Re: Whats the right way to add gtk components to Emacs?

[Jan Djärv]

address@hidden skrev 2011-07-02 17.53:
> I the Xwidget branch I add gtk components to the buffer. It works mostly
> well. Some cases dont work too well:
>
> - If I create a new toplevel window and add a component to it, Emacs
>    crashes.

Interesting.  I guess the assumtion is that Gtk top level windows are frames.
Tooltips are a special case.

> - If I make an offscreen buffer and try to catch damage events, many
>    events seemingly get lost.
>
> Emacs does some kind of trickery with X events which I suspect is the
> root cause. How does this work? How do I make my more complicated
> components work in this scheme?

Hard to tell, since "this scheme" is not very detailed.  But here is the big 
picture.

In x_term_init, we first make sure no extended input events are used:

        /* Emacs can only handle core input events, so make sure
           Gtk doesn't use Xinput or Xinput2 extensions.  */
        {
          static char fix_events[] = "GDK_CORE_DEVICE_EVENTS=1";
          putenv (fix_events);
        }

Then we install an event filter:
        /* NULL window -> events for all windows go to our function */
        gdk_window_add_filter (NULL, event_handler_gdk, NULL);

All events go to that function.  It in turn calls handle_one_xevent which is 
the big event switch.  handle_one_xevent may deside that it is inappropriate 
to forward some events to Gtk+, so it sets flags that event_handler_gdk 
inspects.  Some events go to Gtk+, some are dropped.  The reason for dropping 
events is that they conflict with what Emacs does (i.e. clears/redraws 
windows, takes actions on property notify, and more).

All this complication is because it was desided that the big event switch 
should be used for Gtk+ also, i.e. keep code duplication to a minimum.

        Jan D.