UpdateRect on X11 in Window Mode?

Hey. I do not know, wether this is a bug or not, but if I do run an SDL
Programm (SDLv1.1.5) under X11, there is no use of using any update
sequence, because everything I draw on the SDL_Surface will be directly
drawn to the window. The following things I tested on this:

  • it happens under X11 with a window-manager (tested on KDE, KDE2,
  • it doesn’t happen, if i switch to SDL_FULLSCREEN
  • its independend, if I use SDL_SWSURFACE or SDL_HWSURFACE
  • it has nothing to do with SDL_DOUBLEBUFF
  • The use of SDL_ANYSURFACE doesn’t help either

Might it be a bug, or must it be like this ?