[Ozone-DRI] Adding ScanoutBuffer interface

ui/ozone/platform/dri/scanout_buffer.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_OZONE_PLATFORM_DRI_SCANOUT_BUFFER_H_
+#define UI_OZONE_PLATFORM_DRI_SCANOUT_BUFFER_H_
+
+#include <stdint.h>
+
+#include "ui/gfx/geometry/size.h"
+#include "ui/ozone/public/native_pixmap.h"
+
+namespace ui {
+
+// Abstraction for a DRM buffer that can be scanned-out of.
+class ScanoutBuffer : public NativePixmap {

[alexst (slow to review), 2014/07/18 14:09:24]

Any particular reason you chose to inherit here? In this CL, it doesn't look
like it's used at all.

Albert is moving NativePixmap outside of ozone to be a more general purpose
object as well, btw.

[dnicoara, 2014/07/18 14:22:13]

Modifying HDC directly requires lots of other changes so I wanted to split the
change in multiple smaller CLs.

The overall idea is that:

1) HDC will take in a list of OverlayPlanes. I'll make a small change such that
OverlayPlanes carries a scoped_refptr<ScanoutBuffer>.
2) ScanoutSurface will dissapear.
3) DriSurface and DriSurfaceAdapter will meld together. They will carry 2
scoped_refptr<DriBuffer> which will be passed in to HDC on SchedulePageFlip as
the primary overlay plane.

The reasoning behind this change is: the lifetime of HDC can be shorter or
longer than that of SurfaceOzone{Canvas,EGL}. The scanout buffers need to live
until the last one of these objects is destroyed.

Let me know if anything doesn't make sense. If it makes it clearer, I can upload
the remainder of the changes as one CL.

+ public:
+  // ID allocated by the KMS API when the buffer is registered (via the handle).
+  virtual uint32_t GetFramebufferId() const = 0;
+
+  // Handle for the buffer. This is received when allocating the buffer.
+  virtual uint32_t GetHandle() const = 0;
+
+  // Size of the buffer.
+  virtual gfx::Size GetSize() const = 0;
+
+ protected:
+  virtual ~ScanoutBuffer() {}
+};
+
+class ScanoutBufferGenerator {
+ public:
+  virtual ~ScanoutBufferGenerator() {}
+
+  virtual scoped_refptr<ScanoutBuffer> Create(const gfx::Size& size) = 0;
+};
+
+}  // namespace ui
+
+#endif  // UI_OZONE_PLATFORM_DRI_SCANOUT_BUFFER_H_