Example GTK to create a dock-like bar and strut

dockbar-gtk2.py

#!/usr/bin/env python2
#
# dockbar.py
#
# Example program places a coloured bar across the top of the
# current monitor
#
# demonstrates
#
# (a) creating the bar as an undecorated "dock" window   
# (b) setting its colour
# (c) getting the number of monitors and their sizes
#
#                                                         JL 20140512

import gtk

# Colour style for (b)
colour_rc= """
style "bar-colour" {
    bg[NORMAL] = "Dark Red"
} widget "*bar" style "bar-colour"
"""

#  the size of the bar (its height), in pixels
bar_size = 10

def main ():

    # (a) Create an undecorated dock
    window = gtk.Window()
    window.set_name("bar")
    window.set_type_hint(gtk.gdk.WINDOW_TYPE_HINT_DOCK)
    window.set_decorated(False)
    window.connect("destroy", gtk.main_quit)

    # (b) Style it
    gtk.rc_parse_string(colour_rc)

    # the screen contains all monitors
    screen = window.get_screen()
    width = gtk.gdk.screen_width()
    print "width: %d" % width

    # (c) collect data about each monitor
    monitors = []
    nmons = screen.get_n_monitors()
    print "there are %d monitors" % nmons
    for m in range(nmons):
      mg = screen.get_monitor_geometry(m)
      width = mg.width
      print "monitor %d: %d x %d" % (m,mg.width,mg.height)
      monitors.append(mg)

    # current monitor
    curmon = screen.get_monitor_at_window(screen.get_active_window())
    x, y, width, height = monitors[curmon]
    print "monitor %d: %d x %d (current)" % (curmon,width,height)
    print "bar: start=%d end=%d" % (x,x+width-1)

    # display bar along the top of the current monitor
    window.move(x,y)
    window.resize(width,bar_size)

    # it must be shown before changing properties 
    window.show_all()

    # (d) reserve space (a "strut") for the bar so it does not become obscured
    #     when other windows are maximized, etc
    topw = window.get_toplevel().window
    topw.property_change("_NET_WM_STRUT","CARDINAL",32,gtk.gdk.PROP_MODE_REPLACE,
            [0, 0, bar_size, 0])
    topw.property_change("_NET_WM_STRUT_PARTIAL","CARDINAL",32,gtk.gdk.PROP_MODE_REPLACE,
            [0, 0, bar_size, 0, 0, 0, 0, 0, x, x+width-1, 0, 0])


    # we set _NET_WM_STRUT, the older mechanism as well as _NET_WM_STRUT_PARTIAL
    # but window managers ignore the former if they support the latter.
    #
    # the numbers in the array are as follows:
    #
    # 0, 0, bar_size, 0 are the number of pixels to reserve along each edge of the
    # screen given in the order left, right, top, bottom. Here the size of the bar
    # is reserved at the top of the screen and the other edges are left alone.
    #
    # _NET_WM_STRUT_PARTIAL also supplies a further four pairs, each being a
    # start and end position for the strut (they don't need to occupy the entire
    # edge).
    #
    # In the example, we set the top start to the current monitor's x co-ordinate
    # and the top-end to the same value plus that monitor's width, deducting 1,
    # because the xo-ordinate system starts at 0 rather than 1. The net result
    # is that space is reserved only on the current monitor.
    #
    # co-ordinates are specified relative to the screen (i.e. all monitors together).
    #


    # main event loop
    gtk.main()

if __name__ == "__main__":
    main ()

dockbar-gtk3.py

#!/usr/bin/env python
#
# dockbar.py
#
# Example program places a coloured bar across the top of the
# current monitor
#
# demonstrates
#
# (a) creating the bar as an undecorated "dock" window   
# (b) setting its colour
# (c) getting the number of monitors and their sizes
#
#                                               JL 20140512, 20170220

import gi
gi.require_version('Gtk','3.0')
from gi.repository import Gtk, Gdk
import Xlib
from Xlib.display import Display
from Xlib import X

# Colour style for (b)
stylesheet=b"""
window#bar {
  background-color: darkred;
}
"""

#  the size of the bar (its height), in pixels
bar_size = 10

def main ():

    # Version information
    print("Gtk %d.%d.%d" % (Gtk.get_major_version(),
                            Gtk.get_minor_version(),
                            Gtk.get_micro_version()))

    # (a) Create an undecorated dock
    window = Gtk.Window()
    window.set_name("bar")
    window.set_type_hint(Gdk.WindowTypeHint.DOCK)
    window.set_decorated(False)
    window.connect("delete-event", Gtk.main_quit)

    # (b) Style it
    style_provider = Gtk.CssProvider()
    style_provider.load_from_data(stylesheet)
    Gtk.StyleContext.add_provider_for_screen(
      Gdk.Screen.get_default(),
      style_provider,
      Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION)

    # the screen contains all monitors
    screen = window.get_screen()
    width = screen.width() #width = Gdk.Screen.width()
    print("width: %d" % width)

    # (c) collect data about each monitor
    monitors = []
    nmons = screen.get_display().get_n_monitors()
    print("there are %d monitors" % nmons)
    for m in range(nmons):
      mg = screen.get_monitor_geometry(m)
      print("monitor %d: %d x %d" % (m,mg.width,mg.height))
      monitors.append(mg)

    # current monitor
    curmon = screen.get_monitor_at_window(screen.get_active_window())
    x = monitors[curmon].x
    y = monitors[curmon].y
    width = monitors[curmon].width
    height = monitors[curmon].height
    print("monitor %d: %d x %d (current, offset %d)" % (curmon,width,height,x))
    print("bar: start=%d end=%d" % (x,x+width-1))

    # display bar along the top of the current monitor
    window.move(x,y)
    window.resize(width,bar_size)

    # it must be shown before changing properties 
    window.show_all()

    # (d) reserve space (a "strut") for the bar so it does not become obscured
    #     when other windows are maximized, etc
    # http://stackoverflow.com/questions/33719686  property_change not in gtk3.0
    # https://sourceforge.net/p/python-xlib/mailman/message/27574603
    display = Display()
    topw = display.create_resource_object('window',
                                          window.get_toplevel().get_window().get_xid())

    # http://python-xlib.sourceforge.net/doc/html/python-xlib_21.html#SEC20
    topw.change_property(display.intern_atom('_NET_WM_STRUT'),
                           display.intern_atom('CARDINAL'), 32,
                           [0, 0, bar_size, 0 ],
                           X.PropModeReplace)
    topw.change_property(display.intern_atom('_NET_WM_STRUT_PARTIAL'),
                           display.intern_atom('CARDINAL'), 32,
                           [0, 0, bar_size, 0, 0, 0, 0, 0, x, x+width-1, 0, 0],
                           X.PropModeReplace)


    # we set _NET_WM_STRUT, the older mechanism as well as _NET_WM_STRUT_PARTIAL
    # but window managers ignore the former if they support the latter.
    #
    # the numbers in the array are as follows:
    #
    # 0, 0, bar_size, 0 are the number of pixels to reserve along each edge of the
    # screen given in the order left, right, top, bottom. Here the size of the bar
    # is reserved at the top of the screen and the other edges are left alone.
    #
    # _NET_WM_STRUT_PARTIAL also supplies a further four pairs, each being a
    # start and end position for the strut (they don't need to occupy the entire
    # edge).
    #
    # In the example, we set the top start to the current monitor's x co-ordinate
    # and the top-end to the same value plus that monitor's width, deducting one.
    # because the co-ordinate system starts at zero rather than 1. The net result
    # is that space is reserved only on the current monitor.
    #
    # co-ordinates are specified relative to the screen (i.e. all monitors together).
    #


    # main event loop
    # Gtk.main()
    # Control-C termination broken in GTK3 http://stackoverflow.com/a/33834721
    # https://bugzilla.gnome.org/show_bug.cgi?id=622084
    from gi.repository import GLib
    GLib.MainLoop().run()

if __name__ == "__main__":
    main ()

How would I calculate out the partial strut out of an array of booleans that enable anchors, integer margins values, position of the window, and size of the window? I'm doing this all in C.

Thanks! You're an absolute legend!