Preventing window overlap in GTK

Question

I've got a Python/Linux application that displays bits of info I need in a GTK window. For the purposes of this discussion, it should behave exactly like a dock - exists on all virtual desktops, and maximized windows do not overlap it.

The first point is pretty easy, but I have spent days bashing my head against my monitor trying to get the second point - preventing overlap. My app should not be covered if another window is maximized. Setting "always on top" is not enough, as the other windows just sit behind my info bar instead of stopping at its edge.

In short: with a dock/panel style window, how can you prevent other windows from maximizing over/under it?

Update: Problem solved thanks to vsemenov

Ajay

Answer 1

Use _NET_WM_STRUT and _NET_WM_STRUT_PARTIAL (for backwards compatibility) properties to reserve space at the edge of X Window System desktop.

With PyGtk you can set these properties like so, assuming self.window is an instance of gtk.Window:

self.window.get_toplevel().show() # must call show() before property_change()
self.window.get_toplevel().window.property_change("_NET_WM_STRUT", 
    "CARDINAL", 32, gtk.gdk.PROP_MODE_REPLACE, [0, 0, 0, bottom_width]) 

Clarification on the data parameter [0, 0, 0, bottom_width] in above:

This parameter specifies the width of reserved space at each border of the desktop screen in order: [left, right, top, bottom]. So [0, 0, 0, 50] would reserve 50 pixels at the bottom of the desktop screen for your widget.

Here is a simple working example:

import gtk

class PyGtkWidgetDockExample:
    def __init__(self):
        self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)
        self.window.set_default_size(100, gtk.gdk.screen_height())
        self.window.move(gtk.gdk.screen_width()-100, 0)
        self.window.set_type_hint(gtk.gdk.WINDOW_TYPE_HINT_DOCK)        
        self.window.show()          
        self.window.window.property_change("_NET_WM_STRUT", "CARDINAL", 32, 
            gtk.gdk.PROP_MODE_REPLACE, [0, 100, 0, 0])               

app = PyGtkWidgetDockExample()
gtk.main()

Colchester

That's a huge help, and clarifies some of the code I found in PyPanel when attempting to solve this. I see the docs show this as property_change(property, type, format, mode, data) can you clarify the data being sent? I get the height, can you tell me about the zeros? – Ajay

Hmm thanks for reply. I'm using screen = gtk.gdk.screen_get_default() root = screen.get_root_window() root.property_change("_NET_WM_STRUT", "CARDINAL", 32, gtk.gdk.PROP_MODE_REPLACE, [0, 0, 0, 64]) with no luck. It's the root window you're referring to right? Or my application's window? I'm not having luck either way. – Ajay

Same when changing properties application's window. No errors but no apparent effect – Ajay

@Josh: you want to call property_change on the top level window of your app, which you can reference from any gtk.Window using self.window.get_toplevel().window.property_change(). If you go the route of gtk.gdk.screen_get_default().get_root_window(), it will return all gtk apps, through which you will have to loop to find your own, i.e.: for i in gtk.gdk.screen_get_default().get_root_window().get_children(). I updated my post with a working example, hopefully you can get this feature working in your application. – Colchester

Is it possible you're testing with a window manager that doesn't support these properties? – Mme

Fantastic! Got it! Thanks all, especially, vsemenov! – Ajay

For any future readers of this question, it appears that the properties must be set AFTER the show() method is called. I was stuck on that for about an hour. – Ajay

Updated answer highlighting having to call show() before property_change(). – Colchester

@vls: do you have any idea as to how to do the same with Qt4? See thread. Thanks. – Inviolate

In Gtk+3 Gtk.Window.window (or Gtk.Window.get_top_level().window) does not have the property_change() method. I haven't been able to port it. Do you have any clue? The above answer will otherwise deprecate as Gtk+3 will replace Gtk+2. Thanks. – Inviolate

Hi again: i've been so far as Gdk.property_change(self.window.get_toplevel().window, "_NET_WM_STRUT", "CARDINAL", 32, Gdk.PropMode.REPLACE, [0,0,24,0], 4) using PyGI with Gtk+3, but that won't work because arg 1 and 2 should be of Gdk.Atom type and the Gdk.atom_intern() method isn't available (?), so I can't make the conversion. Also I am not sure about arg -1. See doc on Gdk Properties and Atoms. – Inviolate

Is this opposite of this possible? Im trying to make my fullscreen window overlap the dock but it wont consistently do it. – Magdamagdaia