[PATCH] Allow null surface arguments in wl_pointer.leave and wl_keyboard.leave

[Kristian Høgsberg]

On Mon, Jul 08, 2013 at 12:10:54PM +0100, Rob Bradford wrote:
> *bump*
> 
> This is a fix for:
> https://bugs.freedesktop.org/show_bug.cgi?id=65726&list_id=320167
> 
> Although it might be much better if we could emit the event
> (especially the leave) before we destroy the surface - that being said
> the destruction of the object will also result in the proxy being
> removed from the map and so when the event is received the callback
> will still have a NULL pointer.

The problem with the patch is that if we follow this logic, the
otherwise useful allow-null attribute breaks.  All object references
can potentially be destroyed between the time the server sends the
event and the time the client receives the event.  So I'm more in
favor of changing the order of events so we send out the event before
destroying the wl_resource.

Kristian

> Rob
> 
> On 17 June 2013 23:56, Jason Ekstrand <jason at jlekstrand.net> wrote:
> > The current specified behavior does not allow a null surface in either of
> > these events.  However, if the client calls wl_surface.destroy while the
> > surface has focus then the leave handler will get a null surface anyway
> > because the proxy corresponding to the wl_surface no longer exists.  This
> > change makes this edge-case explicit and allows the server to avoid sending
> > an event with an argument it knows the client has destroyed.
> >
> > Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
> > ---
> >  protocol/wayland.xml | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/protocol/wayland.xml b/protocol/wayland.xml
> > index 3d4ec9b..faa284e 100644
> > --- a/protocol/wayland.xml
> > +++ b/protocol/wayland.xml
> > @@ -1313,13 +1313,14 @@
> >      <event name="leave">
> >        <description summary="leave event">
> >         Notification that this seat's pointer is no longer focused on
> > -       a certain surface.
> > +       a certain surface.  The surface parameter may be null if the
> > +       surface has been destroyed.
> >
> >         The leave notification is sent before the enter notification
> >         for the new focus.
> >        </description>
> >        <arg name="serial" type="uint"/>
> > -      <arg name="surface" type="object" interface="wl_surface"/>
> > +      <arg name="surface" type="object" interface="wl_surface" allow-null="true"/>
> >      </event>
> >
> >      <event name="motion">
> > @@ -1430,13 +1431,14 @@
> >      <event name="leave">
> >        <description summary="leave event">
> >         Notification that this seat's keyboard focus is no longer on
> > -       a certain surface.
> > +       a certain surface.  The surface parameter may be null if the
> > +       surface has been destroyed.
> >
> >         The leave notification is sent before the enter notification
> >         for the new focus.
> >        </description>
> >        <arg name="serial" type="uint"/>
> > -      <arg name="surface" type="object" interface="wl_surface"/>
> > +      <arg name="surface" type="object" interface="wl_surface" allow-null="true"/>
> >      </event>
> >
> >      <enum name="key_state">
> > --
> > 1.8.1.4
> >
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