From 20b6f7abb2f7698460c73809fcdcece1e848f176 Mon Sep 17 00:00:00 2001
From: Campbell Barton <ideasman42@gmail.com>
Date: Wed, 5 May 2021 17:57:32 +1000
Subject: Fix PlayAnim error applying cache limiter

Each frame display would add an item to the cache limiting list
without checking if it was already in the list.

Limiting would then free image buffers when the length of the list
exceeded USE_FRAME_CACHE_LIMIT (currently 30).

In practice this meant short animations would free and reload
frames during playback.
---
 source/blender/windowmanager/intern/wm_playanim.c | 27 +++++++++++++++++------
 1 file changed, 20 insertions(+), 7 deletions(-)

(limited to 'source')

diff --git a/source/blender/windowmanager/intern/wm_playanim.c b/source/blender/windowmanager/intern/wm_playanim.c
index 2dda3e3019a..96eeca18b24 100644
--- a/source/blender/windowmanager/intern/wm_playanim.c
+++ b/source/blender/windowmanager/intern/wm_playanim.c
@@ -237,6 +237,11 @@ typedef struct PlayAnimPict {
   struct anim *anim;
   int frame;
   int IB_flags;
+
+#ifdef USE_FRAME_CACHE_LIMIT
+  /** Back pointer to the #LinkData node for this struct in the #inmempicsbase list. */
+  LinkData *frame_cache_node;
+#endif
 } PlayAnimPict;
 
 static struct ListBase picsbase = {NULL, NULL};
@@ -1412,25 +1417,30 @@ static char *wm_main_playanim_intern(int argc, const char **argv)
       }
 
       if (ibuf) {
-#ifdef USE_FRAME_CACHE_LIMIT
-        LinkData *node;
-#endif
-
 #ifdef USE_IMB_CACHE
         ps.picture->ibuf = ibuf;
 #endif
 
 #ifdef USE_FRAME_CACHE_LIMIT
+        /* Don't free the current frame by moving it to the head of the list. */
+        if (ps.picture->frame_cache_node != NULL) {
+          BLI_assert(ps.picture->frame_cache_node->data == ps.picture);
+          BLI_remlink(&inmempicsbase, ps.picture->frame_cache_node);
+          BLI_addhead(&inmempicsbase, ps.picture->frame_cache_node);
+        }
+
         /* Really basic memory conservation scheme. Keep frames in a FIFO queue. */
-        node = inmempicsbase.last;
+        LinkData *node = inmempicsbase.last;
 
         while (node && added_images > PLAY_FRAME_CACHE_MAX) {
           PlayAnimPict *pic = node->data;
+          BLI_assert(pic->frame_cache_node == node);
 
           if (pic->ibuf && pic->ibuf != ibuf) {
             LinkData *node_tmp;
             IMB_freeImBuf(pic->ibuf);
             pic->ibuf = NULL;
+            pic->frame_cache_node = NULL;
             node_tmp = node->prev;
             BLI_freelinkN(&inmempicsbase, node);
             added_images--;
@@ -1441,8 +1451,11 @@ static char *wm_main_playanim_intern(int argc, const char **argv)
           }
         }
 
-        BLI_addhead(&inmempicsbase, BLI_genericNodeN(ps.picture));
-        added_images++;
+        if (ps.picture->frame_cache_node == NULL) {
+          ps.picture->frame_cache_node = BLI_genericNodeN(ps.picture);
+          BLI_addhead(&inmempicsbase, ps.picture->frame_cache_node);
+          added_images++;
+        }
 #endif /* USE_FRAME_CACHE_LIMIT */
 
         BLI_strncpy(ibuf->name, ps.picture->name, sizeof(ibuf->name));
-- 
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