Use xdg-desktop-portal for Image.grab() on Linux

Making a Screenshot on Linux is little bit hacky. Especially on Wayland. @radarhere tried to solve the problem in #6312 by using gnome-screenshot, but this is not a good way. It works only on Systems with Gnome. Of course, you can also add other Screenshot tools but it is far more hacky and it will not work in Sandboxed Environments. Luckily there is a Better Way: There is a official D-Bus API for taking Screenshots. It works in every Desktop Environment in X11 and Wayland. It works also in Sandboxed and Unsandboxed Environments. Here is a Example code that uses it:

import dbus
import dbus.mainloop.glib
from dbus.mainloop.glib import DBusGMainLoop

from gi.repository import GLib


def testresp(response, results, object_path):
    print(results["uri"])


def main():
    loop = GLib.MainLoop()
    dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)
    bus = dbus.SessionBus()
    obj = bus.get_object("org.freedesktop.portal.Desktop", "/org/freedesktop/portal/desktop")
    inter = dbus.Interface(obj, "org.freedesktop.portal.Screenshot")
    bus.add_signal_receiver(
        testresp,
        signal_name="Response",
        dbus_interface="org.freedesktop.portal.Request",
        bus_name="org.freedesktop.portal.Desktop",
        path_keyword="object_path")
    inter.Screenshot("", {})
    loop.run()


main()

It needs the dbus-python. This Lib might not be the best choice, since it might be tricky to install and the mainloop can cause problems.

You can also use this API with the Shell:

gdbus call --session --dest org.freedesktop.portal.Desktop --object-path /org/freedesktop/portal/desktop --method org.freedesktop.portal.Screenshot.Screenshot "" {}

This makes a Screenshot, but I haven't found a Way to get the response, so the Program don't know where the Screenshot has been saved.

This Issue is a note that this API exists. If someone reading this with a better knowledge of D-Bus, he or she can write a better code in a more sustainable lib and make a PR. I might also take a closer look at this when I have some free time.

Start at the Image.grab() entry point and read the xdg-desktop-portal Screenshot API linked in the issue. Evaluate a sustainable D-Bus approach and its response handling; done means Linux screenshots work across X11 and Wayland, including sandboxed and unsandboxed environments, with the saved location available to the program.