Fixing SkTileGrid to clamp rather than clip content and querries that are outside the bounds of the…

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 21 matching lines @@
 
 SkTDArray<void *>& SkTileGrid::tile(int x, int y) {
     return fTileData[y * fXTileCount + x];
 }
 
 void SkTileGrid::insert(void* data, const SkIRect& bounds, bool) {
     SkASSERT(!bounds.isEmpty());
     SkIRect dilatedBounds = bounds;
     dilatedBounds.outset(fInfo.fMargin.width(), fInfo.fMargin.height());
     dilatedBounds.offset(fInfo.fOffset);
-    if (!SkIRect::Intersects(dilatedBounds, fGridBounds)) {

[Tom Hudson, 2013/04/09 10:10:50]

Either this code was erroneous, or the new version could end up not adding data
to any tile, right? Something smells wrong here.

-        return;
-    }
 
     // Note: SkIRects are non-inclusive of the right() column and bottom() row,
     // hence the "-1"s in the computations of maxTileX and maxTileY.
     int minTileX = SkMax32(SkMin32(dilatedBounds.left() / fInfo.fTileInterval.width(),
         fXTileCount - 1), 0);
     int maxTileX = SkMax32(SkMin32((dilatedBounds.right() - 1) / fInfo.fTileInterval.width(),
         fXTileCount - 1), 0);
     int minTileY = SkMax32(SkMin32(dilatedBounds.top() / fInfo.fTileInterval.height(),
         fYTileCount -1), 0);
     int maxTileY = SkMax32(SkMin32((dilatedBounds.bottom() -1) / fInfo.fTileInterval.height(),
@@ skipping 13 matching lines @@
     adjustedQuery.offset(fInfo.fOffset);
     // Convert the query rectangle from device coordinates to tile coordinates
     // 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();
-    if (tileStartX >= fXTileCount || tileStartY >= fYTileCount || tileEndX <= 0 || tileEndY <= 0) {
-        return; // query does not intersect the grid
-    }
-    // clamp to grid
-    if (tileStartX < 0) tileStartX = 0;
-    if (tileStartY < 0) tileStartY = 0;
-    if (tileEndX > fXTileCount) tileEndX = fXTileCount;
-    if (tileEndY > fYTileCount) tileEndY = fYTileCount;
+
+    tileStartX = SkClampMinMax(tileStartX, 0, fXTileCount - 1);
+    tileEndX = SkClampMinMax(tileEndX, 1, fXTileCount);
+    tileStartY = SkClampMinMax(tileStartY, 0, fYTileCount - 1);
+    tileEndY = SkClampMinMax(tileEndY, 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
         // malloc becomes a bottleneck, we may consider increasing that number.
         // Typical large web page, say 2k x 16k, would require 512 tiles of
         // size 256 x 256 pixels.
@@ skipping 25 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();
         }
     }
 }