Alembic: integrate cache file into the dependency graph

* The cache file datablock is now evaluated as part of the dependency graph,
  creating/freeing the Alembic file handle matching the current frame.
  Modifiers and constraints depend on this evaluation.
* Cache file handles and readers now only exist on COW datablocks, never the
  original ones.
* Object data paths are flushed back to the original for the user interface.
* The cache file keeps a list of all readers associated with its handle, and
  automatically frees them when the handle is freed. This kind of sharing of
  data across datablocks is weak but we have no better mechanism for it.

Fix T62720: Alembic sequences not working and crashing

Differential Revision: https://developer.blender.org/D4774

1 files changed, 8 insertions, 4 deletions

diff --git a/source/blender/makesdna/DNA_cachefile_types.h b/source/blender/makesdna/DNA_cachefile_types.h
index e5f77f70720..bc57202367c 100644
--- a/source/blender/makesdna/DNA_cachefile_types.h
+++ b/source/blender/makesdna/DNA_cachefile_types.h
@@ -30,10 +30,12 @@
 extern "C" {
 #endif
 
+struct GSet;
+
 /* CacheFile::flag */
 enum {
   CACHEFILE_DS_EXPAND = (1 << 0),
-  CACHEFILE_DIRTY = (1 << 1),
+  CACHEFILE_UNUSED_0 = (1 << 1),
 };
 
 /* CacheFile::draw_flag */
@@ -53,9 +55,6 @@ typedef struct CacheFile {
   ID id;
   struct AnimData *adt;
 
-  struct AbcArchiveHandle *handle;
-  void *handle_mutex;
-
   /** Paths of the objects inside of the Alembic archive referenced by this CacheFile. */
   ListBase object_paths;
 
@@ -78,6 +77,11 @@ typedef struct CacheFile {
   short draw_flag;
 
   char _pad[4];
+
+  /* Runtime */
+  struct AbcArchiveHandle *handle;
+  char handle_filepath[1024];
+  struct GSet *handle_readers;
 } CacheFile;
 
 #ifdef __cplusplus