Respect window transparency when applying window shape.

ui/compositor/layer_unittest.cc

Index: ui/compositor/layer_unittest.cc
diff --git a/ui/compositor/layer_unittest.cc b/ui/compositor/layer_unittest.cc
index e44f0e4908db73e92cd666d8c0908fcd1e7f2878..c59163166c8e60a335d3166e85d02c3556ad9154 100644
--- a/ui/compositor/layer_unittest.cc
+++ b/ui/compositor/layer_unittest.cc
@@ -36,6 +36,10 @@
 #include "ui/gfx/gfx_paths.h"
 #include "ui/gfx/skia_util.h"
 
+#if defined(OS_WIN)
+#include "ui/base/win/shell.h"
+#endif
+
 using cc::MatchesPNGFile;
 
 namespace ui {
@@ -885,6 +889,77 @@ TEST_F(LayerWithRealCompositorTest, DrawPixels) {
   }
 }
 
+// Checks that using the AlphaShape filter applied to a layer with
+// transparency, alpha-blends properly with the layer below.
+TEST_F(LayerWithRealCompositorTest, DrawAlphaThresholdFilterPixels) {
+  gfx::Size viewport_size = GetCompositor()->size();
+
+  int test_size = 200;
+  EXPECT_GE(viewport_size.width(), test_size);
+  EXPECT_GE(viewport_size.height(), test_size);
+
+  int blue_height = 10;
+  // Blue with a wee bit of transparency.
+  SkColor bluish = SkColorSetARGBInline(40, 0, 0, 255);

[Wez, 2014/08/26 01:53:39]

nit: translucent_blue?

+
+  bool alpha_blend = false;

[Wez, 2014/08/26 01:53:39]

expect_alpha_blend?

[garykac, 2014/09/02 19:27:06]

Done.

+#if defined(USE_AURA) && !defined(OS_CHROMEOS)
+  alpha_blend = true;
+#if defined(OS_WIN)
+  if (!ui::win::IsAeroGlassEnabled()) {

[Wez, 2014/08/26 01:53:39]

Do we need a similar test for Linux Aura, since we won't get desktop compositing
there unless we have a suitable window manager, configuration and GPU?

+    alpha_blend = false;
+  }
+#endif  // OS_WIN
+#endif  // USE_AURA && !OS_CHROMEOS
+
+  SkColor blue_over_red;
+  if (alpha_blend) {
+    // Transparent blue blended with red.
+    blue_over_red = SkColorSetARGBInline(255, 143, 143, 183);
+  } else {
+    // Transparent blue overwriting lower layer.

[Wez, 2014/08/26 01:53:38]

This is confusingly worded.

+    blue_over_red = SkColorSetARGBInline(255, 0, 0, 40);
+  }
+
+  scoped_ptr<Layer> layer(

[Wez, 2014/08/26 01:53:39]

layer1, or background_layer

[garykac, 2014/09/02 19:27:07]

Done.

+      CreateColorLayer(SK_ColorRED, gfx::Rect(viewport_size)));
+  scoped_ptr<Layer> layer2(

[Wez, 2014/08/26 01:53:38]

or blue_layer or foreground_layer

[garykac, 2014/09/02 19:27:06]

Done.

+      CreateColorLayer(bluish, gfx::Rect(viewport_size)));
+
+  SkRegion shape;
+  shape.setRect(0, 0, viewport_size.width(), blue_height);
+  layer2->SetAlphaShape(make_scoped_ptr(new SkRegion(shape)));
+
+  layer->Add(layer2.get());
+
+  DrawTree(layer.get());
+
+  SkBitmap bitmap;
+  ASSERT_TRUE(ReadPixels(&bitmap, gfx::Rect(viewport_size)));
+  ASSERT_FALSE(bitmap.empty());
+
+  SkAutoLockPixels lock(bitmap);
+  // Ignore the edge pixels since the blending can vary on some platforms.

[Wez, 2014/08/26 01:53:39]

This only seems to ignore the top-most and left-most, not the right-most nor
bottom-most edges?

[garykac, 2014/09/02 19:27:06]

The test size is much smaller than the window, so the right/bottom edges are
already being ignored.

+  for (int x = 1; x < test_size; x++) {
+    for (int y = 1; y < test_size; y++) {
+      SkColor actual_color = bitmap.getColor(x, y);
+      SkColor expected_color = y < blue_height ? blue_over_red : SK_ColorRED;
+      EXPECT_EQ(expected_color, actual_color)
+          << "Pixel error at x=" << x << " y=" << y << "; "
+          << "actual RGBA=("
+          << SkColorGetR(actual_color) << ","
+          << SkColorGetG(actual_color) << ","
+          << SkColorGetB(actual_color) << ","
+          << SkColorGetA(actual_color) << "); "
+          << "expected RGBA=("
+          << SkColorGetR(expected_color) << ","
+          << SkColorGetG(expected_color) << ","
+          << SkColorGetB(expected_color) << ","
+          << SkColorGetA(expected_color) << ")";
+    }
+  }
+}
+
 // Checks the logic around Compositor::SetRootLayer and Layer::SetCompositor.
 TEST_F(LayerWithRealCompositorTest, SetRootLayer) {
   Compositor* compositor = GetCompositor();