Re: 'synchronous redraw' with a DrawingArea

[Pascal Ognibene <pascal ognibene libertysurf fr>]

Sven Neumann wrote:

> Hi,
>
> Pascal Ognibene <pascal ognibene libertysurf fr> writes:
>
>  
>
> > I've an application with one main window where I draw some
> > diagrams, and a collection of dialog boxes, always transient for
> > the main window (that is, they're always on the top).
> >
> > When I do modifications in a dialog box and close it it should refresh
> > the diagram immediately then close the box.
> >
> > But it looks like the redraw of the drawing area is only made
> > in parts not previously covered by the dialog box. As a result,
> > some parts of the diagram are correct, while other
> > are not redrawn until I scroll the window for example.
> >
> > Is there any way to force the redraw 'synchronously' to be sure
> > that the view is correct when the transient dialog box is closed?
> > (note that I use the default double buffering of gtk2 for the
> > drawing area)
> >    
>
> X11 does enforce some restrictions on what you can do. The content of
> a window obscured by another other windows needs be redrawn when it
> becomes visible. There's basically no way around this. For this reason
> your application window has to be able to redraw itself whenever a
> part of it is exposed. You also must only draw in the expose_event
> handler. If you follow that simple rule, things will just work.
>
>
> Sven
>
>  
Well, I do redraw in the expose_event handler... But I've realized that
my description of the problem was not accurate :-(

-I do stuff in my dialog box
-I close my dialog
-the expose_event of the drawing area is called. Only parts
that were *hidden* by the dialog box are redrawn. So 'old' parts
remain the same.

I could of course post another expose event to the drawing area but:

1) I'm not sure it would work if X11 or GTK try to merge the expose events
for optimization. This mostly depends on the timing I guess
2) if it works there would be one useless redraw...

Again, any help is welcome :-)

Pascal