Implemented offscreen rendering path for GLES2CmdDecoder on Linux....

gpu/command_buffer/service/x_utils.h

Index: gpu/command_buffer/service/x_utils.h
===================================================================
--- gpu/command_buffer/service/x_utils.h	(revision 43138)
+++ gpu/command_buffer/service/x_utils.h	(working copy)
@@ -13,36 +13,97 @@
 
 namespace gpu {
 
+// Abstracts between on-screen and off-screen GLX contexts.
+class GLXContextWrapper {
+ public:
+  explicit GLXContextWrapper(Display* display)
+      : display_(display),
+        context_(NULL) {
+    DCHECK(display_);
+  }
+
+  virtual ~GLXContextWrapper();
+
+  // Initializes the GL context. Subclasses should perform their
+  // initialization work and then call the superclass implementation.
+  virtual bool Initialize();
+
+  // Destroys the GL context. Subclasses may call this before or after
+  // doing any necessary cleanup work.
+  virtual void Destroy();
+
+  // Makes the GL context current on the current thread.
+  virtual bool MakeCurrent() = 0;
+
+  // Returns true if this context is offscreen.
+  virtual bool IsOffscreen() = 0;
+
+  // Swaps front and back buffers. This has no effect for off-screen
+  // contexts.
+  virtual void SwapBuffers() = 0;
+
+  // Fetches the GLX context for sharing of server-side objects.
+  GLXContext GetContext() {
+    return context_;
+  }
+
+ protected:
+  Display* GetDisplay() {
+    return display_;
+  }
+
+  void SetContext(GLXContext context) {
+    context_ = context;
+  }
+
+ private:
+  Display* display_;
+  GLXContext context_;
+
+  DISALLOW_COPY_AND_ASSIGN(GLXContextWrapper);
+};
+
 // This class is a wrapper around an X Window and associated GL context. It is
 // useful to isolate intrusive X headers, since it can be forward declared
 // (Window and GLXContext can't).
-class XWindowWrapper {
+class XWindowWrapper : public GLXContextWrapper {
  public:
   XWindowWrapper(Display *display, Window window)
-      : display_(display),
+      : GLXContextWrapper(display),
         window_(window) {
-    DCHECK(display_);
     DCHECK(window_);
   }
-  // Initializes the GL context.
-  bool Initialize();
 
-  // Destroys the GL context.
-  void Destroy();
+  virtual bool Initialize();
+  virtual bool MakeCurrent();
+  virtual bool IsOffscreen();
+  virtual void SwapBuffers();
 
-  // Makes the GL context current on the current thread.
-  bool MakeCurrent();
-
-  // Swaps front and back buffers.
-  void SwapBuffers();
-
  private:
-  Display *display_;
   Window window_;
-  GLXContext context_;
   DISALLOW_COPY_AND_ASSIGN(XWindowWrapper);
 };
 
+// This class is a wrapper around a GLX pbuffer and associated GL context. It
+// serves the same purpose as the XWindowWrapper for initializing off-screen
+// rendering.
+class GLXPbufferWrapper : public GLXContextWrapper {
+ public:
+  explicit GLXPbufferWrapper(Display* display)
+      : GLXContextWrapper(display) {
+  }
+
+  virtual bool Initialize();
+  virtual void Destroy();
+  virtual bool MakeCurrent();
+  virtual bool IsOffscreen();
+  virtual void SwapBuffers();
+
+ private:
+  GLXPbuffer pbuffer_;
+  DISALLOW_COPY_AND_ASSIGN(GLXPbufferWrapper);
+};
+
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_X_UTILS_H_