glRasterPos2f moves Backbuffer?!?


I have a 2D image. I want to output text to a certain position with glRasterPos2f and glBitmap. Fortunately the text is painted on the right position in the backbuffer. Unfortunately the whole content of the backbuffer is moved when I use swapbuffers. The cause seems to be glRasterPos2f. I tried this but it doesn’t work:

VAR OldPosition:ARRAY[0..3]OF Single;
  glGetFloatv(GL_CURRENT_RASTER_POSITION,@OldPosition); //remember old RasterPos?!?
  glRasterPos2f(CharX,CharY); //Move to char position
  glBitmap(8,8,0,0,Feed,0,@CharBitmap); //Print the char
  glRasterPos3fv(@OldPosition); //Try to undo the movement

Thanks for any hint and best regards, Bernd

Ah, I saw that those coordinates differ. So glGetFloatV(GL_CURRENT_RASTER_POSITION,@OldPosition) returns window coordinates. Whereas glRasterPos will translate the given coords. Very confusing.