check for null-device pixels in onWritePixels, so we don't crash

gm/stroketext.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 "SkCanvas.h"
 
+static void test_nulldev(SkCanvas* canvas) {

[bsalomon, 2014/03/14 14:03:45]

should this be in a unit test?

+    SkBitmap bm;
+    bm.setConfig(SkBitmap::kARGB_8888_Config, 30, 30);
+    // notice: no pixels mom! be sure we don't crash
+    // https://code.google.com/p/chromium/issues/detail?id=352616
+    SkCanvas c(bm);
+
+    SkBitmap src;
+    src.allocN32Pixels(10, 10);
+    src.eraseColor(SK_ColorRED);
+
+    // ensure we don't crash
+    c.writePixels(src, 0, 0);
+}
+
 static void draw_text_stroked(SkCanvas* canvas, const SkPaint& paint) {
     SkPaint p(paint);
     SkPoint loc = { 20, 450 };
 
     canvas->drawText("P", 1, loc.fX, loc.fY - 225, p);
     canvas->drawPosText("P", 1, &loc, p);
 
     p.setColor(SK_ColorRED);
     p.setStyle(SkPaint::kStroke_Style);
     p.setStrokeWidth(10);
@@ skipping 16 matching lines @@
 protected:
     virtual SkString onShortName() SK_OVERRIDE {
         return SkString("stroketext");
     }
 
     virtual SkISize onISize() SK_OVERRIDE {
         return SkISize::Make(640, 480);
     }
 
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        if (true) { test_nulldev(canvas); }
         SkPaint paint;
         paint.setAntiAlias(true);
 
         paint.setTextSize(kBelowThreshold_TextSize);
         draw_text_stroked(canvas, paint);
 
         canvas->translate(200, 0);
         paint.setTextSize(kAboveThreshold_TextSize);
         draw_text_stroked(canvas, paint);
     }
 
 private:
     typedef skiagm::GM INHERITED;
 };
 
 DEF_GM( return SkNEW(StrokeTextGM); )