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 48 matching lines @@
             this->tile(x, y).push(data);
         }
     }
     fInsertionCount++;
 }
 
 void SkTileGrid::search(const SkIRect& query, SkTDArray<void*>* results) {
     SkIRect adjustedQuery = query;
     adjustedQuery.inset(fInfo.fMargin.width(), fInfo.fMargin.height());
     adjustedQuery.offset(fInfo.fOffset);
+    adjustedQuery.sort(); // in case the inset inverted the rectangle

[reed1, 2013/04/09 15:56:16]

If we might invert, then (I presume) we are making the query rect smaller (by
fMargin). Why is that? Naively I would have guessed we would, if anything,
enlarge the query rect, to be conservative in which items we return...

     // 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 = SkPin32(tileStartX, 0, fXTileCount - 1);
+    tileEndX = SkPin32(tileEndX, 1, fXTileCount);
+    tileStartY = SkPin32(tileStartY, 0, fYTileCount - 1);
+    tileEndY = SkPin32(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();
         }
     }
 }