renderer: fix incorrect deallocation

shift_event() can change "bitmap" field of ASS_Image struct
so direct deallocation is no longer possible.
This commit introduces additional field "buffer"
into ASS_ImagePriv for that purpose.

Fixes https://github.com/libass/libass/issues/310.

1 files changed, 1 insertions, 0 deletions

diff --git a/libass/ass_render.h b/libass/ass_render.h
index e654a94..4558575 100644
--- a/libass/ass_render.h
+++ b/libass/ass_render.h
@@ -52,6 +52,7 @@
 typedef struct {
     ASS_Image result;
     CompositeHashValue *source;
+    unsigned char *buffer;
     size_t ref_count;
 } ASS_ImagePriv;