VSE: Add channel headers

This patch adds channel region to VSE timeline area for drawing channel
headers. It is synchronizedwith timeline region. 3 basic features are
implemented - channel visibility, locking and name.

Channel data is stored in `SeqTimelineChannel` which can be top-level
owned by `Editing`, or it is owned by meta strip to support nesting.
Strip properties are completely independent and channel properties are
applied on top of particular strip property, thus overriding it.

Implementation is separate from channel regions in other editors. This
is mainly because style and topology is quite different in VSE. But
also code seems to be much more readable this way.

Currently channels use functions similar to VSE timeline to draw
background to provide illusion of transparency, but only for background
and sfra/efra regions.

Great portion of this patch is change from using strip visibility and
lock status to include channel state - this is facilitated by functions
`SEQ_transform_is_locked` and `SEQ_render_is_muted`

Originally this included changes in D14263, but patch was split for
easier review.

Reviewed By: fsiddi, Severin

Differential Revision: https://developer.blender.org/D13836

2 files changed, 54 insertions, 13 deletions

diff --git a/source/blender/blenkernel/BKE_blender_version.h b/source/blender/blenkernel/BKE_blender_version.h
index 604c8cb7a06..1f3b0606dfd 100644
--- a/source/blender/blenkernel/BKE_blender_version.h
+++ b/source/blender/blenkernel/BKE_blender_version.h
@@ -25,7 +25,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 8
+#define BLENDER_FILE_SUBVERSION 9
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and show a warning if the file
diff --git a/source/blender/blenkernel/intern/scene.cc b/source/blender/blenkernel/intern/scene.cc
index 685d24cee38..cc1204abbfb 100644
--- a/source/blender/blenkernel/intern/scene.cc
+++ b/source/blender/blenkernel/intern/scene.cc
@@ -321,6 +321,7 @@ static void scene_copy_data(Main *bmain, ID *id_dst, const ID *id_src, const int
                                       &scene_src->ed->seqbase,
                                       SEQ_DUPE_ALL,
                                       flag_subdata);
+    BLI_duplicatelist(&scene_dst->ed->channels, &scene_src->ed->channels);
   }
 
   if ((flag & LIB_ID_COPY_NO_PREVIEW) == 0) {
@@ -990,6 +991,9 @@ static void scene_blend_write(BlendWriter *writer, ID *id, const void *id_addres
     BLO_write_struct(writer, Editing, ed);
 
     SEQ_blend_write(writer, &ed->seqbase);
+    LISTBASE_FOREACH (SeqTimelineChannel *, channel, &ed->channels) {
+      BLO_write_struct(writer, SeqTimelineChannel, channel);
+    }
     /* new; meta stack too, even when its nasty restore code */
     LISTBASE_FOREACH (MetaStack *, ms, &ed->metastack) {
       BLO_write_struct(writer, MetaStack, ms);
@@ -1174,6 +1178,7 @@ static void scene_blend_read_data(BlendDataReader *reader, ID *id)
 
   if (sce->ed) {
     ListBase *old_seqbasep = &sce->ed->seqbase;
+    ListBase *old_displayed_channels = &sce->ed->channels;
 
     BLO_read_data_address(reader, &sce->ed);
     Editing *ed = sce->ed;
@@ -1188,32 +1193,53 @@ static void scene_blend_read_data(BlendDataReader *reader, ID *id)
 
     /* Read in sequence member data. */
     SEQ_blend_read(reader, &ed->seqbase);
+    BLO_read_list(reader, &ed->channels);
 
     /* link metastack, slight abuse of structs here,
      * have to restore pointer to internal part in struct */
     {
       Sequence temp;
-      void *poin;
-      intptr_t offset;
+      void *seqbase_poin;
+      void *channels_poin;
+      intptr_t seqbase_offset;
+      intptr_t channels_offset;
 
-      offset = ((intptr_t) & (temp.seqbase)) - ((intptr_t)&temp);
+      seqbase_offset = ((intptr_t) & (temp.seqbase)) - ((intptr_t)&temp);
+      channels_offset = ((intptr_t) & (temp.channels)) - ((intptr_t)&temp);
 
-      /* root pointer */
+      /* seqbase root pointer */
       if (ed->seqbasep == old_seqbasep) {
         ed->seqbasep = &ed->seqbase;
       }
       else {
-        poin = POINTER_OFFSET(ed->seqbasep, -offset);
+        seqbase_poin = POINTER_OFFSET(ed->seqbasep, -seqbase_offset);
 
-        poin = BLO_read_get_new_data_address(reader, poin);
+        seqbase_poin = BLO_read_get_new_data_address(reader, seqbase_poin);
 
-        if (poin) {
-          ed->seqbasep = (ListBase *)POINTER_OFFSET(poin, offset);
+        if (seqbase_poin) {
+          ed->seqbasep = (ListBase *)POINTER_OFFSET(seqbase_poin, seqbase_offset);
         }
         else {
           ed->seqbasep = &ed->seqbase;
         }
       }
+
+      /* Active channels root pointer. */
+      if (ed->displayed_channels == old_displayed_channels || ed->displayed_channels == NULL) {
+        ed->displayed_channels = &ed->channels;
+      }
+      else {
+        channels_poin = POINTER_OFFSET(ed->displayed_channels, -channels_offset);
+        channels_poin = BLO_read_get_new_data_address(reader, channels_poin);
+
+        if (channels_poin) {
+          ed->displayed_channels = (ListBase *)POINTER_OFFSET(channels_poin, channels_offset);
+        }
+        else {
+          ed->displayed_channels = &ed->channels;
+        }
+      }
+
       /* stack */
       BLO_read_list(reader, &(ed->metastack));
 
@@ -1224,15 +1250,30 @@ static void scene_blend_read_data(BlendDataReader *reader, ID *id)
           ms->oldbasep = &ed->seqbase;
         }
         else {
-          poin = POINTER_OFFSET(ms->oldbasep, -offset);
-          poin = BLO_read_get_new_data_address(reader, poin);
-          if (poin) {
-            ms->oldbasep = (ListBase *)POINTER_OFFSET(poin, offset);
+          seqbase_poin = POINTER_OFFSET(ms->oldbasep, -seqbase_offset);
+          seqbase_poin = BLO_read_get_new_data_address(reader, seqbase_poin);
+          if (seqbase_poin) {
+            ms->oldbasep = (ListBase *)POINTER_OFFSET(seqbase_poin, seqbase_offset);
           }
           else {
             ms->oldbasep = &ed->seqbase;
           }
         }
+
+        if (ms->old_channels == old_displayed_channels || ms->old_channels == NULL) {
+          ms->old_channels = &ed->channels;
+        }
+        else {
+          channels_poin = POINTER_OFFSET(ms->old_channels, -channels_offset);
+          channels_poin = BLO_read_get_new_data_address(reader, channels_poin);
+
+          if (channels_poin) {
+            ms->old_channels = (ListBase *)POINTER_OFFSET(channels_poin, channels_offset);
+          }
+          else {
+            ms->old_channels = &ed->channels;
+          }
+        }
       }
     }
   }