SkPictureShader should handle negative scaling gracefully.

gm/pictureshader.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 "gm.h"
 
 #include "SkBitmap.h"
@@ skipping 33 matching lines @@
 protected:
     uint32_t onGetFlags() const SK_OVERRIDE {
         return kSkipTiled_Flag;
     }
 
     SkString onShortName() SK_OVERRIDE {
         return SkString("pictureshader");
     }
 
     SkISize onISize() SK_OVERRIDE {
-        return SkISize::Make(1400, 1250);
+        return SkISize::Make(1400, 1450);
     }
 
     void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         this->drawSceneColumn(canvas, SkPoint::Make(0, 0), 1, 1, 0);
         this->drawSceneColumn(canvas, SkPoint::Make(0, fSceneSize * 6.4f), 1, 2, 0);
         this->drawSceneColumn(canvas, SkPoint::Make(fSceneSize * 2.4f, 0), 1, 1, 1);
         this->drawSceneColumn(canvas, SkPoint::Make(fSceneSize * 2.4f, fSceneSize * 6.4f), 1, 1, 2);
         this->drawSceneColumn(canvas, SkPoint::Make(fSceneSize * 4.8f, 0), 2, 1, 0);
         this->drawSceneColumn(canvas, SkPoint::Make(fSceneSize * 9.6f, 0), 2, 2, 0);
+
+        // One last custom row to exercise negative scaling
+        SkMatrix ctm, localMatrix;
+        ctm.setTranslate(fSceneSize * 2.1f, fSceneSize * 13.8f);
+        ctm.preScale(-1, -1);
+        localMatrix.setScale(2, 2);
+        this->drawScene(canvas, ctm, localMatrix, 0);
+
+        ctm.setTranslate(fSceneSize * 2.4f, fSceneSize * 12.8f);
+        localMatrix.setScale(-1, -1);
+        this->drawScene(canvas, ctm, localMatrix, 0);
+
+        ctm.setTranslate(fSceneSize * 4.8f, fSceneSize * 12.3f);
+        ctm.preScale(2, 2);
+        this->drawScene(canvas, ctm, localMatrix, 0);
+
+        ctm.setTranslate(fSceneSize * 13.8f, fSceneSize * 14.3f);
+        ctm.preScale(-2, -2);
+        localMatrix.setTranslate(fTileSize / 4, fTileSize / 4);
+        localMatrix.preRotate(45);
+        localMatrix.preScale(-2, -2);
+        this->drawScene(canvas, ctm, localMatrix, 0);
     }
 
 private:
     void drawSceneColumn(SkCanvas* canvas, const SkPoint& pos, SkScalar scale, SkScalar localScale,
                          unsigned tileMode) {
         SkMatrix ctm, localMatrix;
 
         ctm.setTranslate(pos.x(), pos.y());
         ctm.preScale(scale, scale);
         localMatrix.setScale(localScale, localScale);
@@ skipping 80 matching lines @@
     SkScalar    fTileSize;
     SkScalar    fSceneSize;
 
     SkAutoTUnref<SkPicture> fPicture;
     SkBitmap fBitmap;
 
     typedef GM INHERITED;
 };
 
 DEF_GM( return SkNEW_ARGS(PictureShaderGM, (50, 100)); )