Re: Strange behavior

["Matt Hoosier" <matt hoosier gmail com>]

On 6/11/07, Robert Caryl <bob fis-cal com> wrote:
> We have encountered a strange problem:
>
> We derive a window from Gtk::Window.  We add three Gtk::HBox containers
> to the window.  In the first we pack three Gtk::Label objects, each of
> which display some status text.  In the second we have a dynamically
> created menu.  In the third we have a Gtk::DrawingArea.  We have
> overridden the Gtk::Window::on_expose_event to rescale a Gtk::Image and
> render that image into the Gtk::DrawingArea.

That's an interesting choice on how to get the image rendered into the
drawing area. Is there a particular reason that you didn't choose to
override the expose-event virtual method of Gtk::DrawingArea instead?

> Here is the strange behavior:  When we allow the Gtk::Image to be
> rendered into the Gtk::DrawingArea, the Gtk::Label objects in the first
> Gtk::HBox are not displayed (or perhaps they are obscured).  If I
> comment out the code in the Gtk::Window::on_expose_event, the Gtk::Label
> objects in the first Gtk::HBox are displayed.  The menu in the second
> Gtk::HBox is unaffected in both cases.

Just a stab: if your expose handler for the toplevel Window looked like:

 bool
 on_expose_event(GdkEventExpose* e)
 {
   Gtk::Window::on_expose_event(e);

   draw_image_onto_drawing_area();
   return true;
 }

then any work you do after the chain up to the base class code, is
going to stomp on the children widgets' painting. As for why the menu
still appears, perhaps it uses a dedicated GdkWindow (I don't have the
code handy to look at right now). Widgets that do their rendering to
an independent native window will still survive an unorthodox ordering
like the code above.

> I know someone is going to ask for the code, but until my co-worker
> arrives I cannot comply.  Any ideas?
>
> --
>
> *Robert L. Caryl Jr.*
> Fiscal Systems, Inc.
> 102 Commerce Circle
> Madison, AL 35758-2706 USA
> 256-772-8922 ext. 108
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