Rejigger distance field path rect calcs to avoid underflow

src/gpu/batches/GrAADistanceFieldPathRenderer.cpp

 
 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrAADistanceFieldPathRenderer.h"
 
@@ skipping 324 matching lines @@
         scaledBounds.fRight *= scale;
         scaledBounds.fBottom *= scale;
         // move the origin to an integer boundary (gives better results)
         SkScalar dx = SkScalarFraction(scaledBounds.fLeft);
         SkScalar dy = SkScalarFraction(scaledBounds.fTop);
         scaledBounds.offset(-dx, -dy);
         // get integer boundary
         SkIRect devPathBounds;
         scaledBounds.roundOut(&devPathBounds);
         // pad to allow room for antialiasing
-        devPathBounds.outset(SkScalarCeilToInt(kAntiAliasPad), SkScalarCeilToInt(kAntiAliasPad));
-        // move origin to upper left corner
-        devPathBounds.offsetTo(0,0);
+        const int intPad = SkScalarCeilToInt(kAntiAliasPad);
+        // pre-move origin (after outset, will be 0,0)
+        int width = devPathBounds.width();
+        int height = devPathBounds.height();
+        devPathBounds.fLeft = intPad;
+        devPathBounds.fTop = intPad;
+        devPathBounds.fRight = intPad + width;
+        devPathBounds.fBottom = intPad + height;
+        devPathBounds.outset(intPad, intPad);

[joshualitt, 2015/12/18 17:36:45]

I guess this could still overflow if width or height is = int_max.  Do we not
care about that case?

[jvanverth1, 2015/12/18 17:48:42]

We've already caught that case in canDraw() -- we won't try to atlas a path that
big.

 
         // draw path to bitmap
         SkMatrix drawMatrix;
         drawMatrix.setTranslate(-bounds.left(), -bounds.top());
         drawMatrix.postScale(scale, scale);
         drawMatrix.postTranslate(kAntiAliasPad, kAntiAliasPad);
 
         // setup bitmap backing
         SkASSERT(devPathBounds.fLeft == 0);
         SkASSERT(devPathBounds.fTop == 0);
@@ skipping 16 matching lines @@
         rasterClip.setRect(devPathBounds);
         draw.fRC = &rasterClip;
         draw.fClip = &rasterClip.bwRgn();
         draw.fMatrix = &drawMatrix;
         draw.fDst = dst;
 
         draw.drawPathCoverage(path, paint);
 
         // generate signed distance field
         devPathBounds.outset(SK_DistanceFieldPad, SK_DistanceFieldPad);
-        int width = devPathBounds.width();
-        int height = devPathBounds.height();
+        width = devPathBounds.width();
+        height = devPathBounds.height();
         // TODO We should really generate this directly into the plot somehow
         SkAutoSMalloc<1024> dfStorage(width * height * sizeof(unsigned char));
 
         // Generate signed distance field
         SkGenerateDistanceFieldFromA8Image((unsigned char*)dfStorage.get(),
                                            (const unsigned char*)dst.addr(),
                                            dst.width(), dst.height(), dst.rowBytes());
 
         // add to atlas
         SkIPoint16 atlasLocation;
@@ skipping 242 matching lines @@
     geometry.fAntiAlias = random->nextBool();
     geometry.fGenID = random->nextU();
 
     return AADistanceFieldPathBatch::Create(geometry, viewMatrix,
                                             gTestStruct.fAtlas,
                                             &gTestStruct.fPathCache,
                                             &gTestStruct.fPathList);
 }
 
 #endif