Mac Overlays: Wire up overlays on Mac

ui/gl/gl_image_io_surface.mm

Index: ui/gl/gl_image_io_surface.mm
diff --git a/ui/gl/gl_image_io_surface.cc b/ui/gl/gl_image_io_surface.mm
similarity index 88%
rename from ui/gl/gl_image_io_surface.cc
rename to ui/gl/gl_image_io_surface.mm
index adcadee363ab5499ca14bd43fbf5bff11378ba51..ea6aac2de856cf0eee6514ec1988d1c4a3cd5acf 100644
--- a/ui/gl/gl_image_io_surface.cc
+++ b/ui/gl/gl_image_io_surface.mm
@@ -4,10 +4,12 @@
 
 #include "ui/gl/gl_image_io_surface.h"
 
+#include "base/mac/foundation_util.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_context.h"
 
 // Note that this must be included after gl_bindings.h to avoid conflicts.
+#include <Quartz/Quartz.h>
 #include <OpenGL/CGLIOSurface.h>
 
 namespace gfx {
@@ -192,7 +194,20 @@ bool GLImageIOSurface::ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                             OverlayTransform transform,
                                             const Rect& bounds_rect,
                                             const RectF& crop_rect) {
-  return false;
+  // Only simple overlay planes are currently supported.
+  DCHECK_EQ(z_order, 0);
+  DCHECK_EQ(crop_rect.ToString(), gfx::RectF(0, 0, 1, 1).ToString());
+  DCHECK_EQ(transform, gfx::OVERLAY_TRANSFORM_NONE);
+
+  // Note that gfx::AcceleratedWidget does not actually map to CALayer in this
+  // context. It may be that the types should coincide.
+  CALayer* layer = base::mac::ObjCCastStrict<CALayer>(widget);

[alexst (slow to review), 2015/07/22 14:38:02]

In the type definitions 

#elif defined(OS_MACOSX)
typedef NSView* AcceleratedWidget;
...

If I understand correctly, you are using the widget as a transport type to pass
the layer into the image. Are CALayer and NSView related? Is it safe to cast
them around like that?

The way we use it on ozone and the way I thought of it conceptually is that you
are presenting the contents of an image as an overlay for the compositor whose
backing surface is represented by |widget|. If the types (per above) are
compatible and CALayer looks like it is indeed a form of backing surface, I
think this is fine. Otherwise, maybe you could just have a maps of widget ->
layer to resolve type safety.

[ccameron, 2015/07/23 05:33:02]

I'm not sure if we actually use NSView as a type anywhere. In the browser
process, we use a phony NSView* and a map to internal structures here:
https://code.google.com/p/chromium/codesearch#chromium/src/ui/accelerated_wid...

As it is, I'm essentially treating it as a void*, with some casts.

+
+  // Also note that transactions are not disabled. The caller must ensure that
+  // all changes to the CALayer tree happen atomically.
+  [layer setContents:(id)io_surface_.get()];
+  [layer setFrame:bounds_rect.ToCGRect()];
+  return true;
 }
 
 }  // namespace gfx