sdl2: add support for display rendering using opengl.

Add new sdl2-gl.c file, with display
rendering functions using opengl.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

include/ui/console.h

@@ -354,6 +354,7 @@ void surface_gl_setup_viewport(ConsoleGLState *gls,
 #endif
 
 /* sdl.c */
+void sdl_display_early_init(int opengl);
 void sdl_display_init(DisplayState *ds, int full_screen, int no_frame);
 
 /* cocoa.m */

include/ui/sdl2.h

@@ -17,6 +17,10 @@ struct sdl2_console {
     int last_vm_running; /* per console for caption reasons */
     int x, y;
     int hidden;
+    int opengl;
+    int updates;
+    SDL_GLContext winctx;
+    ConsoleGLState *gls;
 };
 
 void sdl2_window_create(struct sdl2_console *scon);
@@ -37,4 +41,11 @@ void sdl2_2d_redraw(struct sdl2_console *scon);
 bool sdl2_2d_check_format(DisplayChangeListener *dcl,
                           pixman_format_code_t format);
 
+void sdl2_gl_update(DisplayChangeListener *dcl,
+                    int x, int y, int w, int h);
+void sdl2_gl_switch(DisplayChangeListener *dcl,
+                    DisplaySurface *new_surface);
+void sdl2_gl_refresh(DisplayChangeListener *dcl);
+void sdl2_gl_redraw(struct sdl2_console *scon);
+
 #endif /* SDL2_H */