Allow passing user data to callback

It is often useful or necessary to pass custom data to a callback.
Add an argument to the callback registering function to pass a void
pointer object to the callback each time it is called.

1 files changed, 1 insertions, 1 deletions

diff --git a/libass/ass_utils.c b/libass/ass_utils.c
index 0592d33e..56ca0ef6 100644
--- a/libass/ass_utils.c
+++ b/libass/ass_utils.c
@@ -126,7 +126,7 @@ void ass_msg(ass_library_t *priv, int lvl, char *fmt, ...)
 {
     va_list va;
     va_start(va, fmt);
-    priv->msg_callback(lvl, fmt, &va);
+    priv->msg_callback(lvl, fmt, &va, priv->msg_callback_data);
     va_end(va);
 }