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..ab867b8e587f11089ee35fa86a859a83e31f681e 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 +889,78 @@ TEST_F(LayerWithRealCompositorTest, DrawPixels) {
   }
 }
 
+// Checks that pixels are actually drawn to the screen with a read back.

[danakj, 2014/08/25 17:17:37]

This test is checking something about filters, not that pixels are drawn. Can
you make this comment about the reason this test exists?

[garykac, 2014/08/26 01:44:38]

Done.

+TEST_F(LayerWithRealCompositorTest, DrawAlphaThresholdFilterPixels) {
+  gfx::Size viewport_size = GetCompositor()->size();
+
+  // The window should be some non-trivial size but may not be exactly

[danakj, 2014/08/25 17:17:37]

drop this copy pasta

[garykac, 2014/08/26 01:44:38]

Done.

+  // 500x500 on all platforms/bots.
+  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);
+
+  bool alpha_blend = false;
+#if defined(USE_AURA) && !defined(OS_CHROMEOS)

[danakj, 2014/08/25 17:17:37]

use_aura is always true in this test file, no?

[danakj, 2014/08/25 17:17:37]

why is alpha_blend false on chromeos?

[garykac, 2014/08/26 01:44:38]

I would have loved for that to have been true, but it is not true on some of the
Windows bots.

[garykac, 2014/08/26 01:44:38]

Because the CrOS bots apparently don't alpha blend (as determined empirically).

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

[danakj, 2014/08/25 17:17:37]

what does aero glass have to do with the compositor drawing a transparent layer?

[garykac, 2014/08/26 01:44:38]

https://code.google.com/p/chromium/codesearch#chromium/src/ui/views/widget/de...

I temporarily removed the AeroGlass check to verify that it was needed here.
Sadly, the tests fail without this, so I added it back.

+    alpha_blend = false;
+  }
+#endif  // OS_WIN
+#endif  // USE_AURA && SK_SUPPORT_GPU

[danakj, 2014/08/25 17:17:37]

this comment does not match your #if

[garykac, 2014/08/26 01:44:38]

Done.

+
+  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.
+    blue_over_red = SkColorSetARGBInline(255, 0, 0, 40);
+  }
+
+  scoped_ptr<Layer> layer(
+      CreateColorLayer(SK_ColorRED, gfx::Rect(viewport_size)));
+  scoped_ptr<Layer> layer2(
+      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.
+  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();