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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef UI_OZONE_PLATFORM_DRI_SCANOUT_SURFACE_H_
      6 #define UI_OZONE_PLATFORM_DRI_SCANOUT_SURFACE_H_
      7 
      8 #include <stdint.h>
      9 
     10 namespace gfx {
     11 class Size;
     12 }
     13 
     14 namespace ui {
     15 
     16 // ScanoutSurface is an interface for a surface that can be scanned out to a
     17 // monitor using the DRM/KMS API. Implementations will store the internal state
     18 // associated with the drawing surface. Implementations are also required to
     19 // performs all the needed operations to initialize and update the drawing
     20 // surface.
     21 //
     22 // The typical usage pattern is:
     23 // -----------------------------------------------------------------------------
     24 // HardwareDisplayController controller;
     25 // // Initialize controller
     26 //
     27 // ScanoutSurface* surface = new ScanoutSurfaceImpl(size);
     28 // surface.Initialize();
     29 // controller.BindSurfaceToController(surface);
     30 //
     31 // while (true) {
     32 //   DrawIntoSurface(surface);
     33 //   controller.SchedulePageFlip();
     34 //
     35 //   Wait for page flip event. The DRM page flip handler will call
     36 //   surface.SwapBuffers();
     37 // }
     38 //
     39 // delete surface;
     40 // -----------------------------------------------------------------------------
     41 // In the above example the wait consists of reading a DRM pageflip event from
     42 // the graphics card file descriptor. This is done by calling |drmHandleEvent|,
     43 // which will read and process the event. |drmHandleEvent| will call a callback
     44 // registered by |SchedulePageFlip| which will update the internal state.
     45 //
     46 // |SchedulePageFlip| can also be used to limit drawing to the screen's vsync
     47 // since page flips only happen on vsync. In a threaded environment a message
     48 // loop would listen on the graphics card file descriptor for an event and
     49 // |drmHandleEvent| would be called from the message loop. The event handler
     50 // would also be responsible for updating the renderer's state and signal that
     51 // it is OK to start drawing the next frame.
     52 class ScanoutSurface {
     53  public:
     54   virtual ~ScanoutSurface() {}
     55 
     56   // Used to allocate all necessary buffers for this surface. If the
     57   // initialization succeeds, the device is ready to be used for drawing
     58   // operations.
     59   // Returns true if the initialization is successful, false otherwise.
     60   virtual bool Initialize() = 0;
     61 
     62   // Swaps the back buffer with the front buffer.
     63   virtual void SwapBuffers() = 0;
     64 
     65   // Returns the ID of the current backbuffer.
     66   virtual uint32_t GetFramebufferId() const = 0;
     67 
     68   // Returns the handle of the current backbuffer.
     69   virtual uint32_t GetHandle() const = 0;
     70 
     71   // Returns the surface size.
     72   virtual gfx::Size Size() const = 0;
     73 };
     74 
     75 class ScanoutSurfaceGenerator {
     76  public:
     77   virtual ~ScanoutSurfaceGenerator() {}
     78 
     79   virtual ScanoutSurface* Create(const gfx::Size& size) = 0;
     80 };
     81 
     82 }  // namespace ui
     83 
     84 #endif  // UI_OZONE_PLATFORM_DRI_SCANOUT_SURFACE_H_
     85