REsize window question

[Stéphane RIFF]

My mapserver application need to redraw the map when the window is resized.
My problem is that i don't know how to keep the same extent
in two map with different size !!! in fact i don't want the map
to change its scale when i resize the window.
How can i calculate the newExtent to do that ???
Is it possible ???
How do you handle that kind of function ? example ?

Thanks