Gnome Dynamic Icon

[ycar]

Hi,
The following is just an idea about how to dynamically modify an icon on Gnome Desktop.
The below steps describe a technique used to make an icon to show the minute last digit.
(Ex: if the current time is 18:03, then an icon on the desktop shows image '3' - see attached image).
This has no useful meaning, but the idea can be used in other applications where an icon should be dynamically changed.

1. Background
The GNOME Icon file (*.desktop) has a format similar to the below one:
#!/usr/bin/env xdg-open
[Desktop Entry]
Encoding=UTF-8
Exec=firefox %u
Icon=firefox
Name=Firefox
...
Where "Icon" tag points to a png file in /usr/share/pixmaps (without specifying the extension *.png).
And "Name" tag is the title displayed below the icon.
The idea is to dynamically modify these two parameters in an Icon file (to dynamically change the image and title).

2. Create [0-9].png images
2.1 Create 10 images (48x48/png) with names 0.png, 1.png, 2.png... 9.png; representing numbers from 0 to 9 (each image has a picture of its number).
2.2 Copy all 10 images to /usr/share/pixmaps/

3. Create template icon
3.1 Create $HOME/Temp/0.desktop with the following content (the icon will be used as a template for desktop icon instances):
#!/usr/bin/env xdg-open
[Desktop Entry]
Encoding=UTF-8
Icon=0
Name=0

4. Create script for generating desktop icon instances
4.1 Create the following script in $/HOME/bin/track_mins.sh (which will generate icon insatnces, based on current time and icon template):
#!/bin/sh
# Get minutes last digit
MIN_LAST_DIG=`date '+%M' | sed 's/.//'`
# Generate a new icon instance (based on icon template and copy it to the desktop, replacing the old instance)
sed -e "s/Icon=[0-9]/Icon=${MIN_LAST_DIG}/" \
-e "s/Name=[0-9]/Name=${MIN_LAST_DIG}/" \
$HOME/Temp/0.desktop > $HOME/Desktop/min.desktop

5. Modify CRONTAB file
5.1 Modify crontab file to include the above script to be executed every minute.
$ crontab -e
5.2 Add the following line to crontab file:
* * * * * $HOME/bin/track_mins.sh

Done :).
Thanks! (+ sorry for my english :) )

[jpeddicord]

Interesting idea. Approved, thank you for your tutorials & tips contribution.

Also, going to throw this out there: instead of modifying the .desktop entry directly for the new icon, it is also possible to point the Icon line to a symlink. You could then change the symlink in the cron script to point to the corresponding icons. Just a thought. :)

Jacob

[ycar]

Thanks Jacob,
Indeed, for some applications a better solution is to use simlink (point to a different *.desktop files already predefined).
However, my point was to show that *.desktop files could be modified dynamically and this is easy to implement with script+sed+cron. There could be applications where this is the only one solution (let's say you want to dynamically change Icon title) :).
Thanks.