Hacking is always fun. That’s why I always lose focus on everything one interesting hack. That’s why I spent whole last night trying to figure out how to mimic Window focus event in a shell script. Though this is completely new to me, you maybe very much comfortable with implementing it :) . If so please let me know in comments.

Anyway here is my story.

I found this nice command line IM client called centerIM (Thanx @chathuraw for info). Once I got it set up I was just scanning on it’s documentation page & came across this interesting part “External actions & auto-responses“. I wrote a script right away for GUI notifications, inspired by notify.pl script for irssi. Here is the script if you are interested.

Since the load of IM messages was very high at a time & It was useless when the terminal window with centerIM was already focused (which means I’m chatting on centerIM) I was thinking of getting notifications only when centerIM window is not in focus. Few Google searches lead me to very limited resources & I chose xwininfo & xdpyinfo commands for my work.

Workaround: I’m using gnome for now & so gnome-terminal as my terminal emulator. I had to set edit > profilepreferences > Title & command option to keep initial title, in order to have “Terminal” as the terminal window name all the time.

And ran xininfo to get following output.

chanux@nim:~$ xwininfo -name Terminal

xwininfo: Window id: 0x3800003 "Terminal"

 Absolute upper-left X:  0
 Absolute upper-left Y:  52
 Relative upper-left X:  0
 Relative upper-left Y:  27
 Width: 1280
 Height: 691
 Depth: 24
 Visual Class: TrueColor
 Border width: 0
 Class: InputOutput
 Colormap: 0x20 (installed)
 Bit Gravity State: NorthWestGravity
 Window Gravity State: NorthWestGravity
 Backing Store State: NotUseful
 Save Under State: no
 Map State: IsViewable
 Override Redirect State: no
 Corners:  +0+52  -0+52  -0-25  +0-25
 -geometry 156x37+0+25

This can be used to get the window id of the windw which runs the script.

Then I can find the focused window at the moment as following.

chanux@nim:~$ xdpyinfo |grep focus
focus:  window 0x3800004, revert to Parent

I fetched the window IDs with a little bit more work.

Anyway the problem I had is that, I get 0×3800003 (at this example) or likewise for the Terminal window id & even when the Terminal id is focused I get 0×3800004 as the focused window id. Yes I know with some more work I can manage to handle that & come to a point that I can compare those window Ids to check for the focused window. But I reall like to know why that difference come up. Anyone have an explanantion? Or anyone like to mess with this?

Following is the way I fetched window ids from above outputs

chanux@nim:~$ xwininfo -name "Terminal" | grep xwininfo | cut -d " " -f 4
0x3800003
chanux@nim:~$ xdpyinfo | grep focus | cut -d " " -f 4 | sed s/,//
0x3800004