Looking at my Firefox window today, I realized that I don't know any reasonably simple way to find out just how wide it is. I run my desktop at 1920×1200, and Firefox is hardly more than two-thirds of that width. This is actually sort of a generally-useful question.
Some quick searching around doesn't reveal any simple tools to do this for generic X11 windows… something along the lines of Xkill would be nice. I'm in Gnome, if that helps. Thanks.
Best Answer
Use xwininfo(1)