Re: Include GdkRegion in expose events - bug 51288 [PATCH]

[Alexander Larsson <alla lysator liu se>]

On 28 Feb 2001, Owen Taylor wrote:

> I think if we are going to break synthetic exposes, then we
> should break them in a clear, reliable way and tell people
> need to
>
> So, I'd propose make calling gtk_widget_event() with an
> event of type GDK_EXPOSE illegal and if that is done
> print out a informative message like:
>
>  "Events of type GDK_EXPOSE cannot be synthesized. To get
>   the same effect, call gdk_window_invalidate_rect/region(),
>   followed by gdk_window_process_updates()."
>
> With that change (and fixing gtknotebook.c to simple invalidate_rect
> and not process_updates()), it should be fine to commit.

This wasn't as easy as it looked.

The problem is that all container expose handlers must generate synthetic
expose events for all NO_WINDOW children. This means gtk_widget_event()
is called with GDK_EXPOSE events.

This also means that code in all gtk+ container widgets like this:
 if (GTK_WIDGET_DRAWABLE (child->widget) &&
     GTK_WIDGET_NO_WINDOW (child->widget) &&
     gtk_widget_intersect (child->widget, &event->area, &child_event.area))
 	gtk_widget_event (child->widget, (GdkEvent*) &child_event);

must be changed to something like this:
 if (GTK_WIDGET_DRAWABLE (child->widget) &&
     GTK_WIDGET_NO_WINDOW (child->widget) &&
     gtk_widget_region_intersect (child->widget, event->region,
                                  &child_event.region, &child_event.area))
        {
 	  gtk_widget_event (child->widget, (GdkEvent*) &child_event);
          gdk_region_destroy (child_event.region);
        }

This is a source incompatible change that needs changes in all container
widgets. If you forget to change this in a widget, things will "kinda"
work anyway. This can be both good (don't break source compat badly) and
bad (hard to detect bugs).

If we want a clean break here we will probably need a *public*
gtk_widget_expose_event () call, documenting when this function is
supposed to be used. Then we make expose events in gtk_widget_event()
invalid (g_warning + return). Do you want me do this?

/ Alex