Added megalooper GM

gm/megalooper.cpp

+/*
+ * 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 "SkCanvas.h"
+#include "SkBlurMaskFilter.h"
+#include "SkLayerDrawLooper.h"
+#include "SkColorFilter.h"
+
+// This GM tests 3 different ways of drawing four shadows around a square:
+//      just using 4 blurred rects
+//      using 4 1-level draw loopers
+//      using 1 4-level draw looper
+// They all produce exactly the same pixels
+class MegaLooperGM : public skiagm::GM {
+public:
+    // The types define "<# of loopers> x <# of stages per looper>"
+    enum Type {
+        k0x0_Type,  // draw without loopers at all
+        k4x1_Type,  // a looper for each shadow
+        k1x4_Type,  // all four shadows in one looper
+    };
+
+    MegaLooperGM(Type type) : fType(type) {}
+
+protected:
+    virtual SkString onShortName() {
+        switch (fType) {
+        case k0x0_Type:
+            return SkString("megalooper_0x0");
+            break;
+        case k4x1_Type:
+            return SkString("megalooper_4x1");
+            break;
+        case k1x4_Type:     // fall through
+        default:
+            return SkString("megalooper_1x4");
+            break;
+        }
+    }
+
+    virtual SkISize onISize() {
+        return SkISize::Make(kWidth, kHeight);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) {
+        for (int y = 100; y < kHeight; y += 200) {
+            for (int x = 100; x < kWidth; x += 200) {
+                switch (fType) {
+                    case k0x0_Type:
+                        draw0x0(canvas, SkIntToScalar(x), SkIntToScalar(y));
+                        break;
+                    case k4x1_Type:
+                        draw4x1(canvas, SkIntToScalar(x), SkIntToScalar(y));
+                        break;
+                    case k1x4_Type:     // fall through
+                    default:
+                        draw1x4(canvas, SkIntToScalar(x), SkIntToScalar(y));
+                        break;
+                }
+            }
+        }
+    }
+
+private:
+    static const int kWidth = 800;
+    static const int kHeight = 800;
+    static const int kHalfOuterClipSize = 100;
+    static const int kHalfSquareSize = 50;
+    static const int kOffsetToOutsideClip = kHalfSquareSize + kHalfOuterClipSize + 1;
+
+    static const SkPoint gBlurOffsets[4];
+    static const SkColor gColors[4];
+    Type fType;
+
+    // Just draw a blurred rect at each of the four corners of a square (centered at x,y).
+    // Use two clips to define a rectori where we want pixels to appear.
+    void draw0x0(SkCanvas* canvas, SkScalar x, SkScalar y) {
+        SkRect innerClip = { -kHalfSquareSize, -kHalfSquareSize, kHalfSquareSize, kHalfSquareSize };
+        innerClip.offset(x, y);
+
+        SkRect outerClip = { 
+            -kHalfOuterClipSize-kHalfSquareSize, -kHalfOuterClipSize-kHalfSquareSize, 
+             kHalfOuterClipSize+kHalfSquareSize,  kHalfOuterClipSize+kHalfSquareSize
+        };
+        outerClip.offset(x, y);
+
+        canvas->save();
+        canvas->clipRect(outerClip, SkRegion::kIntersect_Op);
+        canvas->clipRect(innerClip, SkRegion::kDifference_Op);
+
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setMaskFilter(createBlur())->unref();
+
+        for (int i = 0; i < 4; ++i) {
+            paint.setColor(gColors[i]);
+
+            SkRect rect = { -kHalfSquareSize, -kHalfSquareSize, kHalfSquareSize, kHalfSquareSize };
+            rect.offset(gBlurOffsets[i]);
+            rect.offset(x, y);
+            canvas->drawRect(rect, paint);
+        }
+
+        canvas->restore();
+    }
+
+    SkMaskFilter* createBlur() {
+        static const SkScalar kBlurRadius = 25.0f;
+
+        return SkBlurMaskFilter::Create(kBlurRadius,
+                                        SkBlurMaskFilter::kNormal_BlurStyle,
+                                        SkBlurMaskFilter::kHighQuality_BlurFlag);
+    }
+
+    // This draws 4 blurred shadows around a single square (centered at x, y).
+    // Each blur is offset +/- half the square's side in x & y from the original
+    // (so each blurred rect is centered at one of the corners of the original).
+    // For each blur a large outer clip is centered around the blurred rect
+    // while a difference clip stays at the location of the original rect.
+    // Each blurred rect is drawn with a draw looper where the original (non-
+    // blurred rect) is offset to reside outside of the large outer clip (so
+    // it never appears) but the offset in the draw looper is used to translate 
+    // the blurred version back into the clip.
+    void draw4x1(SkCanvas* canvas, SkScalar x, SkScalar y) {
+
+        for (int i = 0; i < 4; ++i) {
+            SkPaint loopPaint;
+
+            loopPaint.setLooper(create1Looper(-kOffsetToOutsideClip, 0, gColors[i]));
+            loopPaint.setAntiAlias(true);
+
+            SkRect outerClip = { 
+                -kHalfOuterClipSize, -kHalfOuterClipSize, 
+                kHalfOuterClipSize, kHalfOuterClipSize 
+            };
+            outerClip.offset(x, y);
+            // center it on the blurred rect
+            outerClip.offset(gBlurOffsets[i]);
+
+            SkRect rect = { -kHalfSquareSize, -kHalfSquareSize, kHalfSquareSize, kHalfSquareSize };
+            rect.offset(x, y);
+
+            canvas->save();
+                canvas->clipRect(outerClip, SkRegion::kIntersect_Op);
+                canvas->clipRect(rect, SkRegion::kDifference_Op);
+
+                // move the rect to where we want the blur to appear
+                rect.offset(gBlurOffsets[i]);
+                // then move it outside the clip (the blur stage of the draw
+                // looper will undo this translation)
+                rect.offset(SkIntToScalar(kOffsetToOutsideClip), 0);
+
+                canvas->drawRect(rect, loopPaint);
+            canvas->restore();
+        }
+    }
+
+    // Create a 1-tier drawlooper 
+    SkLayerDrawLooper* create1Looper(SkScalar xOff, SkScalar yOff, SkColor color) {
+        SkLayerDrawLooper* looper = new SkLayerDrawLooper;
+        SkLayerDrawLooper::LayerInfo info;
+
+        info.fFlagsMask = 0;
+        info.fPaintBits = SkLayerDrawLooper::kColorFilter_Bit |
+                          SkLayerDrawLooper::kMaskFilter_Bit;
+        info.fColorMode = SkXfermode::kSrc_Mode;
+        info.fOffset.set(xOff, yOff);
+        info.fPostTranslate = false;
+
+        SkPaint* paint = looper->addLayer(info);
+
+        paint->setMaskFilter(this->createBlur())->unref();
+
+        SkColorFilter* cf = SkColorFilter::CreateModeFilter(color, SkXfermode::kSrcIn_Mode);
+        paint->setColorFilter(cf)->unref();
+
+        return looper;
+    }
+
+    void draw1x4(SkCanvas* canvas, SkScalar x, SkScalar y) {
+        SkRect rect = { -kHalfSquareSize, -kHalfSquareSize, kHalfSquareSize, kHalfSquareSize };
+        rect.offset(x, y);
+
+        SkRect outerClip = { 
+            -kHalfOuterClipSize-kHalfSquareSize, -kHalfOuterClipSize-kHalfSquareSize, 
+             kHalfOuterClipSize+kHalfSquareSize,  kHalfOuterClipSize+kHalfSquareSize
+        };
+        outerClip.offset(x, y);
+
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setLooper(create4Looper(-kOffsetToOutsideClip-kHalfSquareSize, 0));
+
+        canvas->save();
+            canvas->clipRect(outerClip, SkRegion::kIntersect_Op);
+            canvas->clipRect(rect, SkRegion::kDifference_Op);
+
+            rect.offset(SkIntToScalar(kOffsetToOutsideClip+kHalfSquareSize), 0);
+            canvas->drawRect(rect, paint);
+        canvas->restore();
+    }
+
+    // Create a 4-tier draw looper
+    SkLayerDrawLooper* create4Looper(SkScalar xOff, SkScalar yOff) {
+        SkLayerDrawLooper* looper = new SkLayerDrawLooper;
+        SkLayerDrawLooper::LayerInfo info;
+
+        info.fFlagsMask = 0;
+        info.fPaintBits = SkLayerDrawLooper::kColorFilter_Bit |
+                          SkLayerDrawLooper::kMaskFilter_Bit;
+        info.fColorMode = SkXfermode::kSrc_Mode;
+        info.fPostTranslate = false;
+
+        SkPaint* paint;
+
+        for (int i = 3; i >= 0; --i) {
+            info.fOffset.set(xOff+gBlurOffsets[i].fX, yOff+gBlurOffsets[i].fY);
+            paint = looper->addLayer(info);
+
+            paint->setMaskFilter(this->createBlur())->unref();
+
+            SkColorFilter* cf = SkColorFilter::CreateModeFilter(gColors[i], SkXfermode::kSrcIn_Mode);
+            paint->setColorFilter(cf)->unref();
+        }
+
+        return looper;
+    }
+
+    typedef GM INHERITED;
+};
+
+const SkPoint MegaLooperGM::gBlurOffsets[4] = {
+    {  kHalfSquareSize,  kHalfSquareSize }, 
+    { -kHalfSquareSize,  kHalfSquareSize }, 
+    {  kHalfSquareSize, -kHalfSquareSize }, 
+    { -kHalfSquareSize, -kHalfSquareSize }
+};
+
+const SkColor MegaLooperGM::gColors[4] = {
+    SK_ColorGREEN, SK_ColorYELLOW, SK_ColorBLUE, SK_ColorRED
+};
+
+DEF_GM( return new MegaLooperGM(MegaLooperGM::k0x0_Type); )
+DEF_GM( return new MegaLooperGM(MegaLooperGM::k4x1_Type); )
+DEF_GM( return new MegaLooperGM(MegaLooperGM::k1x4_Type); )