Specifying X windows' geometry in the coordinates obtained from wmctrl

The --geometry option for gnome-terminal is actually measured in characters, rather than pixels. For example, to get an 80 column terminal only 10 lines high, you can launch gnome-terminal like this:

gnome-terminal --geometry 80x10

The terminal will resize in increments of the font character size, which it communicates to the Xserver using WM_NORMAL_HINTS. You can examine these using the xprop command. For example, here I find a Terminal window id, and ask xprop about it:

$ wmctrl -lG | tail -n1
0x06400021  0 592  314  580  338  myhostname kees@myhostname: ~
$ xprop -id 0x6400021
...
WM_NORMAL_HINTS(WM_SIZE_HINTS):
        program specified minimum size: 48 by 16
        program specified resize increment: 7 by 14
        program specified base size: 20 by 2
        window gravity: NorthWest
...

In the above case, the font size is 7 by 14 pixels. So if I wanted a 70 by 140 pixel Terminal, I could run gnome-terminal --geometry 10x10 (though it would be 20 x 2 pixels larger than that based on the window manager decorations, etc, as seen in the "specific base size" above).