options: pre-check filter names when using vf/af libavfilter bridge

Until now, using a filter not in mpv's builtin filter list would assume
it's a libavfilter filter. If it wasn't, the option value was still
accepted, but creating the filter simply failed. But since this happens
after option parsing, so the result is confusing.

Improve this slightly by checking filter names. This will reject truly
unknown filters at option parsing time. Unfortunately, this still does
not check filter arguments. This would be much more complex, because
you'd have to create a dummy filter graph and allocate the filter. Maybe
another time.

1 files changed, 3 insertions, 0 deletions

diff --git a/options/m_option.h b/options/m_option.h
index 4289fa5a2e..a5f9618462 100644
--- a/options/m_option.h
+++ b/options/m_option.h
@@ -149,6 +149,9 @@ struct m_obj_list {
     // Allow unknown entries, for which a dummy entry is inserted, and whose
     // options are skipped and ignored.
     bool allow_unknown_entries;
+    // Callback to test whether an unknown entry should be allowed. (This can
+    // be useful if adding them as explicit entries is too much work.)
+    bool (*check_unknown_entry)(const char *name);
     // Allow syntax for disabling entries.
     bool allow_disable_entries;
     // This helps with confusing error messages if unknown flag options are used.