Implement blending modes for textures. Fix off-screen pixmaps to be ARGB...

Implement blending modes for textures. Fix off-screen pixmaps to be ARGB rather than RGB to enable blending across frames. Clear the screen and off-screen pixmaps when the renderer is created.

src/video/x11/SDL_x11modes.c

@@ -49,7 +49,7 @@ get_visualinfo(Display * display, int screen, XVisualInfo * vinfo)
             return 0;
         }
     }
-#ifdef SDL_VIDEO_DRIVER_X11_XRENDER
+/*#ifdef SDL_VIDEO_DRIVER_X11_XRENDER
     depth = 32;
     long vinfo_mask;
     XVisualInfo vinfo_templ;
@@ -64,7 +64,7 @@ get_visualinfo(Display * display, int screen, XVisualInfo * vinfo)
         XFree(vi);
         return 0;
     }
-#endif
+#endif*/
     depth = DefaultDepth(display, screen);
     if ((X11_UseDirectColorVisuals() &&
          XMatchVisualInfo(display, screen, depth, DirectColor, vinfo)) ||

src/video/x11/SDL_x11window.c

@@ -513,9 +513,6 @@ X11_CreateWindow(_THIS, SDL_Window * window)
     } else {
         y = window->y;
     }
-#ifdef SDL_VIDEO_DRIVER_X11_XRENDER
-    xattr.background_pixel = 0xFF000000;
-#endif
 
     w = XCreateWindow(data->display,
                       RootWindow(data->display, displaydata->screen), x, y,
@@ -526,6 +523,10 @@ X11_CreateWindow(_THIS, SDL_Window * window)
         SDL_SetError("Couldn't create window");
         return -1;
     }
+/*#ifdef SDL_VIDEO_DRIVER_X11_XRENDER
+    //XSetWindowBackground(data->display, w, 0xFF000000);
+    //XSetWindowBackgroundPixmap(data->display, w, ParentRelative);
+#endif*/
 #if SDL_VIDEO_DRIVER_PANDORA
     /* Create the GLES window surface */
     _this->gles_data->egl_surface =