change font but not frame size?

[David Reitter <david.reitter@gmail.com>]

Is it possible to change the font in a frame (default face) without  
changing the frame's pixel size?

`set-frame-font' has a `keep-size' argument, which would do the job,  
except that it enlarges/shrinks the frame first before bringing it  
back to the original size. That is a rather ugly effect, and when you  
try to increase font sizes gradually, or switch between different sets  
of faces in a frame, such an animation is very annoying. How can I  
avoid that?

Is there a way to block the screen update and "freeze" the frame until  
it is at its correct size?