filter_chain: replace GetLength with IsEmpty

Nothing cares about the actual length if it is non-zero. Also constify.

include/vlc_filter.h

@@ -395,12 +395,12 @@ VLC_API void filter_chain_DeleteFilter(filter_chain_t *chain,
                                        filter_t *filter);
 
 /**
- * Get the number of filters in the filter chain.
+ * Checks if the filter chain is empty.
  *
  * \param chain pointer to filter chain
- * \return number of filters in this filter chain
+ * \return true if and only if there are no filters in this filter chain
  */
-VLC_API int filter_chain_GetLength(filter_chain_t *chain);
+VLC_API bool filter_chain_IsEmpty(const filter_chain_t *chain);
 
 /**
  * Get last output format of the last element in the filter chain.

modules/stream_out/transcode/video.c

@@ -706,7 +706,7 @@ static void OutputFrame( sout_stream_t *p_stream, picture_t *p_pic, sout_stream_
         /* Overlay subpicture */
         if( p_subpic )
         {
-            if( picture_IsReferenced( p_pic ) && !filter_chain_GetLength( id->p_f_chain ) )
+            if( picture_IsReferenced( p_pic ) && filter_chain_IsEmpty( id->p_f_chain ) )
             {
                 /* We can't modify the picture, we need to duplicate it,
                  * in this point the picture is already p_encoder->fmt.in format*/

src/libvlccore.sym

@@ -108,7 +108,7 @@ filter_chain_AppendFromString
 filter_chain_Delete
 filter_chain_DeleteFilter
 filter_chain_GetFmtOut
-filter_chain_GetLength
+filter_chain_IsEmpty
 filter_chain_MouseFilter
 filter_chain_MouseEvent
 filter_chain_NewVideo

src/misc/filter_chain.c

@@ -379,9 +379,9 @@ int filter_chain_ForEach( filter_chain_t *chain,
     return VLC_SUCCESS;
 }
 
-int filter_chain_GetLength( filter_chain_t *p_chain )
+bool filter_chain_IsEmpty(const filter_chain_t *chain)
 {
-    return p_chain->length;
+    return chain->length == 0;
 }
 
 const es_format_t *filter_chain_GetFmtOut( filter_chain_t *p_chain )

src/video_output/display.c

@@ -1093,7 +1093,7 @@ picture_t *vout_FilterDisplay(vout_display_t *vd, picture_t *picture)
     vout_display_owner_sys_t *osys = vd->owner.sys;
 
     assert(osys->filters);
-    if (filter_chain_GetLength(osys->filters) <= 0) {
+    if (filter_chain_IsEmpty(osys->filters)) {
         picture_Release(picture);
         return NULL;
     }

src/video_output/video_output.c

@@ -684,7 +684,7 @@ static picture_t *VoutVideoFilterStaticNewPicture(filter_t *filter)
     vout_thread_t *vout = filter->owner.sys;
 
     vlc_assert_locked(&vout->p->filter.lock);
-    if (filter_chain_GetLength(vout->p->filter.chain_interactive) == 0)
+    if (filter_chain_IsEmpty(vout->p->filter.chain_interactive))
         return VoutVideoFilterInteractiveNewPicture(filter);
 
     return picture_NewFromFormat(&filter->fmt_out.video);

src/video_output/vout_subpictures.c

@@ -1440,7 +1440,7 @@ void spu_PutSubpicture(spu_t *spu, subpicture_t *subpic)
         /* "sub-source"  was formerly "sub-filter", so now the "sub-filter"
         configuration may contain sub-filters or sub-sources configurations.
         if the filters chain was left empty it may indicate that it's a sub-source configuration */
-        is_left_empty = (filter_chain_GetLength(spu->p->filter_chain) == 0);
+        is_left_empty = filter_chain_IsEmpty(spu->p->filter_chain);
     }
     vlc_mutex_unlock(&sys->filter_chain_lock);