#56917 Add corner widget to GtkScrolledWindow

[Owen Taylor <otaylor redhat com>]

> > 56917 Add corner widget to GtkScrolledWindow
> >   Notes:    May be various issues with key navigation, theming
> >             etc. Seems late to put in this kind of UI addition.
> >   Puntable: Yes
> >   Breakage: Possible binary incompat
> >   Time:     ? 
> 
> i sent an email out on this and saw no replies about key navigation
> or themeing issues

Well, no reply != no problems. I suspect that a cross-toolkit assistive
technology product may have trouble when a scrolled-window has two
children other than the scrollbars... but leaving that aside, I guess
my bopinion is that this is not a good user interface feature,.

> which as i mentioned in my email btw, will not
> impose any problems. so is there actually anything pending that prevents
> me from comitting the code?

Well, basically, the issue is that sticking a widget someplace because
it fits there is generally not a great idea. Since the space is an
theme-dependent square of at most, about 20x20 pixels, if we make
this easy to do, then we'll see tons of apps with little unidentifiable
buttons there that all do different things. (Which have to be accessible
through the interface in some other way, because most people will
never try clicking on the little mysterious button at all.)

If there was a _standard_ thing for a button there to do, then people
might learn what it did, but I don't think there is a sensible
standard thing todo for such a button to do.

Also note that if you _really_ want to do this, an ALWAYS/ALWAYS scrolled
window is easy enough to simulate with a table, unlike one with
an AUTOMATIC policy.

Finally, I can think of almost no cases where ALWAYS/ALWAYS scrollbars
are a good choice.

Anyways, it wouldn't be the worst piece of "API bloat to enable something
people shouldn't do anyways" in GTK+, and I'm not going to put up a 
big fight over it. But I don't think it actually makes GTK+ a better
toolkit for creating useable applications.

There is a reason why this feature isn't in common use. (Quick search 
reveals that  the feature exists in Qt, but not in WinForms or Swing.)

Regards,
                                                  Owen