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, 2 insertions, 0 deletions

diff --git a/core/m_option.h b/core/m_option.h
index c94b170424..6a8bcfbf1a 100644
--- a/core/m_option.h
+++ b/core/m_option.h
@@ -110,6 +110,8 @@ typedef struct {
 typedef struct m_obj_settings {
     // Type of the object.
     char *name;
+    // Optional user-defined name.
+    char *label;
     // NULL terminated array of parameter/value pairs.
     char **attribs;
 } m_obj_settings_t;