m_option, vf: add label support

Can be used to refer to filters by name. Intended to be used when the
filter chain is changed at runtime.

A label can be assigned to a filter by prefixing it with '@name:', where
'name' is an user-chosen identifier. For example, a filter added with
'-vf-add @label1:gradfun=123' can be removed with '-vf-del @label1'.
If a filter with an already existing label is added, the existing filter
is replaced with the new filter (this happens for both -vf-add and
-vf-pre). If a filter is replaced, the new filter takes the position of
the old filter, instead of being appended/prepended to the filter chain
as usual. For -vf-toggle, labels are compared if at least one of the
filters has a label; otherwise they are compared by filter name and
arguments (like before). This means two filters are never considered
equal if one has a label and the other one does not.

1 files changed, 4 insertions, 0 deletions

diff --git a/video/filter/vf.h b/video/filter/vf.h
index 3ff4b5ea87..fd0118e152 100644
--- a/video/filter/vf.h
+++ b/video/filter/vf.h
@@ -66,6 +66,8 @@ typedef struct vf_instance {
 
     void (*uninit)(struct vf_instance *vf);
 
+    char *label;
+
     // data:
     struct vf_format fmt_in, fmt_out;
     struct vf_instance *next;
@@ -133,6 +135,8 @@ struct m_obj_settings;
 vf_instance_t *append_filters(vf_instance_t *last,
                               struct m_obj_settings *vf_settings);
 
+vf_instance_t *vf_find_by_label(vf_instance_t *chain, const char *label);
+
 void vf_uninit_filter(vf_instance_t *vf);
 void vf_uninit_filter_chain(vf_instance_t *vf);