Added bench to test multiple readPixels case

https://codereview.appspot.com/6501081/



git-svn-id: http://skia.googlecode.com/svn/trunk@5381 2bbb7eff-a529-9590-31e7-b0007b416f81

bench/ReadPixBench.cpp

@@ -0,0 +1,66 @@
+
+/*
+ * Copyright 2012 The Android Open Source Project
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkBenchmark.h"
+#include "SkCanvas.h"
+
+
+/**
+ * This bench mark tests the use case where the user writes the a canvas
+ * and then reads small chunks from it repeatedly. This can cause trouble
+ * for the GPU as readbacks are very expensive.
+ */
+class ReadPixBench : public SkBenchmark {
+public:
+    ReadPixBench(void* param) : INHERITED(param) {}
+
+protected:
+    virtual const char* onGetName() SK_OVERRIDE {
+        return "readpix";
+    }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        canvas->clear(SK_ColorBLACK);
+
+        SkISize size = canvas->getDeviceSize();
+
+        int offX = (size.width() - kWindowSize) / kNumStepsX;
+        int offY = (size.height() - kWindowSize) / kNumStepsY;
+
+        SkPaint paint;
+
+        paint.setColor(SK_ColorBLUE);
+
+        canvas->drawCircle(SkIntToScalar(size.width()/2), 
+                           SkIntToScalar(size.height()/2), 
+                           SkIntToScalar(size.width()/2),
+                           paint);
+
+        SkBitmap bitmap;
+
+        bitmap.setConfig(SkBitmap::kARGB_8888_Config, kWindowSize, kWindowSize);
+
+        for (int x = 0; x < kNumStepsX; ++x) {
+            for (int y = 0; y < kNumStepsY; ++y) {
+                canvas->readPixels(&bitmap, x * offX, y * offY);
+            }
+        }
+    }
+
+private:
+    static const int kNumStepsX = 30;
+    static const int kNumStepsY = 30;
+    static const int kWindowSize = 5;
+
+    typedef SkBenchmark INHERITED;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+static SkBenchmark* fact(void* p) { return new ReadPixBench(p); }
+static BenchRegistry gReg(fact);

gyp/bench.gypi

@@ -27,6 +27,7 @@
     '../bench/PathIterBench.cpp',
     '../bench/PicturePlaybackBench.cpp',
     '../bench/PictureRecordBench.cpp',
+    '../bench/ReadPixBench.cpp',
     '../bench/RectBench.cpp',
     '../bench/RefCntBench.cpp',
     '../bench/RegionBench.cpp',