Add xfermodes2 GM. Tests all xfer modes with two gradient bitmaps

gm/xfermodes2.cpp

Index: gm/xfermodes2.cpp
===================================================================
--- gm/xfermodes2.cpp	(revision 0)
+++ gm/xfermodes2.cpp	(revision 0)
@@ -0,0 +1,160 @@
+
+/*
+ * Copyright 2013 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"
+#include "SkShader.h"
+#include "SkXfermode.h"
+#include "SkColorPriv.h"
+
+namespace skiagm {
+
+class Xfermodes2GM : public GM {
+public:
+    Xfermodes2GM() {}
+
+protected:
+    virtual SkString onShortName() SK_OVERRIDE {
+        return SkString("xfermodes2");
+    }
+
+    virtual SkISize onISize() SK_OVERRIDE {
+        return make_isize(455, 475);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        canvas->translate(SkIntToScalar(10), SkIntToScalar(20));
+
+        const SkScalar w = SkIntToScalar(kSize);
+        const SkScalar h = SkIntToScalar(kSize);
+
+        SkPaint labelP;
+        labelP.setAntiAlias(true);
+        labelP.setTextAlign(SkPaint::kCenter_Align);
+
+        const int W = 6;
+
+        SkScalar x = 0, y = 0;
+        for (size_t m = 0; m <= SkXfermode::kLastMode; m++) {
+            SkXfermode::Mode mode = static_cast<SkXfermode::Mode>(m);
+            SkXfermode* xm = SkXfermode::Create(mode);
+            SkAutoUnref aur(xm);
+
+            canvas->save();
+
+            canvas->translate(x, y);
+            SkPaint p;
+            p.setAntiAlias(false);
+            p.setStyle(SkPaint::kFill_Style);
+            p.setShader(fBG);
+            SkRect r = SkRect::MakeWH(w, h);
+            canvas->drawRect(r, p);
+
+            canvas->saveLayer(&r, NULL, SkCanvas::kARGB_ClipLayer_SaveFlag);
+
+            p.setShader(fDst);
+            canvas->drawRect(r, p);
+            p.setShader(fSrc);
+            p.setXfermode(xm);
+            canvas->drawRect(r, p);
+
+            canvas->restore();
+
+            r.inset(-SK_ScalarHalf, -SK_ScalarHalf);
+            p.setStyle(SkPaint::kStroke_Style);
+            p.setShader(NULL);
+            p.setXfermode(NULL);
+            canvas->drawRect(r, p);
+
+            canvas->restore();
+
+#if 1
+            canvas->drawText(SkXfermode::ModeName(mode), strlen(SkXfermode::ModeName(mode)),
+                             x + w/2, y - labelP.getTextSize()/2, labelP);
+#endif
+            x += w + SkIntToScalar(10);
+            if ((m % W) == W - 1) {
+                x = 0;
+                y += h + SkIntToScalar(30);
+            }
+        }
+    }
+
+private:
+    virtual void onOnceBeforeDraw() SK_OVERRIDE {
+        const uint32_t kCheckData[] = {
+            SkPackARGB32(0xFF, 0x40, 0x40, 0x40),
+            SkPackARGB32(0xFF, 0xD0, 0xD0, 0xD0),
+            SkPackARGB32(0xFF, 0xD0, 0xD0, 0xD0),
+            SkPackARGB32(0xFF, 0x40, 0x40, 0x40)
+        };
+        SkBitmap bg;
+        bg.setConfig(SkBitmap::kARGB_8888_Config, 2, 2);
+        bg.allocPixels();
+        SkAutoLockPixels bgAlp(bg);
+        memcpy(bg.getPixels(), kCheckData, sizeof(kCheckData));
+        bg.setIsOpaque(true);
+        
+        fBG.reset(SkShader::CreateBitmapShader(bg,
+                                               SkShader::kRepeat_TileMode,
+                                               SkShader::kRepeat_TileMode));
+        SkMatrix lm;
+        lm.setScale(SkIntToScalar(16), SkIntToScalar(16));
+        fBG->setLocalMatrix(lm);
+        
+        SkBitmap dstBmp;
+        dstBmp.setConfig(SkBitmap::kARGB_8888_Config, kSize, kSize);
+        dstBmp.allocPixels();
+        SkAutoLockPixels dstAlp(dstBmp);
+        SkPMColor* pixels = reinterpret_cast<SkPMColor*>(dstBmp.getPixels());
+        
+        for (int y = 0; y < kSize; ++y) {
+            int c = y * (1 << kShift);
+            SkPMColor rowColor = SkPackARGB32(c, c, 0, c/2);
+            for (int x = 0; x < kSize; ++x) {
+                pixels[kSize * y + x] = rowColor;
+            }
+        }
+        fSrc.reset(SkShader::CreateBitmapShader(dstBmp,
+                                                SkShader::kClamp_TileMode,
+                                                SkShader::kClamp_TileMode));
+        SkBitmap srcBmp;
+        srcBmp.setConfig(SkBitmap::kARGB_8888_Config, kSize, kSize);
+        srcBmp.allocPixels();
+        SkAutoLockPixels srcAlp(srcBmp);
+        pixels = reinterpret_cast<SkPMColor*>(srcBmp.getPixels());
+        
+        for (int x = 0; x < kSize; ++x) {
+            int c = x * (1 << kShift);
+            SkPMColor colColor = SkPackARGB32(c, 0, c, c/2);
+            for (int y = 0; y < kSize; ++y) {
+                pixels[kSize * y + x] = colColor;
+            }
+        }
+        fDst.reset(SkShader::CreateBitmapShader(srcBmp,
+                                                SkShader::kClamp_TileMode,
+                                                SkShader::kClamp_TileMode));
+    }
+    
+    enum {
+        kShift = 2,
+        kSize = 256 >> kShift,
+    };
+    
+    SkAutoTUnref<SkShader> fBG;
+    SkAutoTUnref<SkShader> fSrc;
+    SkAutoTUnref<SkShader> fDst;
+
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static GM* MyFactory(void*) { return new Xfermodes2GM; }
+static GMRegistry reg(MyFactory);
+
+}