Web Buzz Forum - Writing a simple desktop widget for Ubuntu

I needed a way to display the contents of an HTML file on my desktop, in such a way that it looks like it’s part of the wallpaper. Fortunately, most of the answer was in How can I make my own custom desktop widgets? on Ask Ubuntu, along with Create a Gtk Window insensitive to Show Desktop and Won’t show in Launcher. Combining that with the excellent Python GI API Reference which contains everything and which I can never find when I go looking for it, I came up with a simple little Python app. I have it monitoring the HTML file which it displays for changes; when that file changes, I refresh the widget.

from gi.repository import WebKit, Gtk, Gdk, Gio
import signal, os

class MainWin(Gtk.Window):
    def __init__(self):
        Gtk.Window.__init__(self, skip_pager_hint=True, skip_taskbar_hint=True)
        self.set_wmclass("sildesktopwidget","sildesktopwidget")
        self.set_type_hint(Gdk.WindowTypeHint.DOCK)
        self.set_size_request(600,400)
        self.set_keep_below(True)

        # transparency
        screen = self.get_screen()
        rgba = screen.get_rgba_visual()
        self.set_visual(rgba)
        self.override_background_color(Gtk.StateFlags.NORMAL, Gdk.RGBA(0,0,0,0))

        self.view = WebKit.WebView()
        self.view.set_transparent(True)
        self.view.override_background_color(Gtk.StateFlags.NORMAL, Gdk.RGBA(0,0,0,0))
        self.view.props.settings.props.enable_default_context_menu = False
        self.view.load_uri("file://path/to/html/file")

        box = Gtk.Box()
        self.add(box)
        box.pack_start(self.view, True, True, 0)
        self.set_decorated(False)
        self.connect("destroy", lambda q: Gtk.main_quit())

        self.show_all()
        self.move(100,100)

def file_changed(monitor, file, unknown, event):
    mainwin.view.reload()

if __name__ == '__main__':
    # the HTML file needs to have background colour rgba(0,0,0,0)
    gio_file = Gio.File.new_for_path("/path/to/html/file")
    monitor = gio_file.monitor_file(Gio.FileMonitorFlags.NONE, None)
    monitor.connect("changed", file_changed)
    mainwin = MainWin()
    signal.signal(signal.SIGINT, signal.SIG_DFL) # make ^c work
    Gtk.main()

Lots of little tricks in there: the widget acts as a widget (that is: it stays glued to the desktop, and doesn’t vanish when you Show Desktop) because of the Gdk.WindowTypeHint.DOCK, skip_pager_hint=True, skip_taskbar_hint=True, and set_keep_below(True) parts; it’s transparent because the HTML file sets its background colour to rgba(0,0,0,0) with CSS and then we use override_background_color to make that actually be transparent; the window has no decorations because of set_decorated(False). Then I just add it to Startup Applications and we’re done.


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