How to create PyGTK Gnome Screensaver?

skykooler · 12-15-2010, 09:51 PM

I have created a PyGTK app (a binary clock) that I would like to turn into a screensaver. I added the .desktop file to /usr/share/applications/screensavers/ but all I get when I select it is a black screen. On the GnomeScreensaver FAQ (here) it says to use a gsthemewindow as the toplevel window, but the libraries given are in C. Is there any way to:

Import this C library to get access to this toplevel window,
Convert this GTK+ C library to PyGTK,
or use a pygtk app as a screensaver in some other way?

Moved: This thread is more suitable in Programming and has been moved accordingly to help your thread/question get the exposure it deserves.

Julian Andrews · 01-23-2011, 02:34 PM

I had a similar question myself, and was unable to find any good documentation online. I did, however find code which accomplishes exactly what you are looking for. (I found it in a project called gphotoframe - since this is my first post, I can't post any actual links). To save you some time, here's a somewhat stripped down version of the code you probably need:

Code:

class GsThemeWindow(gtk.Window):
    __gtype_name__ = 'GsThemeWindow'
    
    def __init__(self):
        super(GsThemeWindow, self).__init__()

    def do_realize(self):
        ident = os.environ.get('XSCREENSAVER_WINDOW')
        if ident:
            self.window = gdk.window_foreign_new(int(ident, 16))
            self.window.set_events(gdk.EXPOSURE_MASK | gdk.STRUCTURE_MASK)
            x, y, w, h, depth = self.window.get_geometry()
            self.size_allocate(gdk.Rectangle(x, y, w, h))
            self.set_default_size(w, h)
            self.set_decorated(False)
        else:
            self.window = gdk.Window(
                self.get_parent_window(),
                width=self.allocation.width,
                height=self.allocation.height,
                window_type=gdk.WINDOW_TOPLEVEL,
                wclass=gdk.INPUT_OUTPUT,
                event_mask=self.get_events() | gdk.EXPOSURE_MASK)
        self.window.set_user_data(self)
        self.set_flags(self.flags() | gtk.REALIZED)
        self.style.attach(self.window)

You will, of course, also need to write a .desktop file, but most of your other problems should be solved by using one of these GsThemeWindow objects in place of your application's main gtk.Window. As far as I can tell, this code simply tries to find as XSCREENSAVER_WINDOW to draw to, and if that fails, it creates a standalone window.

skykooler · 01-24-2011, 01:56 AM

Thank you, but how do I use the new window type? Here is the code I am using for my app ( a binary clock app) - for some reason Cairo won't draw anything to the screen. The button (only there for testing purposes) shows up fine in regular mode, but not when run as a screensaver.

Code:

#!/usr/bin/python
import sys
import os
import gtk
from gtk import gdk
import cairo
import time
import gobject
launchpad_available = False

# Add project root directory (enable symlink, and trunk execution).
PROJECT_ROOT_DIRECTORY = os.path.abspath(
    os.path.dirname(os.path.dirname(os.path.realpath(sys.argv[0]))))

if (os.path.exists(os.path.join(PROJECT_ROOT_DIRECTORY, 'gbinclock'))
    and PROJECT_ROOT_DIRECTORY not in sys.path):
    sys.path.insert(0, PROJECT_ROOT_DIRECTORY)
    os.putenv('PYTHONPATH', PROJECT_ROOT_DIRECTORY) # for subprocesses

def d2b(n):
	x=bin(n)[2:]
	y=[0, 0, 0, 0, 0, 0]
	for i in range(0, len(x)):
		y[i-len(x)]=x[i]
	return y

class GsThemeWindow(gtk.Window):
    __gtype_name__ = 'GsThemeWindow'
    def __init__(self):
        super(GsThemeWindow, self).__init__()
    def do_realize(self):
        ident = os.environ.get('XSCREENSAVER_WINDOW')
        if ident:
            self.window = gdk.window_foreign_new(int(ident, 16))
            self.window.set_events(gdk.EXPOSURE_MASK | gdk.STRUCTURE_MASK)
            x, y, w, h, depth = self.window.get_geometry()
            self.size_allocate(gdk.Rectangle(x, y, w, h))
            self.set_default_size(w, h)
            self.set_decorated(False)
        else:
            self.window = gdk.Window(
                self.get_parent_window(),
                width=self.allocation.width,
                height=self.allocation.height,
                window_type=gdk.WINDOW_TOPLEVEL,
                wclass=gdk.INPUT_OUTPUT,
                event_mask=self.get_events() | gdk.EXPOSURE_MASK)
        self.window.set_user_data(self)
        self.set_flags(self.flags() | gtk.REALIZED)
        self.style.attach(self.window)
        vbox = gtk.VBox(False, 0)
        self.add(vbox)
        drawingarea1 = gtk.DrawingArea()
	drawingarea1.set_size_request(500, 500)
        vbox.show()
        vbox.pack_start(drawingarea1, True, True, 0)
        drawingarea1.show()
        abutton = gtk.Button("OK")
        abutton.set_use_stock(True)
        abutton.set_size_request(50, -1)
        vbox.pack_start(abutton, True, True, 0)
        abutton.show()
        self.show()
        cra = drawingarea1.window.cairo_create()
        x,y,w,h = drawingarea1.allocation
        self.expose_event(cra, x, y, w, h)
        self.connect("expose-event", self.expose_event)
        self.connect("destroy", self.on_destroy)
    def expose_event(self, cra, x, y, w, h):
        print "g"
        timemat = [d2b(time.localtime(time.time())[3]), d2b(time.localtime(time.time())[4]), d2b(time.localtime(time.time())[5])]
        surf = cairo.ImageSurface(cairo.FORMAT_ARGB32, w,h)
        cr = cairo.Context(surf)
        surface = cairo.ImageSurface.create_from_png("/usr/share/gbinclock/media/background.png")
        pattern = cairo.SurfacePattern(surface)
        pattern.set_extend(cairo.EXTEND_REPEAT)
        cr.set_source(pattern)
        cr.paint()
        try:
            print sys.argv[1]
            if sys.argv[1]=="1":
                for i in range(0, 3):
                    py = 0-(h/3.0*(i+0.5))
                    for j in range(0, 6):
                        px = (w/6.0*(5-j+0.5))-w+32
                        if timemat[i][j]=="1":
                            surface = cairo.ImageSurface.create_from_png("/usr/share/gbinclock/media/light_on.png")
                        else:
                            surface = cairo.ImageSurface.create_from_png("/usr/share/gbinclock/media/light_off.png")
                        pattern = cairo.SurfacePattern(surface)
                        pattern.set_extend(cairo.EXTEND_NONE)
                        matrix = cairo.Matrix(1,0,0,1,px,py)
                        pattern.set_matrix(matrix)
                        cr.set_source(pattern)
                        cr.paint() 
            else:
                for i in range(0, 3):
                    px = 0-(w/3.0*(i+0.5))
                    for j in range(0, 6):
                        py = (h/6.0*(5-j+0.5))-h+32
                        if timemat[i][j]=="1":
                            surface = cairo.ImageSurface.create_from_png("/usr/share/gbinclock/media/light_on.png")
                        else:
                            surface = cairo.ImageSurface.create_from_png("/usr/share/gbinclock/media/light_off.png")
                        pattern = cairo.SurfacePattern(surface)
                        pattern.set_extend(cairo.EXTEND_NONE)
                        matrix = cairo.Matrix(1,0,0,1,px,py)
                        pattern.set_matrix(matrix)
                        cr.set_source(pattern)
                        cr.paint()
        except:
                for i in range(0, 3):
                    px = 0-(w/3.0*(i+0.5))
                    for j in range(0, 6):
                        py = (h/6.0*(5-j+0.5))-h+32
                        if timemat[i][j]=="1":
                            surface = cairo.ImageSurface.create_from_png("/usr/share/gbinclock/media/light_on.png")
                        else:
                            surface = cairo.ImageSurface.create_from_png("/usr/share/gbinclock/media/light_off.png")
                        pattern = cairo.SurfacePattern(surface)
                        pattern.set_extend(cairo.EXTEND_NONE)
                        matrix = cairo.Matrix(1,0,0,1,px,py)
                        pattern.set_matrix(matrix)
                        cr.set_source(pattern)
                        cr.paint()
        cra.set_source_surface(surf)
        cra.paint()
        source_id = gobject.timeout_add(100, self.expose_event, cra, x, y, w, h)
    def quit(self, widget, data=None):
        """Signal handler for closing the GsThemeWindow."""
        self.destroy()
    def on_destroy(self, widget, data=None):
        """Called when the GbinclockWindow is closed."""
        # Clean up code for saving application state should be added here.
        gtk.main_quit()

if __name__ == "__main__":
    # Run the application.
    window = GsThemeWindow()
    window.show()
    window.set_decorated (False);
    window.set_skip_taskbar_hint (True);
    window.set_skip_pager_hint (True);
    window.set_keep_above (True);
    window.fullscreen();
    gtk.main()

Julian Andrews · 01-24-2011, 12:14 PM

Hi,

First, a caveat - I'm pretty far from an expert in GTK, in fact, this screensaver was my first GTK project. That said, I was also using a gtk.DrawingArea with cairo in a box, so what worked for me ought to work for you!

I think the problem with your code has to do with how you're dealing with expose events. When I run your code, I get a TypeError every time an actual expose_event signal comes down the line (rather than your direct calls of expose_event) because the wrong number of arguments are being passed. If gnome-screensaver gets an error when it tries to run the code, it will stop running the screensaver even if the main thread doesn't crash. You might want to create a custom drawing area class to do your drawing.

Code:

class MyDrawingArea(gtk.DrawingArea):
    __gsignals__ = {"expose_event": "override"}
    
    def do_expose_event(self, event):
        cra = self.window.cairo_create()
        x = event.area.x
        y = event.area.y
        w = event.area.width
        h = event.area.height
        # Your drawing code here

    def run(self):
        self.queue_draw()
        gobject.timeout_add(100, self.run)

Then don't connect expose events in the main window, and instantiate a custom drawing area object instead of the generic gtk.DrawingArea. When I ran your code modified like this, I was able to get it to draw some shapes (obviously without your graphics, I couldn't easily test your whole drawing routine.) Also, you don't really want to queue a new expose event on every expose event since this will lead to an ever increasing number of timeouts, and program slowdown. I've suggested one possible approach above - you can call run on your drawing area once you've instantiated it.

I hope this helps!