Politically correct terrible consequencer changes

This patch includes the work done in the terrible consequencer branch
that hasn't been merged to master minus a few controversial and WIP
stuff, like strip parenting, new sequence data structs and cuddly
widgets.

What is included:

* Strip extensions only when slipping. It can very easily be made an
option but with a few strips with overlapping durations it makes view
too crowded and difficult to make out.
* Threaded waveform loading + code that restores waveforms on undo (not
used though, since sound_load recreates everything. There's a patch for
review D876)
* Toggle to enable backdrop in the strip sequence editor
* Toggle to easily turn on/off waveform display
* Snapping during transform on sequence boundaries. Snapping to start or
end of selection depends on position of mouse when invoking the operator
* Snapping of timeline indicator in sequencer to strip boundaries. To
use just press and hold ctrl while dragging.

Reviewers: campbellbarton

Differential Revision: https://developer.blender.org/D904

1 files changed, 4 insertions, 3 deletions

diff --git a/source/blender/makesdna/DNA_sequence_types.h b/source/blender/makesdna/DNA_sequence_types.h
index af33ae80ed9..a7288b95a7a 100644
--- a/source/blender/makesdna/DNA_sequence_types.h
+++ b/source/blender/makesdna/DNA_sequence_types.h
@@ -131,10 +131,11 @@ typedef struct Sequence {
 
 	int flag, type; /*flags bitmap (see below) and the type of sequence*/
 	int len; /* the length of the contents of this strip - before handles are applied */
-	int start, startofs, endofs;
-	int startstill, endstill;
+	int start; /* start frame of contents of strip in absolute frame coordinates. For metastrips start of first strip startdisp */
+	int startofs, endofs; /* frames after the first frame where display starts, frames before the last frame where display ends */
+	int startstill, endstill; /* frames that use the first frame before data begins, frames that use the last frame after data ends */
 	int machine, depth; /*machine - the strip channel, depth - the depth in the sequence when dealing with metastrips */
-	int startdisp, enddisp; /*starting and ending points in the sequence*/
+	int startdisp, enddisp; /* starting and ending points of the strip in the sequence*/
 	float sat;
 	float mul, handsize;