Re: Find out if a widget or window is actually visible?

[Toralf Lund <toralf procaptura com>]

> > > > Does Gtkmm/Gdkmm offer a nice and simple way to find out if a  
> > > > widget or
> > > > window is actually visible to the user, i.e. is mapped *and not  
> > > > obscured
> > > > by another window*? I mean, .e.g Gdk::Window::is_viewable () and
> > > > Gdk::Window::is_visible ()/Gtk::Widget::is_visible() will answer  
> > > > only
> > > > first half of that question, I believe, i.e. they will tell me  
> > > > whether
> > > > the window/widget is mapped, but not check if it is covered by  
> > > > something
> > > > else.
> > > >
> > > > - Toralf
> > > >
> > > >         
> > > I am not sure if it about GTKmm at all. The system manages windows
> > > that represent a space for different applications. Each application
> > > can be written using it's own GUI framework: GTKmm, Qt, Tkinter, and
> > > so on. Thus maybe your question should be addressed to a "guy"  
> > > that is
> > > responsible for sending a sort of "REDRAW_WINDOW" signal whenever it
> > > is needed and a part of window becomes visible. I guess that  
> > > should be
> > > some kind of System GUI Manager that is definitely different in  
> > > Linux,
> > > Windows, Mac OS X, etc. Therefor the "guy" you are looking is System.
> > >       
> > No, I don't think so. By that argument, Gdk::Window should never be
> > used. Or even be there in the first place. No, wait, you can make that
> > all of Gdk. And add the event handling infrastructure in Gtk.  
> > 'Cause the
> > job is done by the back-end GUI libs or windowing system, really...
> > But isn't one of the prime features of Gtk actually that it allows you
> > to interact with windows without having to worry about system  
> > details or
> > platform differences? It's a cross-platform toolkit, you see...
> >     
>
> However, this question is "different".  For one, the system may  
> provide no means of finding out.  And in some systems, "visible" may  
> not be meaningful.  There's an X server I've seen that renders  
> everything, unobscured, offscreen, and then does some quite advanced  
> and strange compositing.  The question of "visibility" is next-to- 
> meaningless in the context of that system.
True. Actually, in X, anything that involves interaction with the window 
manager is inaccurate as ultimately, the window manager may do as it 
pleases.

However, I don't agree that just because something can't be implemented 
on *some* system, it should be left out on *all* platforms. Actually, 
I'm sure that there is already functionality in Gtk/Gdk that won't work 
if, say, you use a weird X server or WM. But should that keep us from 
using it? I don't think so. We should just handle failure or missing 
information in a controlled manner. And I believe visibility is 
meaningful on *most* systems...

- Toralf