this->freeRuns();
     fBounds = bounds;
     fRunHead = RunHead::AllocRect(bounds);
     SkASSERT(!this->isEmpty());
     return true;
 #endif
 }
 
+bool SkAAClip::isRect() const {
+    if (this->isEmpty()) {
+        return false;
+    }
+
+    const RunHead* head = fRunHead;
+    if (head->fRowCount != 1) {
+        return false;
+    }
+    const YOffset* yoff = head->yoffsets();
+    if (yoff->fY != fBounds.fBottom - 1) {
+        return false;
+    }
+
+    const uint8_t* row = head->data() + yoff->fOffset;
+    int width = fBounds.width();
+    do {
+        if (row[1] != 0xFF) {
+            return false;
+        }
+        int n = row[0];
+        SkASSERT(n <= width);
+        width -= n;
+        row += 2;
+    } while (width > 0);
+    return true;
+}
+
 bool SkAAClip::setRect(const SkRect& r, bool doAA) {
     if (r.isEmpty()) {
         return this->setEmpty();
     }
 
     AUTO_AACLIP_VALIDATE(*this);
 
     // TODO: special case this
 
     SkPath path;
@@ skipping 1463 matching lines @@
             rowMask.fBounds.fBottom = y + 1;
             fBlitter->blitMask(rowMask, rowMask.fBounds);
             src = (const void*)((const char*)src + srcRB);
         } while (++y < localStopY);
     } while (y < stopY);
 }
 
 const SkBitmap* SkAAClipBlitter::justAnOpaqueColor(uint32_t* value) {
     return NULL;
 }