[Spice-devel] [spice-gtk v1] gtk-session: Use GWeakRef

[Christophe Fergeau]

On Mon, Feb 20, 2017 at 03:49:02PM +0100, Victor Toso wrote:
> From: Victor Toso <me at victortoso.com>
> 
> The custom WeakRef structure was introduced in 9baba9fd89 (2012) to
> fix rhbz#743773. Since glib 2.32, GWeakRef was introduced and it
> behaves similarly to our WeakRef.
> 
> Moving to GWeakRef to remove some code which exists in glib.
> 
> Note that I'm keeping to utility functions:
> - get_weak_ref(gpointer object): which returns a newly allocated
>   GWeakRef, initialized with @object;
> - free_weak_ref(gpointer pdata): which frees the GWeakRef and returns
>   the original object or NULL. It also takes care of an extra
>   reference to the object.

Yes, this dropping of the strong ref is a bit odd at first, but in the
end it's no different than how the code was working before, we expect
the object to stay alive for the duration of the callback if it was
alive when entering in the callback.

> 
> Signed-off-by: Victor Toso <victortoso at redhat.com>
> ---
>  src/spice-gtk-session.c | 52 +++++++++++++++++++------------------------------
>  1 file changed, 20 insertions(+), 32 deletions(-)
> 
> diff --git a/src/spice-gtk-session.c b/src/spice-gtk-session.c
> index 5688cba..88f4488 100644
> --- a/src/spice-gtk-session.c
> +++ b/src/spice-gtk-session.c
> @@ -575,31 +575,26 @@ static const struct {
>      }
>  };
>  
> -typedef struct _WeakRef {
> -    GObject *object;
> -} WeakRef;
> -
> -static void weak_notify_cb(WeakRef *weakref, GObject *object)
> -{
> -    weakref->object = NULL;
> -}
> -
> -static WeakRef* weak_ref(GObject *object)
> +static GWeakRef* get_weak_ref(gpointer object)
>  {
> -    WeakRef *weakref = g_new(WeakRef, 1);
> -
> -    g_object_weak_ref(object, (GWeakNotify)weak_notify_cb, weakref);
> -    weakref->object = object;
> -
> +    GWeakRef *weakref = g_new(GWeakRef, 1);
> +    g_weak_ref_init(weakref, object);
>      return weakref;
>  }
>  
> -static void weak_unref(WeakRef* weakref)
> +static gpointer free_weak_ref(gpointer data)
>  {
> -    if (weakref->object)
> -        g_object_weak_unref(weakref->object, (GWeakNotify)weak_notify_cb, weakref);
> +    GWeakRef *weakref = data;
> +    gpointer object = g_weak_ref_get(weakref);
>  
> +    g_weak_ref_clear(weakref);
>      g_free(weakref);
> +    if (object != NULL) {
> +        /* The main referece still exists as object is not NULL, so we can

'reference'

Looks good to me, though I'd probably return a ref to the callers, and
add a g_object_unref() to the end of the callbacks.

Acked-by: Christophe Fergeau <cfergeau at redhat.com>
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