ozone: Add OzoneSurface object that is owned by compositor, GLSurface

ui/gfx/ozone/surface_ozone.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_GFX_OZONE_EGL_SURFACE_OZONE_H_
+#define UI_GFX_OZONE_EGL_SURFACE_OZONE_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "skia/ext/refptr.h"
+#include "ui/gfx/gfx_export.h"
+
+class SkCanvas;
+
+namespace gfx {
+
+class Size;
+class VSyncProvider;
+
+// The platform-specific part of an EGL surface or software output.
+//
+// This class owns any bits that the ozone implementation needs freed when
+// the software output or EGL surface is destroyed.
+//
+// If you want to paint on a window with ozone, you need to create a
+// SurfaceOzone for that window.
+//
+// The platform can support software, EGL, or both for painting on the
+// window. It is not necessary to override any methods for modes the
+// platform doesn't support.
+class GFX_EXPORT SurfaceOzone {

[piman, 2014/03/27 21:20:56]

nit: can we keep SurfaceOzone a pure virtual interface, and have a
SurfaceOzoneImpl (or SurfaceOzoneBase) implement a cross-platform base for the
in-tree implementations?

This is to make sure the implementation of this doesn't become part of the
interface for out-of-tree implementations ("fragile base class problem"),
causing implicit circular dependencies.

Actually, do we even need the implementations? They're all
NOTIMPLEMENTED/NOTREACHED.

[spang, 2014/03/28 16:09:13]

I'm happy to make this a pure interface but I'd like to better understand the
reason. Can you explain further how it might create circular dependencies?

Out-of-tree platforms actually get built into the ui/ozone component, and so can
safely depend on anything ui/ozone depends on. In particular ui/gfx is allowed.
The default implementations are here only as a convenience. It would also allow
us to add more methods without necessarily breaking derived classes.

[spang, 2014/03/28 19:08:26]

Done.

+ public:
+  SurfaceOzone();
+  virtual ~SurfaceOzone();
+
+  // Initialize the surface for output using EGL/GLES2. Returns true if
+  // initialization was successful.
+  virtual bool InitializeEGL();
+
+  // Returns the EGL native window for rendering onto this surface.
+  // This can be used to to create a GLSurface.
+  virtual intptr_t /* EGLNativeWindowType */ GetEGLNativeWindow();
+
+  // Initialize canvas for software output. Returns true if initialization
+  // was successful.
+  virtual bool InitializeCanvas();
+
+  // Returns an SkCanvas for drawing on the window. The canvas is intended
+  // for use when no EGL/GLES2 acceleration is possible.
+  virtual skia::RefPtr<SkCanvas> GetCanvas();

[rjkroege, 2014/03/27 19:24:12]

if I call GetCanvas twice without an intervening PresentCanvas, what ought to
happen?

[spang, 2014/03/27 19:43:47]

I think "GetFoo" should be assumed idempotent. Therefore, calling it twice
returns the same canvas. It is not dequeuing the canvas, or anything like that.

An alternative API would be something like:

 DequeueCanvas()
 EnqueueCanvas()

That way is closer to how ANativeWindow works.

Doing that might allow some more "interesting" semantics, but we don't actually
need them for SoftwareOutputDeviceOzone, which is really the only user of this
API.

+
+  // Attempts to resize the canvas to match the viewport size. Returns true if
+  // resizing was successful, otherwise false (platforms may require a fixed
+  // size canvas). After resizing, the compositor must call GetCanvas() to get
+  // the next canvas.
+  virtual bool ResizeCanvas(const gfx::Size& viewport_size);
+
+  // Present the current canvas. After presenting, the compositor must call
+  // GetCanvas() to get the next canvas.
+  virtual bool PresentCanvas();
+
+  // Returns a gfx::VsyncProvider for this surface. Note that this may be
+  // called after we have entered the sandbox so if there are operations (e.g.
+  // opening a file descriptor providing vsync events) that must be done
+  // outside of the sandbox, they must have been completed in
+  // InitializeHardware. Returns an empty scoped_ptr on error.
+  virtual scoped_ptr<gfx::VSyncProvider> CreateVSyncProvider();
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_OZONE_SURFACE_OZONE_H_