Fix SkTileImageFilter clipping/cropRect interaction issue

gm/cropdisp.cpp

Index: gm/cropdisp.cpp
diff --git a/gm/cropdisp.cpp b/gm/cropdisp.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..6cc0d5fe960423582b524320acfad8232892f485
--- /dev/null
+++ b/gm/cropdisp.cpp
@@ -0,0 +1,105 @@
+/*
+ * 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 "SkBitmapSource.h"
+#include "SkColorFilter.h"
+#include "SkColorFilterImageFilter.h"
+#include "SkDisplacementMapEffect.h"
+#include "SkTileImageFilter.h"
+#include "SkXfermode.h"
+#include "gm.h"
+
+namespace skiagm {
+
+// This tests the image filter graph:
+//
+//    BitmapSource1 -- all red 512x512
+//        |
+//    ColorFilterImageFilter -- with a 64x64 crop rect - makes the pixels green
+//        |
+//    TileImageFilter -- which tiles the 64x64 green pixels across 512x512
+//        |
+//        |                BitmapSource1 -- all red 512x512
+//        | displacement   | color
+//        |                |
+//    DisplacementMapEffect -- this is only necessary to preserve the clip in the computed bounds
+//                             TileImageFilter by itself bloats the bounds to include the src
+//                             It has the TileImageFilter as the offset input.
+//
+// What was going on was that the clipRect being applied to the draw (64, 64, 512, 512)
+// was eliminating the "displacement" chain due to the crop rect.
+// This reproduces crbug/499499
+class CroppedDisplacementGM : public GM {
+public:
+    CroppedDisplacementGM() { }
+
+protected:
+
+    SkString onShortName() override {
+        return SkString("cropped-displacement");
+    }
+
+    SkISize onISize() override {
+        return SkISize::Make(kWidth, kHeight);
+    }
+
+    void onOnceBeforeDraw() override {
+        fRedBitmap.allocN32Pixels(kWidth, kHeight);
+        SkCanvas canvas(fRedBitmap);
+        canvas.clear(SK_ColorRED);
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+
+        SkPaint p;
+
+        const SkRect smRect = SkRect::MakeWH(SkIntToScalar(kSmallSize), SkIntToScalar(kSmallSize));
+        SkImageFilter::CropRect cr(smRect);
+
+        SkAutoTUnref<SkBitmapSource> bms(SkBitmapSource::Create(fRedBitmap));
+        SkAutoTUnref<SkColorFilter> cf(SkColorFilter::CreateModeFilter(SK_ColorGREEN,
+                                                                       SkXfermode::kSrc_Mode));
+        SkAutoTUnref<SkColorFilterImageFilter> cfif(SkColorFilterImageFilter::Create(cf, bms, &cr));
+
+        SkAutoTUnref<SkTileImageFilter> tif(SkTileImageFilter::Create(
+                        SkRect::MakeWH(SkIntToScalar(kSmallSize), SkIntToScalar(kSmallSize)),
+                        SkRect::MakeWH(SkIntToScalar(kWidth), SkIntToScalar(kHeight)),
+                        cfif));
+
+        static const SkScalar kScale = 20.0f;
+
+        SkAutoTUnref<SkDisplacementMapEffect> dif(SkDisplacementMapEffect::Create(
+            SkDisplacementMapEffect::kB_ChannelSelectorType,
+            SkDisplacementMapEffect::kB_ChannelSelectorType,
+            kScale,
+            tif, bms));
+
+        p.setImageFilter(dif);
+
+        canvas->clipRect(SkRect::MakeLTRB(kSmallSize+kScale/2.0f,
+                                          kSmallSize+kScale/2.0f, 
+                                          SkIntToScalar(kWidth), SkIntToScalar(kHeight)));
+        canvas->saveLayer(NULL, &p);
+        canvas->restore();
+    }
+
+private:
+    static const int kWidth = 512;
+    static const int kHeight = 512;
+    static const int kSmallSize = 64;
+
+    SkBitmap fRedBitmap;
+
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM( return SkNEW(CroppedDisplacementGM); )
+
+}