PLplot

 
> In the past I also used that kind of setup, but I don't remember to have
> such problems. I used the "packer" geometry manager, that resizes
> widgets when one of them happens to grow or shrink. What geometry
> menager are you using?

Yes, I am using "pack".  As I recall, "grid" would not work with the plplot
tk window, but I don't remember why.

> Any way, the plot window should not change size... but the appearance of
> the scroll bars could explain the reason.

Yes, it was a scroll bar issue.  I remember from a quick look that I thought
I would fix it by having the scroll bars there from the start... I just
never got around to doing it.  

Steve