[PATCH weston] input: Don't use uninitialized variables in default_grab_pointer_focus()

[Pekka Paalanen]

On Wed,  8 Apr 2015 15:18:41 -0500
Derek Foreman <derekf at osg.samsung.com> wrote:

> If we have no pointer focus and weston_compositor_pick_view() returns NULL
> default_grab_pointer_focus() will test the unset sx, sy output parameters
> from weston_compositor_pick_view().
> 
> Instead, assume that since both pointers are NULL focus hasn't changed and
> we don't need to update pointer focus.
> 
> Signed-off-by: Derek Foreman <derekf at osg.samsung.com>
> ---
> 
> This fixes an error reported by valgrind.  I think the patch is correct but
> it does stop pointer->focus_signal from being emitted when focus switches
> from NULL to NULL.  I think that shouldn't have happened anyway?

If focus switches from NULL to NULL, weston_pointer_set_focus() would
never be called because of the pointer->focus != view check, right?

So the case you saw in Valgrind must be a case of !NULL -> NULL switch,
which has to be processed but does not have valid sx, sy by definition.
Therefore...

> Initializing sx, sy to wl_fixed_from_int(0) would silence the warning too,
> but I think this way is more correct...

...isn't initializing the sx, sy the right thing to do, and this patch
actually fixes nothing?

Did I miss something?

>  src/input.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/src/input.c b/src/input.c
> index 142c670..18d1262 100644
> --- a/src/input.c
> +++ b/src/input.c
> @@ -157,6 +157,9 @@ default_grab_pointer_focus(struct weston_pointer_grab *grab)
>  					   pointer->x, pointer->y,
>  					   &sx, &sy);
>  
> +	if (!pointer->focus && !view)
> +		return;
> +
>  	if (pointer->focus != view || pointer->sx != sx || pointer->sy != sy)
>  		weston_pointer_set_focus(pointer, view, sx, sy);
>  }


Thanks,
pq