How to get a transparent background in a window with PyGTK and PyCairo?

Question

I tried very hard to create a window without decorations and a transparent background using PyGTK. Then I will draw the contents of the window with Cairo. But I can’t make it work.

I tried many different ways, they all failed, this is one of them

#!/usr/bin/env python import pygtk pygtk.require('2.0') import gtk, sys, cairo win = None def expose (widget, event): cr = widget.window.cairo_create() #Start drawing cr.set_operator(cairo.OPERATOR_CLEAR) cr.set_source_rgba(0.5,1.0,0.0,0.5) cr.rectangle(0, 0, 0.9, 0.8) cr.fill() def main (argc): global win win = gtk.Window() win.set_decorated(False) win.connect('delete_event', gtk.main_quit) win.connect('expose-event', expose) win.set_app_paintable(True) win.show() gtk.main() if __name__ == '__main__': sys.exit(main(sys.argv)) 

So what is the easiest way to do this?

Answer 1

So, I figured it out myself.

This is a working example. I commented on the relevant parts just in case anyone else is interested in how to do this.

 #!/usr/bin/env python import pygtk pygtk.require('2.0') import gtk, sys, cairo from math import pi def expose (widget, event): cr = widget.window.cairo_create() # Sets the operator to clear which deletes everything below where an object is drawn cr.set_operator(cairo.OPERATOR_CLEAR) # Makes the mask fill the entire window cr.rectangle(0.0, 0.0, *widget.get_size()) # Deletes everything in the window (since the compositing operator is clear and mask fills the entire window cr.fill() # Set the compositing operator back to the default cr.set_operator(cairo.OPERATOR_OVER) # Draw a fancy little circle for demonstration purpose cr.set_source_rgba(0.5,1.0,0.0,1) cr.arc(widget.get_size()[0]/2,widget.get_size()[1]/2, widget.get_size()[0]/2,0,pi*2) cr.fill() def main (argc): win = gtk.Window() win.set_decorated(False) # Makes the window paintable, so we can draw directly on it win.set_app_paintable(True) win.set_size_request(100, 100) # This sets the windows colormap, so it supports transparency. # This will only work if the wm support alpha channel screen = win.get_screen() rgba = screen.get_rgba_colormap() win.set_colormap(rgba) win.connect('expose-event', expose) win.show() 

Answer 2

The exact problem was resolved on the forum. But this is in C ++. Try to figure it out.

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See comment posted by phorgan1. Hope this helps ...