Fixing numerical rounding edge case in SkTileGrid

src/core/SkTileGrid.cpp

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkTileGrid.h"
 
@@ skipping 63 matching lines @@
     // by rounding outwards to the nearest tile boundary so that the resulting tile
     // region includes the query rectangle. (using truncating division to "floor")
     int tileStartX = adjustedQuery.left() / fInfo.fTileInterval.width();
     int tileEndX = (adjustedQuery.right() + fInfo.fTileInterval.width() - 1) /
         fInfo.fTileInterval.width();
     int tileStartY = adjustedQuery.top() / fInfo.fTileInterval.height();
     int tileEndY = (adjustedQuery.bottom() + fInfo.fTileInterval.height() - 1) /
         fInfo.fTileInterval.height();
 
     tileStartX = SkPin32(tileStartX, 0, fXTileCount - 1);
-    tileEndX = SkPin32(tileEndX, 1, fXTileCount);
+    tileEndX = SkPin32(tileEndX, tileStartX+1, fXTileCount);
     tileStartY = SkPin32(tileStartY, 0, fYTileCount - 1);
-    tileEndY = SkPin32(tileEndY, 1, fYTileCount);
+    tileEndY = SkPin32(tileEndY, tileStartY+1, fYTileCount);
 
     int queryTileCount = (tileEndX - tileStartX) * (tileEndY - tileStartY);
     SkASSERT(queryTileCount);
     if (queryTileCount == 1) {
         *results = this->tile(tileStartX, tileStartY);
     } else {
         results->reset();
         SkTDArray<int> curPositions;
         curPositions.setCount(queryTileCount);
         // Note: Reserving space for 1024 tile pointers on the stack. If the
@@ skipping 28 matching lines @@
 }
 
 void SkTileGrid::rewindInserts() {
     SkASSERT(fClient);
     for (int i = 0; i < fTileCount; ++i) {
         while (!fTileData[i].isEmpty() && fClient->shouldRewind(fTileData[i].top())) {
             fTileData[i].pop();
         }
     }
 }