Sequencer: Add session UUID management to Sequence

This is the first step for having sequences covered with session UUID
with the goal to remove code which uses original sequence pointer to
match sequences.

Currently this UUID is maintained on file load, allocation and leaf
duplication function.There are more cases to cover and ensure UUID
is re-generated or re-used when needed. It will be done as follow-up
development.

source/blender/blenkernel/BKE_sequencer.h

@@ -527,6 +527,9 @@ typedef struct Sequence *(*SeqLoadFn)(struct bContext *, ListBase *, struct SeqL
 
 struct Sequence *BKE_sequence_alloc(ListBase *lb, int cfra, int machine, int type);
 
+/* Generate new UUID for the given sequence. */
+void BKE_sequence_session_uuid_generate(struct Sequence *sequence);
+
 void BKE_sequence_alpha_mode_from_extension(struct Sequence *seq);
 void BKE_sequence_init_colorspace(struct Sequence *seq);
 

source/blender/blenkernel/intern/sequencer.c

@@ -46,6 +46,7 @@
 #include "BLI_listbase.h"
 #include "BLI_math.h"
 #include "BLI_path_util.h"
+#include "BLI_session_uuid.h"
 #include "BLI_string.h"
 #include "BLI_string_utf8.h"
 #include "BLI_threads.h"
@@ -5352,9 +5353,16 @@ Sequence *BKE_sequence_alloc(ListBase *lb, int cfra, int machine, int type)
   seq->stereo3d_format = MEM_callocN(sizeof(Stereo3dFormat), "Sequence Stereo Format");
   seq->cache_flag = SEQ_CACHE_STORE_RAW | SEQ_CACHE_STORE_PREPROCESSED | SEQ_CACHE_STORE_COMPOSITE;
 
+  BKE_sequence_session_uuid_generate(seq);
+
   return seq;
 }
 
+void BKE_sequence_session_uuid_generate(struct Sequence *sequence)
+{
+  sequence->runtime.session_uuid = BLI_session_uuid_generate();
+}
+
 void BKE_sequence_alpha_mode_from_extension(Sequence *seq)
 {
   if (seq->strip && seq->strip->stripdata) {
@@ -5664,6 +5672,10 @@ static Sequence *seq_dupli(const Scene *scene_src,
 {
   Sequence *seqn = MEM_dupallocN(seq);
 
+  if ((flag & LIB_ID_CREATE_NO_MAIN) == 0) {
+    BKE_sequence_session_uuid_generate(seq);
+  }
+
   seq->tmp = seqn;
   seqn->strip = MEM_dupallocN(seq->strip);
 

source/blender/blenloader/intern/readfile.c

@@ -6461,6 +6461,9 @@ static void direct_link_scene(BlendDataReader *reader, Scene *sce)
     link_recurs_seq(reader, &ed->seqbase);
 
     SEQ_BEGIN (ed, seq) {
+      /* Do as early as possible, so that other parts of reading can rely on valid session UUID. */
+      BKE_sequence_session_uuid_generate(seq);
+
       BLO_read_data_address(reader, &seq->seq1);
       BLO_read_data_address(reader, &seq->seq2);
       BLO_read_data_address(reader, &seq->seq3);