thumbnailer: notify on_ended when cancelled

Like the preparser is doing.

include/vlc_thumbnailer.h

@@ -45,9 +45,11 @@ struct vlc_thumbnailer_cbs
      *
      * @note This callback is mandatory.
      *
-     * In case of failure, p_thumbnail will be NULL.  The picture, if any, is
-     * owned by the thumbnailer, and must be acquired by using \link
-     * picture_Hold \endlink to use it pass the callback's scope.
+     * In case of failure, timeout or cancellation, p_thumbnail will be NULL.
+     * The picture, if any, is owned by the thumbnailer, and must be acquired
+     * by using \link picture_Hold \endlink to use it pass the callback's
+     * scope.
+     *
      * \param thumbnail The generated thumbnail, or NULL in case of failure or
      * timeout
      * \param data Is the opaque pointer passed as vlc_thumbnailer_Request last

src/input/thumbnailer.c

@@ -209,13 +209,12 @@ RunnableRun(void *userdata)
     picture_t* pic = task->pic;
     task->pic = NULL;
 
-    bool notify = task->status != INTERRUPTED;
+    bool interrupted = task->status == INTERRUPTED;
 
     vlc_list_remove(&task->node);
     vlc_mutex_unlock(&thumbnailer->lock);
 
-    if (notify)
-        NotifyThumbnail(task, pic);
+    NotifyThumbnail(task, interrupted ? NULL : pic);
 
     if (pic)
         picture_Release(pic);
@@ -268,7 +267,15 @@ size_t vlc_thumbnailer_Cancel( vlc_thumbnailer_t* thumbnailer, vlc_thumbnailer_r
             if (canceled)
             {
                 vlc_list_remove(&task->node);
+                vlc_mutex_unlock(&thumbnailer->lock);
+                NotifyThumbnail(task, NULL);
                 TaskDestroy(task);
+
+                /* Small optimisation in the likely case where the user cancel
+                 * only one task */
+                if (id != VLC_THUMBNAILER_REQ_ID_INVALID)
+                    return count;
+                vlc_mutex_lock(&thumbnailer->lock);
             }
             else
             {

test/src/input/thumbnail.c

@@ -173,9 +173,9 @@ static void test_thumbnails( libvlc_instance_t* p_vlc )
 
 static void thumbnailer_callback_cancel( picture_t* p_thumbnail, void *data )
 {
-    (void) data; (void) p_thumbnail;
+    (void) data;
     /* This callback should not be called since the request is cancelled */
-    vlc_assert_unreachable();
+    assert( p_thumbnail == NULL );
 }
 
 static void test_cancel_thumbnail( libvlc_instance_t* p_vlc )