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

1 files changed, 4 insertions, 2 deletions

diff --git a/source/blender/sequencer/intern/strip_time.c b/source/blender/sequencer/intern/strip_time.c
index ec908dcdc93..06571b7ad43 100644
--- a/source/blender/sequencer/intern/strip_time.c
+++ b/source/blender/sequencer/intern/strip_time.c
@@ -20,6 +20,7 @@
 #include "DNA_sound_types.h"
 #include "IMB_imbuf.h"
 
+#include "SEQ_channels.h"
 #include "SEQ_iterator.h"
 #include "SEQ_render.h"
 #include "SEQ_sequencer.h"
@@ -321,6 +322,7 @@ int SEQ_time_find_next_prev_edit(Scene *scene,
                                  const bool do_unselected)
 {
   Editing *ed = SEQ_editing_get(scene);
+  ListBase *channels = SEQ_channels_displayed_get(ed);
   Sequence *seq;
 
   int dist, best_dist, best_frame = timeline_frame;
@@ -338,7 +340,7 @@ int SEQ_time_find_next_prev_edit(Scene *scene,
   for (seq = ed->seqbasep->first; seq; seq = seq->next) {
     int i;
 
-    if (do_skip_mute && (seq->flag & SEQ_MUTE)) {
+    if (do_skip_mute && SEQ_render_is_muted(channels, seq)) {
       continue;
     }
 
@@ -442,7 +444,7 @@ void SEQ_timeline_expand_boundbox(const ListBase *seqbase, rctf *rect)
     if (rect->xmax < seq->enddisp + 1) {
       rect->xmax = seq->enddisp + 1;
     }
-    if (rect->ymax < seq->machine + 2) {
+    if (rect->ymax < seq->machine) {
       rect->ymax = seq->machine + 2;
     }
   }