Make RTree handle the case where the playback canvas has empty clip bounds

tests/PictureBBHTest.cpp

Index: tests/PictureBBHTest.cpp
diff --git a/tests/PictureBBHTest.cpp b/tests/PictureBBHTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..66e509b015c286ab548a8f3fd456eabebf81dbe7
--- /dev/null
+++ b/tests/PictureBBHTest.cpp
@@ -0,0 +1,112 @@
+/*
+ * 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 "SkCanvas.h"
+#include "SkBBoxHierarchy.h"
+#include "SkPaint.h"
+#include "SkPicture.h"
+#include "SkPictureRecorder.h"
+
+#include "Test.h"
+
+class PictureBBHTestBase {
+public:
+    PictureBBHTestBase(int playbackWidth, int playbackHeight,
+        int recordWidth, int recordHeight) {
+
+        fResultBitmap.allocN32Pixels(playbackWidth, playbackHeight);
+        fPictureWidth = recordWidth;
+        fPictureHeight = recordHeight;
+    }
+
+    // To clear the playback canvas at the beginning of the test
+    virtual void resetCanvas(SkCanvas& resultCanvas) = 0;

[reed1, 2014/10/29 15:56:14]

I assumed we could always assert that nothing drew, so it seems we could
eliminate the overhead of viruals for resetCanvas and validateResult, since we
just wanted to specialize on what was drawn. In that model, run() would erase to
GREEN and it could assert GREEN afterwards.

+    // To record command into the SkPicture
+    virtual void recordCommands(SkCanvas& recordingCanvas) = 0;
+    // To verify the results of playing back the SkPicture
+    virtual void validateResult(SkBitmap& playbackResult, skiatest::Reporter* reporter) = 0;
+
+    virtual ~PictureBBHTestBase() { }

[reed1, 2014/10/29 15:56:14]

nit: skia puts its destructor right after the constructor(s)

+
+    void run(skiatest::Reporter* reporter) {
+        run(NULL, reporter);
+
+        SkTileGridFactory::TileGridInfo gridInfo;
+        gridInfo.fMargin.setEmpty();
+        gridInfo.fOffset.setZero();
+        gridInfo.fTileInterval.set(1, 1);
+        SkTileGridFactory gridFactory(gridInfo);
+        run(&gridFactory, reporter);
+
+        SkRTreeFactory RTreeFactory;
+        run(&RTreeFactory, reporter);
+    }
+
+private:
+    void run(SkBBHFactory* factory, skiatest::Reporter* reporter) {
+        SkCanvas playbackCanvas(fResultBitmap);
+        resetCanvas(playbackCanvas);

[reed1, 2014/10/29 15:56:14]

nit: this->resetCanvas(...) for methods

+        SkPictureRecorder recorder;
+        SkCanvas* recordCanvas = recorder.beginRecording(fPictureWidth, fPictureHeight, factory);
+        recordCommands(*recordCanvas);
+        SkAutoTUnref<SkPicture> picture(recorder.endRecording());
+        playbackCanvas.drawPicture(picture);
+        validateResult(fResultBitmap, reporter);
+    }
+
+    SkBitmap fResultBitmap;
+    int fPictureWidth, fPictureHeight;
+};
+
+// Test to verify the playback of an empty picture
+// 
+class DrawEmptyPictureBBHTest : public PictureBBHTestBase {
+public:
+    DrawEmptyPictureBBHTest()
+        : PictureBBHTestBase(2, 2, 1, 1) { }
+
+    // Functions are all empty. Test passes by not crashing
+    virtual void resetCanvas(SkCanvas& resultCanvas) { }

[reed1, 2014/10/29 15:56:14]

nit: SK_OVERRIDE in the subclasses

+    virtual void recordCommands(SkCanvas& recordingCanvas) { }
+    virtual void validateResult(SkBitmap& playbackResult, skiatest::Reporter* reporter) { }
+    virtual ~DrawEmptyPictureBBHTest() { }
+};
+
+// Test to verify the playback of a picture into a canvas that has
+// an empty clip.
+//
+class EmptyClipPictureBBHTest : public PictureBBHTestBase {
+public:
+    EmptyClipPictureBBHTest() 
+        : PictureBBHTestBase(2, 2, 3, 3) { }
+
+    virtual void resetCanvas(SkCanvas& resultCanvas) {
+        resultCanvas.clear(SK_ColorGREEN);
+        // intersect with out of bounds rect -> empty clip.
+        resultCanvas.clipRect(SkRect::MakeXYWH(10, 10, 1, 1), SkRegion::kIntersect_Op);

[reed1, 2014/10/29 15:56:14]

seems like we can fold this clip call into the recordCommands(), eliminating the
need for this virtual entirely.

+    }
+
+    virtual void recordCommands(SkCanvas& recordingCanvas) {
+        SkPaint paint;
+        recordingCanvas.drawRect(SkRect::MakeXYWH(0, 0, 3, 3), paint);
+    }
+
+    virtual void validateResult(SkBitmap& playbackResult, skiatest::Reporter* reporter) {
+        REPORTER_ASSERT(reporter, SK_ColorGREEN == playbackResult.getColor(0, 0));
+    }
+
+    virtual ~EmptyClipPictureBBHTest() { }
+};
+
+DEF_TEST(PictureBBH, reporter) {
+
+    DrawEmptyPictureBBHTest emptyPictureTest;
+    emptyPictureTest.run(reporter);
+
+    EmptyClipPictureBBHTest emptyClipPictureTest;
+    emptyClipPictureTest.run(reporter);
+}