Support removal of DRI platform

ui/gfx/ozone/impl/dri_surface.h

-// Copyright 2013 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_IMPL_DRI_SURFACE_H_
-#define UI_GFX_OZONE_IMPL_DRI_SURFACE_H_
-
-#include "base/compiler_specific.h"
-#include "base/memory/scoped_ptr.h"
-#include "ui/gfx/skia_util.h"
-
-class SkBitmapDevice;
-class SkCanvas;
-
-namespace gfx {
-
-class DriSkBitmap;
-class HardwareDisplayController;
-
-// DriSurface is used to represent a surface that can be scanned out
-// to a monitor. It will store the internal state associated with the drawing
-// surface associated with it. DriSurface also performs all the needed
-// operations to initialize and update the drawing surface.
-//
-// The implementation uses dumb buffers, which is used for software rendering.
-// The intent is to have one DriSurface implementation for a
-// HardwareDisplayController.
-//
-// DoubleBufferedSurface is intended to be the software analog to
-// EGLNativeSurface while DriSurface is intended to provide the glue
-// necessary to initialize and display the surface to the screen.
-//
-// The typical usage pattern is:
-// -----------------------------------------------------------------------------
-// HardwareDisplayController controller;
-// // Initialize controller
-//
-// DriSurface* surface = new DriSurface(controller);
-// surface.Initialize();
-// controller.BindSurfaceToController(surface);
-//
-// while (true) {
-//   SkCanvas* canvas = surface->GetDrawableForWidget();
-//   DrawStuff(canvas);
-//   controller.SchedulePageFlip();
-//
-//   Wait for page flip event. The DRM page flip handler will call
-//   surface.SwapBuffers();
-// }
-//
-// delete surface;
-// -----------------------------------------------------------------------------
-// In the above example the wait consists of reading a DRM pageflip event from
-// the graphics card file descriptor. This is done by calling |drmHandleEvent|,
-// which will read and process the event. |drmHandleEvent| will call a callback
-// registered by |SchedulePageFlip| which will update the internal state.
-//
-// |SchedulePageFlip| can also be used to limit drawing to the screen's vsync
-// since page flips only happen on vsync. In a threaded environment a message
-// loop would listen on the graphics card file descriptor for an event and
-// |drmHandleEvent| would be called from the message loop. The event handler
-// would also be responsible for updating the renderer's state and signal that
-// it is OK to start drawing the next frame.
-//
-// The following example will illustrate the system state transitions in one
-// iteration of the above loop.
-//
-// 1. Both buffers contain the same image with b[0] being the front buffer
-// (star will represent the frontbuffer).
-// -------  -------
-// |     |  |     |
-// |     |  |     |
-// |     |  |     |
-// |     |  |     |
-// -------  -------
-// b[0]*    b[1]
-//
-// 2. Call |GetBackbuffer| to get a SkCanvas wrapper for the backbuffer and draw
-// to it.
-// -------  -------
-// |     |  |     |
-// |     |  |  d  |
-// |     |  |     |
-// |     |  |     |
-// -------  -------
-// b[0]*    b[1]
-//
-// 3. Call |SchedulePageFlip| to display the backbuffer. At this point we can't
-// modify b[0] because it is the frontbuffer and we can't modify b[1] since it
-// has been scheduled for pageflip. If we do draw in b[1] it is possible that
-// the pageflip and draw happen at the same time and we could get tearing.
-//
-// 4. The pageflip callback is called which will call |SwapSurfaces|. Before
-// |SwapSurfaces| is called the state is as following from the hardware's
-// perspective:
-// -------  -------
-// |     |  |     |
-// |     |  |  d  |
-// |     |  |     |
-// |     |  |     |
-// -------  -------
-// b[0]     b[1]*
-//
-// 5. |SwapSurfaces| will update out internal reference to the front buffer and
-// synchronize the damaged area such that both buffers are identical. The
-// damaged area is used from the SkCanvas clip.
-// -------  -------
-// |     |  |     |
-// |  d  |  |  d  |
-// |     |  |     |
-// |     |  |     |
-// -------  -------
-// b[0]     b[1]*
-//
-// The synchronization consists of copying the damaged area from the frontbuffer
-// to the backbuffer.
-//
-// At this point we're back to step 1 and can start a new draw iteration.
-class DriSurface {
- public:
-  DriSurface(HardwareDisplayController* controller);
-
-  virtual ~DriSurface();
-
-  // Used to allocate all necessary buffers for this surface. If the
-  // initialization succeeds, the device is ready to be used for drawing
-  // operations.
-  // Returns true if the initialization is successful, false otherwise.
-  bool Initialize();
-
-  // Returns the ID of the current backbuffer.
-  uint32_t GetFramebufferId() const;
-
-  // Synchronizes and swaps the back buffer with the front buffer.
-  void SwapBuffers();
-
-  // Get a Skia canvas for a backbuffer.
-  SkCanvas* GetDrawableForWidget();
-
- private:
-  friend class HardwareDisplayController;
-
-  // Used to create the backing buffers.
-  virtual DriSkBitmap* CreateBuffer();
-
-  // Stores DRM information for this output device (connector, encoder, last
-  // CRTC state).
-  HardwareDisplayController* controller_;
-
-  // The actual buffers used for painting.
-  scoped_ptr<DriSkBitmap> bitmaps_[2];
-
-  // BitmapDevice for the current backbuffer.
-  skia::RefPtr<SkBitmapDevice> skia_device_;
-
-  // Canvas for the current backbuffer.
-  skia::RefPtr<SkCanvas> skia_canvas_;
-
-  // Keeps track of which bitmap is |buffers_| is the frontbuffer.
-  int front_buffer_;
-
-  DISALLOW_COPY_AND_ASSIGN(DriSurface);
-};
-
-}  // namespace gfx
-
-#endif  // UI_GFX_OZONE_IMPL_DRI_SURFACE_H_