'synchronous redraw' with a DrawingArea

[Pascal Ognibene <pascal ognibene libertysurf fr>]

Hi all,

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)

Sorry for the verbose mail. Not easy to describe :-)

Thank's for your help.

Pascal