Further defer devRect computation in gpu rect drawing

src/gpu/GrAARectRenderer.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 "GrAARectRenderer.h"
 #include "GrRefCnt.h"
 #include "GrGpu.h"
@@ skipping 370 matching lines @@
         return;
     }
 
     intptr_t verts = reinterpret_cast<intptr_t>(geo.vertices());
     size_t vsize = drawState->getVertexSize();
     GrAssert(sizeof(GrPoint) + sizeof(GrColor) == vsize);
 
     GrPoint* fan0Pos = reinterpret_cast<GrPoint*>(verts);
     GrPoint* fan1Pos = reinterpret_cast<GrPoint*>(verts + 4 * vsize);
 
-    SkRect devRect;
-    combinedMatrix.mapRect(&devRect, rect);
+    if (combinedMatrix.rectStaysRect()) {
+        SkRect devRect;
+        combinedMatrix.mapRect(&devRect, rect);
 
-    if (combinedMatrix.rectStaysRect()) {
         set_inset_fan(fan0Pos, vsize, devRect, -SK_ScalarHalf, -SK_ScalarHalf);
         set_inset_fan(fan1Pos, vsize, devRect,  SK_ScalarHalf,  SK_ScalarHalf);
     } else {
         // compute transformed (1, 0) and (0, 1) vectors
         SkVector vec[2] = {
           { combinedMatrix[SkMatrix::kMScaleX], combinedMatrix[SkMatrix::kMSkewY] },
           { combinedMatrix[SkMatrix::kMSkewX],  combinedMatrix[SkMatrix::kMScaleY] }
         };
 
         vec[0].normalize();
         vec[0].scale(SK_ScalarHalf);
         vec[1].normalize();
         vec[1].scale(SK_ScalarHalf);
 
+        // create the rotated rect
         fan0Pos->setRectFan(rect.fLeft, rect.fTop,
                             rect.fRight, rect.fBottom, vsize);
         combinedMatrix.mapPointsWithStride(fan0Pos, vsize, 4);
 
+        // Now create the inset points and then outset the original
+        // rotated points
+
         // TL
         *((SkPoint*)((intptr_t)fan1Pos + 0 * vsize)) =
             *((SkPoint*)((intptr_t)fan0Pos + 0 * vsize)) + vec[0] + vec[1];
         *((SkPoint*)((intptr_t)fan0Pos + 0 * vsize)) -= vec[0] + vec[1];
         // BL
         *((SkPoint*)((intptr_t)fan1Pos + 1 * vsize)) =
             *((SkPoint*)((intptr_t)fan0Pos + 1 * vsize)) + vec[0] - vec[1];
         *((SkPoint*)((intptr_t)fan0Pos + 1 * vsize)) -= vec[0] - vec[1];
         // BR
         *((SkPoint*)((intptr_t)fan1Pos + 2 * vsize)) =
@@ skipping 281 matching lines @@
     // The innermost rect has full coverage
     verts += 8 * vsize;
     for (int i = 0; i < 4; ++i) {
         *reinterpret_cast<GrColor*>(verts + i * vsize) = 0;
     }
 
     target->setIndexSourceToBuffer(indexBuffer);
     target->drawIndexed(kTriangles_GrPrimitiveType,
                         0, 0, 16, aaStrokeRectIndexCount());
 }