This answer will use Python 3 for code examples. I encourage people to post other answers for other languages. I'll continue to update this answer, as I'm able, based on comments with tested/verified recommendations/code/etc.

Checking OS

import platform

sys = platform.system().lower()
if sys == 'linux':
    # do Linux stuff here
elif sys == 'windows':
    # do Windows stuff here
else:
    # ...

GNU+Linux

To identify which desktop environment is being used, I'm using the DESKTOP_SESSION environment variable. I get the following string values:

1. KDE/Plasma: plasma
2. Gnome: ubuntu
3. Unity: (TBD)

If there're other synonyms and/or strings for different versions of the same environment, that'd also be good to know so it can be added above.

Code:

from os import environ as env

kde = ('plasma',)
gnome = ('ubuntu',)
session = env['DESKTOP_SESSION']

if session in kde:
    # KDE/Plasma implementation here
elif session in gnome:
    # Gnome implementation here
else:
    # ...

NOTE: The GNU+Linux distro being used here is Ubuntu 22.10.

1. KDE/Plasma

Find the following file/line:

1. File: ~/.config/plasma-org.kde.plasma.desktop-appletsrc
2. Line: Image=file://<abs-path>

Note that:

1. <abs-path> is the absolute path to the file in the file system (e.g. /home/<you>/Pictures/your-wallpaper.jpg);
2. you may have multiple Image= entries (e.g. due to multiple plasma activities; I have 2 activities and 2 entries; entry 1 is for activity 1, etc.);
3. we're only grabbing the 1st entry, which is the wallpaper for the 1st activity;
4. you can look at the kscreenlockerrc file if interested in the image used by the screen locker.

Code:

from os.path import join, expanduser

wallpaper_path = None
configpath = join(
    expanduser('~'),
    '.config',
    'plasma-org.kde.plasma.desktop-appletsrc'
)
with open(configpath) as config:
    for line in config.readlines():
        if line.startswith('Image='):
            wallpaper_path = line.split('=')[1].removeprefix('file://').strip()
            break

2. Gnome

The process under Gnome boils down to the following steps:

1. Find out what the user's theme is, and
2. Use the theme-specific command to get the wallpaper path.

Theme

On a clean installation (e.g. Ubuntu 22.10), the user has the following theme options:

1. Default
2. Dark

Use this command to find out the theme currently set by the user:

gsettings get org.gnome.desktop.interface color-scheme

The possible results are below:

You can use the subprocess module for this:

theme = subprocess.run(
    'gsettings get org.gnome.desktop.interface color-scheme',
    capture_output=True,
    shell=True,
    universal_newlines=True
).stdout.strip().replace("'", '')

The returned string must have newlines and extra ' characters removed, hence the strip and replace calls.

Path

The command to get the wallpaper path is:

gsettings get org.gnome.desktop.background <key>

where <key> is one of the following theme-dependent values:

NOTE: Correct key selection depends on the result from the previous section. Using the wrong key will still give you a file system path. However, that path is not necessarily the current wallpaper (you could get lucky). In fact, the path may not even point to an existing file (e.g. running the command under KDE).

For example, if the user is using the Dark theme, then the correct command to get the path is:

gsettings get org.gnome.desktop.background picture-uri-dark

This is the reason the commands I had found hadn't been helpful, because I'm always using the dark theme, but the info/commands posted made no mention of these details.

Assuming the theme variable from the previous section, you can, again, use the subprocess module:

theme_key = 'picture-uri-dark' if theme == 'prefer-dark' else 'picture-uri'
wallpaper_path = subprocess.run(
    f'gsettings get org.gnome.desktop.background {theme_key}',
    capture_output=True,
    shell=True,
    universal_newlines=True
).stdout.strip().replace("'", '').removeprefix('file://')

3. Unity (TBD)

Microsoft

In Windows, there're at least two ways to go about this:

1. Using a PowerShell command, such as Get-ItemPropertyValue -Path "Registry::HKEY_CURRENT_USER\Control Panel\Desktop" -Name Wallpaper via the subprocess module;
2. Using the built-in winreg module, which is part of the standard library (though only available in Windows).

I'm recommending Python's winreg for the following reasons:

1. The implementation is more consistent across different versions of Windows;
2. The PowerShell command Get-ItemPropertyValue is not implemented in Windows 7;
3. It should perform better anyway, since it doesn't need to spawn a new process.

Windows 7/10

Code for Windows:

import winreg

hkey = winreg.HKEY_CURRENT_USER
subkey = 'Control Panel\\Desktop'
wallpaper_path = None
with winreg.OpenKeyEx(hkey, subkey) as regkey:          # type: PyHKEY
    value = winreg.QueryValueEx(regkey, 'Wallpaper')    # type: Tuple[str, int]
    wallpaper_path = value[0]
    try:
        with open(wallpaper_path): pass                 # see caveats below
    except Exception:
        # good luck

The structure returned by the QueryValueEx function is a tuple that looks like this:

('C:\\The\\Path To\\Your\\Wallpaper\\Image.jpg', 1)

We're interested in the first tuple element, hence value[0].

Caveats

The above code has the following version-dependent caveats:

1. Windows 7 (Python 3.7):
   1. Python 3.7 is the most recent version that will work in this Windows version, so this is how it was tested.
   2. When the user sets the wallpaper image, the OS seems to copy the file to a pre-determined location.
   3. This location seems to always remain valid, regardless of subsequent user actions.
2. Windows 10 (Python 3.11):
   1. When the user sets the wallpaper image, the OS simply stores the path to that image at the time it was set. (The OS does not seem to copy the original image to any other location like Win7 does, which is bad for us.)
   2. Subsequent user actions on the original image (e.g. rename, delete, etc) will invalidate the registry value, which still points to the original location.
   3. This implies the path returned by QueryValueEx may not even exist at the time we query for it, which means you need a fallback.
   4. We use open(wallpaper_path) as a safe way to verify the path is valid and can be accessed.
   5. The PowerShell command returns the same path as QueryValueEx, which means the PowerShell code may be using the same function internally.

Windows 11 (TBD?)

The code above might work, but I don't have Windows 11 and cannot test it here.

posted almost 2 years ago

CC BY-SA 4.0

2y ago

ghost-in-the-zsh‭

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