Add support for GNOME in dom0/GUI domain

[marmarek]

Tasks here:

• window decoration (colorful frames)
• stripping unneeded components (file manager, automounting devices etc)
• adjusting application menu
• Qubes Manager integration (whatever it means)

[tasket]

Has there been any open discussion of the need/desire for this?

[bnvk]

@ttasket yes, there has been some discussion on the mailing lists, but ultimately it was a decision of core team to work towards this!

[woju]

Results of a preliminary research:

• GTK+3 prefers client-side decorations (CSD), though it still draws decorations around windows which don't draw them the GTK+ way; the code used is the same, CSS based, but done by the window manager (Mutter)
• one general problem with GTK is that some applications want to customise their headerbars (they add some buttons); the result is two sets of decorations; we probably can design our decorations to just include thin border (like in "Activities" gnome-shell panel) and a label with domain name
• based on comment by someone on one of the gnome-related IRC channels, it's currently not possible to do it in Mutter without patching
• we control both the client and server side (the window belongs to gui-daemon and we can supply an extension to gnome shell)
• @marmarek doesn't want to convert gui-daemon into GTK+ application, because:
  • there are some problems foreseen (something around event ordering, which I didn't understand
  • he would have to do it
• playing around gnome shell JS console proved unsuccesful (the guy on IRC was probably right)
• the following code is an example of styling window decoration; instantiation of Gtk.HeaderBar seems to be mandatory, if not created, the decorations are drawn by Mutter at least in 3.10 (Debian 8)
• messing around style providers to write custom implementation in Python (to generate dynamic colours, because labels may be changed) was also fruitless, because they use private interfaces and the public, documented interfaces don't really work

#!/usr/bin/env python3

import pdb
import gi
from gi.repository import Gdk, Gtk

def get_css():
    return ''.join(
        '''
        .qubes-label-{name} .header-bar,
        .qubes-label-{name} .titlebar,
        .qubes-label-{name}
        {{
            background: dark{name};
        }}
        '''.format(name=name)
        for name in ('red', 'green', 'blue')).encode('ascii')

def main():
    provider = Gtk.CssProvider()
    provider.load_from_data(get_css())
#   provider.load_from_file(FILENAME)

    Gtk.StyleContext.add_provider_for_screen(
        Gdk.Screen.get_default(),
        provider,
        Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION
    )

    win = Gtk.Window(title='titlebar')
    win.get_style_context().add_class('qubes-label-blue')

    header_bar = Gtk.HeaderBar()
    header_bar.set_title('header-bar')
    header_bar.set_subtitle('dom0')
    header_bar.set_show_close_button(True)
    win.set_titlebar(header_bar)

    button = Gtk.Button(label='Break to PDB')
    def on_clicked(widget, win=win): #, header_bar=header_bar):
        try:
            pdb.set_trace()
        except bdb.BdbQuit:
            Gtk.main_quit(widget)
    button.connect('clicked', on_clicked)
    win.add(button)

    win.connect('delete-event', Gtk.main_quit)
    win.show_all()
    Gtk.main()

if __name__ == '__main__':
    main()

# vim: ts=4 sts=4 sw=4 et

[woju]

Oh, and forgot to add: there are two programs which aid debugging GTK+ applications: GTK+ Inspector (>= gtk 3.14) and gtkparasite (for older, like 3.10 in jessie).

[mfc]

from my understanding of the warsaw meetings, @bnvk is no longer attempting to implement this anymore, so I removing it from being assigned to him. I am assigning a help wanted label as well.