Fold alpha to the draw in savelayer-draw-restore patterns with non-opaque draw

gm/recordopts.cpp

Index: gm/recordopts.cpp
diff --git a/gm/recordopts.cpp b/gm/recordopts.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..8c40757e8084cbe23de13716934916ece66b4715
--- /dev/null
+++ b/gm/recordopts.cpp
@@ -0,0 +1,71 @@
+/*
+ * Copyright 2014 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 "SkPath.h"
+#include "SkPictureRecorder.h"
+
+/** A call pattern that should be optimized to a single draw call. */
+static void draw_save_layer_draw_restore(SkCanvas* canvas, int layerAlpha, int drawAlpha) {
+    SkPaint layerPaint;
+    layerPaint.setColor(SkColorSetARGB(layerAlpha, 0x0, 0x00, 0x0));
+    canvas->saveLayer(NULL, &layerPaint);
+    SkPaint drawPaint;
+    drawPaint.setColor(SkColorSetARGB(drawAlpha, 100, 255, 70));
+    SkRect target(SkRect::MakeWH(SK_Scalar1, SK_Scalar1));
+    canvas->drawRect(target, drawPaint);
+    canvas->restore();
+}
+
+/**
+   Tests record optimizations. Draws shapes using a call patterns that get
+   optimized in SkRecord. Used to ensure that the optimization does not change the
+   pixels (too drasticly).
+*/
+
+class RecordOptsGM : public skiagm::GM {
+public:
+    RecordOptsGM() {
+    }
+
+protected:
+    virtual SkString onShortName() SK_OVERRIDE {
+        return SkString("recordopts");
+    }
+
+    virtual SkISize onISize() SK_OVERRIDE {
+        return SkISize::Make(256, 256);
+    }
+
+    virtual void onOnceBeforeDraw() SK_OVERRIDE {
+        SkPictureRecorder recorder;
+        SkCanvas* pictureCanvas = recorder.beginRecording(256, 256);
+        for (int layerAlpha = 0; layerAlpha < 256; ++layerAlpha) {
+            pictureCanvas->save();
+            for (int drawAlpha = 0; drawAlpha < 256; ++drawAlpha) {
+                draw_save_layer_draw_restore(pictureCanvas, layerAlpha, drawAlpha);
+                pictureCanvas->translate(SK_Scalar1, 0);
+            }
+            pictureCanvas->restore();
+            pictureCanvas->translate(0, SK_Scalar1);
+        }
+        fPicture.reset(recorder.endRecordingAsPicture());
+    }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        canvas->clear(SK_ColorTRANSPARENT);
+        fPicture->playback(canvas);

[mtklein, 2015/01/13 18:48:20]

Seems like we might also want a reference image that's drawn directly, not
through picture?

[mtklein, 2015/01/13 18:50:58]

Or even better, we can draw a diff between the non-picture and picture versions?

[Kimmo Kinnunen, 2015/01/14 13:07:51]

Done.

[Kimmo Kinnunen, 2015/01/14 13:07:51]

Done.

+    }
+
+private:
+    typedef skiagm::GM INHERITED;
+    SkAutoTUnref<SkPicture> fPicture;
+};
+
+DEF_GM( return SkNEW(RecordOptsGM); )
+