vcl: Use the current OpenGL context for VirtualDevice and Bitmap if possible

Conflicts:
	include/vcl/opengl/OpenGLContext.hxx
	vcl/inc/openglgdiimpl.hxx
	vcl/opengl/gdiimpl.cxx
	vcl/opengl/x11/gdiimpl.cxx
	vcl/source/opengl/OpenGLContext.cxx

Change-Id: I17f6ce66fb8b5bc027d35b4016ae56c24ee0a738

include/vcl/opengl/OpenGLContext.hxx

@@ -55,6 +55,9 @@ class NSOpenGLView;
 #include <tools/gen.hxx>
 #include <vcl/syschild.hxx>
 
+class OpenGLFramebuffer;
+class OpenGLTexture;
+
 /// Holds the information of our new child window
 struct GLWindow
 {
@@ -175,6 +178,13 @@ public:
     bool init( HDC hDC, HWND hWnd );
 #endif
 
+    // use these methods right after setting a context to make sure drawing happens
+    // in the right FBO (default one is for onscreen painting)
+    bool               AcquireDefaultFramebuffer();
+    bool               AcquireFramebuffer( OpenGLFramebuffer* pFramebuffer );
+    OpenGLFramebuffer* AcquireFramebuffer( const OpenGLTexture& rTexture );
+    void               ReleaseFramebuffer( OpenGLFramebuffer* pFramebuffer );
+
     void makeCurrent();
     void resetCurrent();
     void swapBuffers();
@@ -226,6 +236,11 @@ private:
     bool mbPixmap; // is a pixmap instead of a window
 #endif
 
+    int mnFramebufferCount;
+    OpenGLFramebuffer* mpCurrentFramebuffer;
+    OpenGLFramebuffer* mpFirstFramebuffer;
+    OpenGLFramebuffer* mpLastFramebuffer;
+
 public:
     vcl::Region maClipRegion;
     int mnPainting;