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 Post subject: GTK Fade with state change
PostPosted: Thu Aug 30, 2012 8:05 pm 

Joined: Fri Jul 13, 2012 3:25 pm
Posts: 2
Using GTK 3.4.2 on ubuntu with python.

Hi Guys,

I've looked everywhere for this:

I have a horizontal box with 2 buttons, 2 labels and a seperator that I want to fade out to transparent. At first I thought I could just remove a class from a StyleContext and add another to achieve the effect (like you would do with javascript / CSS). Something like


But that didn't work out, because the box was not redrawn.

My next approach was (or better is) to set the box to insensitive. I can then style the box with #status_bar_box:insensitive { ... } (CSS) but there is no transition (note that I added the transition to both, normal and :insensitive).

self.status_bar.set_state_flags(Gtk.StateFlags.INSENSITIVE, True)

Has anyone solved this? Or is there a simple ""cairo"" approach that I could choose? (I would prefer CSS, it's so clean ... )

Many Thanks,


 Post subject: Re: GTK Fade with state change
PostPosted: Sat Sep 01, 2012 5:38 am 
GTK+ Guru

Joined: Fri Mar 25, 2011 5:16 pm
Posts: 180
Location: USA
I don't know Python at all only C but I'll try to help.

When you say "fade out to transparent" and "transition" I assume your talking about when your cursor hovers over any part of the horizontal box.
You can't apply CSS to a container widget. They don't have any gtk_widget_class_install_style_property() in their main files. (compare gtkgrid.c to gtkbutton.c)

There's an example for a transparent window in the GTK+ tests folder (testgtk.c) called alpha window.

I'm not sure how you would get an animated fade but you could use a drawing area in place of the horizontal box. Then detect when the mouse enters using gtk_widget_add_events() and modify the drawing area and widgets inside to be transparent.

Other than that you might have to wait for gtk+3.6 to be release in October with Ubuntu Quantal . It's supposed to have better support for transitions and CSS animations. Again that's GTK+ I'm not sure about Python.
(Link below says 3.4 but also talks about 3.6 and has a video)

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