add SkCanvas::drawAtlas

gm/drawatlas.cpp

Index: gm/drawatlas.cpp
diff --git a/gm/drawatlas.cpp b/gm/drawatlas.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..89bd49c0a2cf8b530076bced84cbed7d797f5bfa
--- /dev/null
+++ b/gm/drawatlas.cpp
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2015 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 "SkRSXform.h"
+#include "SkSurface.h"
+
+class DrawAtlasGM : public skiagm::GM {
+    static SkImage* MakeAtlas(SkCanvas* caller, const SkRect& target) {
+        SkImageInfo info = SkImageInfo::MakeN32Premul(100, 100);
+        SkAutoTUnref<SkSurface> surface(caller->newSurface(info));
+        if (NULL == surface) {
+            surface.reset(SkSurface::NewRaster(info));
+        }
+        SkCanvas* canvas = surface->getCanvas();
+        // draw red everywhere, but we don't expect to see it in the draw, testing the notion
+        // that drawAtlas draws a subset-region of the atlas.
+        canvas->clear(SK_ColorRED);
+
+        SkPaint paint;
+        paint.setXfermodeMode(SkXfermode::kClear_Mode);
+        SkRect r(target);
+        r.inset(-1, -1);
+        // zero out a place (with a 1-pixel border) to land our drawing.
+        canvas->drawRect(r, paint);
+        paint.setXfermode(NULL);
+        paint.setColor(SK_ColorBLUE);
+        paint.setAntiAlias(true);
+        canvas->drawOval(target, paint);
+        return surface->newImageSnapshot();
+    }
+
+    SkAutoTUnref<SkImage> fAtlas;
+
+public:
+    DrawAtlasGM() {}
+    
+protected:
+    
+    SkString onShortName() override {
+        return SkString("draw-atlas");
+    }
+    
+    SkISize onISize() override {
+        return SkISize::Make(640, 480);
+    }
+    
+    void onDraw(SkCanvas* canvas) override {
+        const SkRect target = { 50, 50, 80, 90 };
+        if (NULL == fAtlas) {
+            fAtlas.reset(MakeAtlas(canvas, target));
+        }
+
+        const struct {
+            SkScalar fScale;
+            SkScalar fDegrees;
+            SkScalar fTx;
+            SkScalar fTy;
+            
+            void apply(SkRSXform* xform) const {
+                const SkScalar rad = SkDegreesToRadians(fDegrees);
+                xform->fSCos = fScale * SkScalarCos(rad);
+                xform->fSSin = fScale * SkScalarSin(rad);
+                xform->fTx   = fTx;
+                xform->fTy   = fTy;
+            }
+        } rec[] = {
+            { 1, 0, 10, 10 },       // just translate
+            { 2, 0, 110, 10 },      // scale + translate
+            { 1, 30, 210, 10 },     // rotate + translate
+            { 2, -30, 310, 30 },    // scale + rotate + translate
+        };
+
+        const int N = SK_ARRAY_COUNT(rec);
+        SkRSXform xform[N];
+        SkRect tex[N];
+        SkColor colors[N];
+
+        for (int i = 0; i < N; ++i) {
+            rec[i].apply(&xform[i]);
+            tex[i] = target;
+            colors[i] = 0x80FF0000 + (i * 40 * 256);
+        }
+
+        SkPaint paint;
+        paint.setFilterQuality(kLow_SkFilterQuality);
+        paint.setAntiAlias(true);
+
+        canvas->drawAtlas(fAtlas, xform, tex, N, NULL, &paint);
+        canvas->translate(0, 100);
+        canvas->drawAtlas(fAtlas, xform, tex, colors, N, SkXfermode::kSrcIn_Mode, NULL, &paint);
+    }
+    
+private:
+    typedef GM INHERITED;
+};
+DEF_GM( return new DrawAtlasGM; )
+