How to force an application window to be automatically maximized after starting the application?

How to startup an application (any) maximized

Starting an application via the script below, you can force any application* to startup maximized. If you either replace the main command in (a copy of-) your .desktop file by the command to run the script (see further below how to do that) or add it as a quicklist shortcut, you can achieve exactly what you want.

(* Some applications have a fixed, unchangeable windowsize, some windows open a new tab in a possibly already opened window)

About the script

The script runs with the command:

python3 /path/to/script <application>

The script:

• first runs the command to open the application
• to prevent timing issues, it then waits for the application's (new) window to appear (by finding a match between its pid and the id of the corresponding window) in the output of the wmctrl -lp -command (for only 15 seconds, to prevent an infinite loop)

• Once the window appears, it maximizes the window with the command:

  xdotool windowsize <window_id> 100% 100%
  

The code

#!/usr/bin/env python3
import subprocess
import getpass
import time
import sys

app = sys.argv[1]

user = getpass.getuser()
get = lambda x: subprocess.check_output(x).decode("utf-8")
ws1 = get(["wmctrl", "-lp"]); t = 0
subprocess.Popen(app)
while t < 30:      
    ws2 = [(w.split()[2], w.split()[0]) for w in get(["wmctrl", "-lp"]).splitlines() if not w in ws1]
    procs = sum([[(w[1], p) for p in get(["ps", "-u", user]).splitlines() \
              if app[:15].lower() in p.lower() and w[0] in p] for w in ws2], [])
    if len(procs) > 0:
        subprocess.call(["xdotool", "windowsize", "-sync", procs[0][0] , "100%", "100%"])
        break
    time.sleep(0.5)
    t = t+1

How to use

1. The script needs both wmctrl and xdotool

   sudo apt-get install wmctrl xdotool
   

2. Copy the script above into an empty file, save it as run_maximized.py

3. Now edit your .desktop file:

   • Copy the global .desktop file locally:

     cp /usr/share/applications/chromium-browser.desktop ~/.local/share/applications
     

XFCE version:

4. open the file with gedit:

   gedit ~/.local/share/applications/chromium-browser.desktop
   

   Browse to the line:

   Exec=chromium-browser %U
   

   (which is the first line, starting with Exec=

   Change it into:

   Exec=python3 /path/to/script.py chromium-browser
   

   where you need to replace /path/to/script.py by the actual path.

5. Log out and back in. From now on, your Chromium launcher will open Chromium maximized.

Unity version:

4. open the file with gedit:

   gedit ~/.local/share/applications/chromium-browser.desktop
   

   Browse to the line:

   Actions=NewWindow;Incognito;TempProfile;
   

   Change it into:

   Actions=NewWindow;Incognito;TempProfile;divider1;Open maximized;
   

   The add to the very bottom of the file the section below:

   [Desktop Action Open maximized]
   Name=Open maximized
   Exec=python3 /path/to/script.py chromium-browser
   OnlyShowIn=Unity;
   
   [Desktop Action divider1]
   Name=.....................................
   OnlyShowIn=Unity;
   

   where you need to replace /path/to/script.py by the actual path.

5. Log out and back in. From now on, your Chromium launcher looks like:

   

Important note

In a .desktop file, you must use absolute paths; ~ won't work for example. This counts for .desktop files in /usr/share/applications, ~/.local/share/applications as well as commands in Startup Applications (which are actually called by .desktop files in ~/.config/autostart).