center_active_window.py

#!/usr/bin/env python3

# Author: Serg Kolo
# Date: Oct 3rd, 2016
# Description: Script for aligning the center of 
#     user's active window with the center of the monitor
# Tested on: Ubuntu 16.04
# Written for: http://askubuntu.com/q/832720/295286
from __future__ import print_function
import gi
gi.require_version('Gdk','3.0')
from gi.repository import Gdk
import subprocess

def get_offset(*args):
    command = ['xprop','-notype','_NET_FRAME_EXTENTS',
               '-id',str(args[0])
    ]

    out = subprocess.check_output(command)
    if 'not found' in out.decode():
        return 0
    return int(out.decode().strip().split(',')[-2])

def main():

    screen = Gdk.Screen.get_default()
    window = screen.get_active_window()
    window.unmaximize()
    window_width = window.get_width()
    window_y = window.get_origin()[-1]
    print(window_y)
    window_monitor = screen.get_monitor_at_window(window)
    mon_g = screen.get_monitor_geometry(window_monitor)
    print(mon_g.width,mon_g.height)
    monitor_center = screen.get_monitor_geometry(window_monitor).width/2

    # if centers of window and screen are aligned
    # the top left corner will be at screen_center - window_width/2    
    new_position = monitor_center - window_width /2

    # For some reason there is vertical offset necessary
    # Apparently this comes form _NET_FRAME_EXTENTS value
    offset = get_offset(int(window.get_xid()))

    window.move(new_position,window_y-offset)
    print(window.get_origin()) 

if __name__ == '__main__':
    main()

Please add
import gi
gi.require_version('Gdk', '3.0')
before
from gi.repository import Gdk
...to avoid warning under Ubuntu 17.04. It does otherwise work great. Thank you! :)

On Ubuntu 19.10 have error:

Traceback (most recent call last): File "/bin/center-active-window.py", line 45, in <module> main() File "/bin/center-active-window.py", line 39, in main offset = get_offset(int(window.get_xid())) File "/bin/center-active-window.py", line 20, in get_offset return int(out.decode().strip().split(',')[-2]) IndexError: list index out of range

And some warnings:
/bin/center-active-window.py:11: PyGIWarning: Gdk was imported without specifying a version first. Use gi.require_version('Gdk', '3.0') before import to ensure that the right version gets loaded. from gi.repository import Gdk /bin/center-active-window.py:25: DeprecationWarning: Gdk.Screen.get_active_window is deprecated window = screen.get_active_window() 280 /bin/center-active-window.py:30: DeprecationWarning: Gdk.Screen.get_monitor_at_window is deprecated window_monitor = screen.get_monitor_at_window(window) /bin/center-active-window.py:31: DeprecationWarning: Gdk.Screen.get_monitor_geometry is deprecated monitor_center = screen.get_monitor_geometry(window_monitor).width/2

Plz, fix it ;)

@Kvols Sorry for delayed reply . . .very delayed. This is fixed.

@dmyTRUEk Fixed, the error happens because Ubuntu 19.10 uses GNOME, and GNOME for some reason doesn't set _NET_FRAME_EXTENTS property anymore. So xprop fails and returns error in the output. There's a few other problems that I found with this script (for example y centering doesnt work well and panned display needs to be accounted for, even though this is rare nowadays), so I'll try to fix them some time this month and account for couple other X11 properties. Remind me maybe like in January if you don't see any updates on this.

Hello @SergKolo,

Thank you for the script! In order to make it work for my setup using two monitors, I had to modify it a little bit.
Basically, I had to write monitor_center = mon_g.x + mon_g.width/2 in order to make take into account where the monitor begins.

I also modified it a bit for centralising in both x and y. I will put in here in case someone find it useful.

def main():

    screen = Gdk.Screen.get_default()
    window = screen.get_active_window()
    window.unmaximize()
    window_width = window.get_width()
    window_height = window.get_height()
    
    window_monitor = screen.get_monitor_at_window(window)
    mon_g = screen.get_monitor_geometry(window_monitor)
    print(mon_g.width,mon_g.height)
    monitor_center_x = mon_g.x + mon_g.width/2
    monitor_center_y = mon_g.y + mon_g.height/2

    # if centers of window and screen are aligned
    new_position_x = monitor_center_x - window_width /2
    new_position_y = monitor_center_y - window_height /2

    window.move(new_position_x,new_position_y)
    print(window.get_origin()) 

@orlandini Thank you for contributing what worked for your setup. Just a question, what desktop environment do you use and do you use any docks/panels ?

Hi @SergKolo. I am Ubuntu 18.04 with GNOME 3.28.2. I am mostly using the default settings. To be honest, I have not used linux systems for quite a while, so if there are any other relevant settings, please let me know.

Thanks for the script. It works fine under Ubuntu 20.04 apart from the height isn't maintained. For example if I align a window to one side of the screen and then the height is 100%. When centering the window then the height becomes smaller.

Thank you for this script! Working on Manjaro.

@orlandini works well on dual monitors here inside ubuntu 20.04. Thanks! the original script will always center on the 'primary' monitor instead of my 'active'(i.e. the monitor I current am using) monitor.

I want to thank both of you who created/contributed to this script. The original works for one monitor, and the modified version for however many. Good find. Thank you both.