Add a mechanism for selective style overrides

This adds 2 new API functions:

  ass_set_selective_style_override()
  ass_set_selective_style_override_enabled()

They can be used to force dialog text to use a specific ASS_Style. It
uses a fuzzy heuristic for that, and the quality of results may vary.
It does style overriding selectively and tries not to override things
that need explicit styling. The heuristic for that isn't set in stone
either, and can change with future libass versions.

Closes libass#88.

1 files changed, 26 insertions, 0 deletions

diff --git a/libass/ass_parse.c b/libass/ass_parse.c
index d6b2627..d0d1972 100644
--- a/libass/ass_parse.c
+++ b/libass/ass_parse.c
@@ -1025,3 +1025,29 @@ unsigned get_next_char(ASS_Renderer *render_priv, char **str)
     *str = p;
     return chr;
 }
+
+// Return 1 if the event contains tags that will put the renderer into the
+// EVENT_POSITIONED state. Return 0 otherwise.
+int event_is_positioned(char *str)
+{
+    // look for \pos and \move tags inside {...}
+    // mirrors get_next_char, but is faster and doesn't change any global state
+    while (*str) {
+        if (str[0] == '\\' && str[1] != '\0') {
+            str += 2;
+        } else if (str[0] == '{') {
+            str++;
+            while (*str && *str != '}') {
+                if (*str == '\\') {
+                    char *p = str + 1;
+                    if (mystrcmp(&p, "pos") || mystrcmp(&p, "move"))
+                        return 1;
+                }
+                str++;
+            }
+        } else {
+            str++;
+        }
+    }
+    return 0;
+}