Re: drawables and refresh rates

[Rob Benton <rob benton conwaycorp net>]

Carl Nygard wrote:
> On Fri, 2004-12-03 at 04:43, Andrew E. Makeev wrote:
>
> > Rob Benton wrote:
> >
> >
> > > Andrew E. Makeev wrote:
> > >
> > >
> > > > Before to answer you, we need to know how do you "draw" your circles? 
> > > > The common way is to use expose_event to redraw only those parts of 
> > > > the drawing area that actually were changed. In this case I never 
> > > > seen any flickering in my applications even on Celeron 300Mhz.
> > >
> > > Right now I'm using 2 methods.  Method A handles the expose event of 
> > > the Gtk::DrawingArea which then calls method B.  Method B is also 
> > > connected to the value changed signal of both the Gtk::HScale widgets.
>
>
> I do something like:
>
> Method A handles expose events, and redraws exposed rectangle from
> internal pixmap.
>
> Method B connected to value changed signal, draws to internal pixmap,
> calls queue_draw() which eventually triggers Method A.

Carl I did some reading on double buffering.  Where I've been stuck is
that in order to start drawing to a Gdk::Drawable, it has to be realized
first.  Pixmap looks like what I need but its create methods all take a 
Glib::RefPtr<Gdk::Drawable>.  And I get a segfault when I try that.

> You can add efficiency by keeping track of the bounding box of what you
> redraw, and only trigger expose events for those rectangles.

How would I do that?  I have 1 drawing area widget which
is 100x100.  I draw a complete blue circle and then a red arc on top of
that.  Finally, to smooth out the edges I load an svg which is a smooth
black circle outline.  The flickering comes even if I don't use
window->clear() just b/c each draw command overlaps the previous one.

Thanks for all the help.