Add per-vertex coverage field, use in AA rects when alpha tweak is not valid, add relevant sample/gm

Review URL: http://codereview.appspot.com/5181044/



git-svn-id: http://skia.googlecode.com/svn/trunk@2440 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 152 insertions, 0 deletions

diff --git a/samplecode/SampleAARectModes.cpp b/samplecode/SampleAARectModes.cpp
new file mode 100644
index 0000000000..7b9e7d5eb3
--- /dev/null
+++ b/samplecode/SampleAARectModes.cpp
@@ -0,0 +1,152 @@
+/*
+ * Copyright 2011 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SampleCode.h"
+#include "SkView.h"
+#include "SkCanvas.h"
+#include "SkDevice.h"
+#include "SkColorPriv.h"
+#include "SkShader.h"
+
+static SkCanvas* create_canvas(int w, int h) {
+    SkBitmap bm;
+    bm.setConfig(SkBitmap::kARGB_8888_Config, w, h);
+    bm.allocPixels();
+    bm.eraseColor(0);
+    return new SkCanvas(bm);
+}
+
+static const SkBitmap& extract_bitmap(SkCanvas* canvas) {
+    return canvas->getDevice()->accessBitmap(false);
+}
+
+static const struct {
+    SkXfermode::Mode  fMode;
+    const char*         fLabel;
+} gModes[] = {
+    { SkXfermode::kClear_Mode,    "Clear"     },
+    { SkXfermode::kSrc_Mode,      "Src"       },
+    { SkXfermode::kDst_Mode,      "Dst"       },
+    { SkXfermode::kSrcOver_Mode,  "SrcOver"   },
+    { SkXfermode::kDstOver_Mode,  "DstOver"   },
+    { SkXfermode::kSrcIn_Mode,    "SrcIn"     },
+    { SkXfermode::kDstIn_Mode,    "DstIn"     },
+    { SkXfermode::kSrcOut_Mode,   "SrcOut"    },
+    { SkXfermode::kDstOut_Mode,   "DstOut"    },
+    { SkXfermode::kSrcATop_Mode,  "SrcATop"   },
+    { SkXfermode::kDstATop_Mode,  "DstATop"   },
+    { SkXfermode::kXor_Mode,      "Xor"       },
+};
+
+const int gWidth = 64;
+const int gHeight = 64;
+const SkScalar W = SkIntToScalar(gWidth);
+const SkScalar H = SkIntToScalar(gHeight);
+
+static SkScalar drawCell(SkCanvas* canvas, SkXfermode* mode,
+                         SkAlpha a0, SkAlpha a1) {
+
+    SkPaint paint;
+    paint.setAntiAlias(true);
+
+    SkRect r = SkRect::MakeWH(W, H);
+    r.inset(W/10, H/10);
+
+    paint.setColor(SK_ColorBLUE);
+    paint.setAlpha(a0);
+    canvas->drawOval(r, paint);
+
+    paint.setColor(SK_ColorRED);
+    paint.setAlpha(a1);
+    paint.setXfermode(mode);
+
+    SkScalar offset = SK_Scalar1 / 3;
+    SkRect rect = SkRect::MakeXYWH(W / 4 + offset,
+                                   H / 4 + offset,
+                                   W / 2, H / 2);
+    canvas->drawRect(rect, paint);
+    
+    return H;
+}
+
+static SkShader* make_bg_shader() {
+    SkBitmap bm;
+    bm.setConfig(SkBitmap::kARGB_8888_Config, 2, 2);
+    bm.allocPixels();
+    *bm.getAddr32(0, 0) = *bm.getAddr32(1, 1) = 0xFFFFFFFF;
+    *bm.getAddr32(1, 0) = *bm.getAddr32(0, 1) = SkPackARGB32(0xFF, 0xCC,
+                                                             0xCC, 0xCC);
+
+    SkShader* s = SkShader::CreateBitmapShader(bm,
+                                               SkShader::kRepeat_TileMode,
+                                               SkShader::kRepeat_TileMode);
+    
+    SkMatrix m;
+    m.setScale(SkIntToScalar(6), SkIntToScalar(6));
+    s->setLocalMatrix(m);
+    return s;
+}
+
+class AARectsModesView : public SampleView {
+    SkPaint fBGPaint;
+public:
+    AARectsModesView () {
+        fBGPaint.setShader(make_bg_shader())->unref();
+    }
+
+protected:
+    // overrides from SkEventSink
+    virtual bool onQuery(SkEvent* evt) {
+        if (SampleCode::TitleQ(*evt)) {
+            SampleCode::TitleR(evt, "AARectsModes");
+            return true;
+        }
+        return this->INHERITED::onQuery(evt);
+    }
+
+    virtual void onDrawContent(SkCanvas* canvas) {
+        const SkRect bounds = SkRect::MakeWH(W, H);
+        static const SkAlpha gAlphaValue[] = { 0xFF, 0x88, 0x88 };
+
+        canvas->translate(SkIntToScalar(4), SkIntToScalar(4));
+
+        for (int alpha = 0; alpha < 4; ++alpha) {
+            canvas->save();
+            canvas->save();
+            for (size_t i = 0; i < SK_ARRAY_COUNT(gModes); ++i) {
+                if (6 == i) {
+                    canvas->restore();
+                    canvas->translate(W * 5, 0);
+                    canvas->save();
+                }
+                SkXfermode* mode = SkXfermode::Create(gModes[i].fMode);
+                
+                canvas->drawRect(bounds, fBGPaint);
+                canvas->saveLayer(&bounds, NULL);
+                SkScalar dy = drawCell(canvas, mode,
+                                       gAlphaValue[alpha & 1],
+                                       gAlphaValue[alpha & 2]);
+                canvas->restore();
+
+                canvas->translate(0, dy * 5 / 4);
+                SkSafeUnref(mode);
+            }
+            canvas->restore();
+            canvas->restore();
+            canvas->translate(W * 5 / 4, 0);
+        }
+    }
+    
+private:
+    typedef SampleView INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+static SkView* MyFactory() { return new AARectsModesView; }
+static SkViewRegister reg(MyFactory);
+