On Fri, 2005-03-04 at 23:02 +0100, Andreas Klostermann wrote:
> I try to fix a bug in the gtk frontend. When moving the cursor "out of
> sight", normally the view should follow it by centering. Now, with the
> gtk frontend, it will scroll crazily around, making the application
> unrespondible.
> I'm trying to fix it, but I don't quite understand the flow of signals.
> Could someone give me details on how this works?
A while back, Alfredo Braunstein wrote:
> I know what this it: the gtk frontend fires the "scrolling" signal
> when
> setting the scrollbar parameters from inside LyX: the kernel expects
> that
> setting the parameters only changes the scrollbar visually (and
> invokes no
> scrolling). This results in an infinite loop.
> There was a similar problem in the qt frontend, that was solved by
> deactivating the signal somewhere IIRC. Unfortunately I cannot look at
> the
> problem more closely ATM.
To illustrate the situation more clearly for you, in GWorkArea.C:
line 196:
vscrollbar_.get_adjustment()->signal_value_changed().connect(
sigc::mem_fun(*this, &GWorkArea::onScroll));
So onScroll gets called whenever the adjustment object associated with
the vertical scrollbar is changed. Fine. That's there to catch user
input. However, at line 356 in setScrollbarParams (which the backend
calls):
adjustment->set_value(pos);
That in turn triggers onScroll, which tells LyX to scroll, which tells
the frontend to update its scrollbar, ad infinitum.
John
