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

4 files changed, 96 insertions, 13 deletions

diff --git a/source/blender/editors/transform/transform.c b/source/blender/editors/transform/transform.c
index ca971281420..7e27c11ec8a 100644
--- a/source/blender/editors/transform/transform.c
+++ b/source/blender/editors/transform/transform.c
@@ -7126,10 +7126,11 @@ static void headerSeqSlide(TransInfo *t, float val[2], char str[MAX_INFO_LEN])
 	                    WM_bool_as_string((t->flag & T_ALT_TRANSFORM) != 0));
 }
 
-static void applySeqSlideValue(TransInfo *t, const float val[2])
+static void applySeqSlideValue(TransInfo *t, const float val[2], int frame)
 {
 	TransData *td = t->data;
 	int i;
+	TransSeq *ts = t->customData;
 
 	for (i = 0; i < t->total; i++, td++) {
 		float tvec[2];
@@ -7144,15 +7145,21 @@ static void applySeqSlideValue(TransInfo *t, const float val[2])
 
 		mul_v2_fl(tvec, td->factor);
 
-		td->loc[0] = td->iloc[0] + tvec[0];
+		if (t->modifiers & MOD_SNAP_INVERT) {
+			td->loc[0] = frame + td->factor * (td->iloc[0] - ts->min);
+		}
+		else {
+			td->loc[0] = td->iloc[0] + tvec[0];
+		}
+
 		td->loc[1] = td->iloc[1] + tvec[1];
 	}
 }
 
-static void applySeqSlide(TransInfo *t, const int UNUSED(mval[2]))
+static void applySeqSlide(TransInfo *t, const int mval[2])
 {
 	char str[MAX_INFO_LEN];
-
+	int snap_frame = 0;
 	if (t->con.mode & CON_APPLY) {
 		float pvec[3] = {0.0f, 0.0f, 0.0f};
 		float tvec[3];
@@ -7160,7 +7167,8 @@ static void applySeqSlide(TransInfo *t, const int UNUSED(mval[2]))
 		copy_v3_v3(t->values, tvec);
 	}
 	else {
-		snapGridIncrement(t, t->values);
+		snap_frame = snapSequenceBounds(t, mval);
+		// snapGridIncrement(t, t->values);
 		applyNumInput(&t->num, t->values);
 	}
 
@@ -7168,7 +7176,7 @@ static void applySeqSlide(TransInfo *t, const int UNUSED(mval[2]))
 	t->values[1] = floor(t->values[1] + 0.5f);
 
 	headerSeqSlide(t, t->values, str);
-	applySeqSlideValue(t, t->values);
+	applySeqSlideValue(t, t->values, snap_frame);
 
 	recalcData(t);
 
diff --git a/source/blender/editors/transform/transform.h b/source/blender/editors/transform/transform.h
index 67d55639528..c2891b50321 100644
--- a/source/blender/editors/transform/transform.h
+++ b/source/blender/editors/transform/transform.h
@@ -173,6 +173,13 @@ typedef struct TransDataSeq {
 
 } TransDataSeq;
 
+typedef struct TransSeq {
+	TransDataSeq *tdseq;
+	int min;
+	int max;
+	bool snap_left;
+} TransSeq;
+
 /* for NLA transform (stored in td->extra pointer) */
 typedef struct TransDataNla {
 	ID *id;						/* ID-block NLA-data is attached to */
@@ -588,6 +595,8 @@ typedef enum {
 void snapGridIncrement(TransInfo *t, float *val);
 void snapGridIncrementAction(TransInfo *t, float *val, GearsType action);
 
+int snapSequenceBounds(TransInfo *t, const int mval[2]);
+
 bool activeSnap(TransInfo *t);
 bool validSnap(TransInfo *t);
 
diff --git a/source/blender/editors/transform/transform_conversions.c b/source/blender/editors/transform/transform_conversions.c
index e16a7155fe6..4d70768cfaa 100644
--- a/source/blender/editors/transform/transform_conversions.c
+++ b/source/blender/editors/transform/transform_conversions.c
@@ -4528,10 +4528,47 @@ static int SeqToTransData_Recursive(TransInfo *t, ListBase *seqbase, TransData *
 			}
 		}
 	}
-
 	return tot;
 }
 
+
+static void SeqTransDataBounds(TransInfo *t, ListBase *seqbase, TransSeq *ts)
+{
+	Sequence *seq;
+	int recursive, count, flag;
+	int max = INT32_MIN, min = INT32_MAX;
+
+	for (seq = seqbase->first; seq; seq = seq->next) {
+
+		/* just to get the flag since there are corner cases where this isn't totally obvious */
+		SeqTransInfo(t, seq, &recursive, &count, &flag);
+
+		/* use 'flag' which is derived from seq->flag but modified for special cases */
+		if (flag & SELECT) {
+			if (flag & (SEQ_LEFTSEL | SEQ_RIGHTSEL)) {
+				if (flag & SEQ_LEFTSEL) {
+					min = min_ii(seq->startdisp, min);
+					max = max_ii(seq->startdisp, max);
+				}
+				if (flag & SEQ_RIGHTSEL) {
+					min = min_ii(seq->enddisp, min);
+					max = max_ii(seq->enddisp, max);
+				}
+			}
+			else {
+				min = min_ii(seq->startdisp, min);
+				max = max_ii(seq->enddisp, max);
+			}
+		}
+	}
+
+	if (ts) {
+		ts->max = max;
+		ts->min = min;
+	}
+}
+
+
 static void freeSeqData(TransInfo *t)
 {
 	Editing *ed = BKE_sequencer_editing_get(t->scene, false);
@@ -4694,6 +4731,8 @@ static void freeSeqData(TransInfo *t)
 	}
 
 	if ((t->customData != NULL) && (t->flag & T_FREE_CUSTOMDATA)) {
+		TransSeq *ts = t->customData;
+		MEM_freeN(ts->tdseq);
 		MEM_freeN(t->customData);
 		t->customData = NULL;
 	}
@@ -4713,6 +4752,8 @@ static void createTransSeqData(bContext *C, TransInfo *t)
 	TransData *td = NULL;
 	TransData2D *td2d = NULL;
 	TransDataSeq *tdsq = NULL;
+	TransSeq *ts = NULL;
+	float xmouse, ymouse;
 
 	int count = 0;
 
@@ -4723,12 +4764,11 @@ static void createTransSeqData(bContext *C, TransInfo *t)
 
 	t->customFree = freeSeqData;
 
+	UI_view2d_region_to_view(v2d, t->imval[0], t->imval[1], &xmouse, &ymouse);
+
 	/* which side of the current frame should be allowed */
 	if (t->mode == TFM_TIME_EXTEND) {
 		/* only side on which mouse is gets transformed */
-		float xmouse, ymouse;
-
-		UI_view2d_region_to_view(v2d, t->imval[0], t->imval[1], &xmouse, &ymouse);
 		t->frame_side = (xmouse > CFRA) ? 'R' : 'L';
 	}
 	else {
@@ -4768,15 +4808,19 @@ static void createTransSeqData(bContext *C, TransInfo *t)
 		return;
 	}
 
+	t->customData = ts = MEM_mallocN(sizeof(TransSeq), "transseq");
 	td = t->data = MEM_callocN(t->total * sizeof(TransData), "TransSeq TransData");
 	td2d = t->data2d = MEM_callocN(t->total * sizeof(TransData2D), "TransSeq TransData2D");
-	tdsq = t->customData = MEM_callocN(t->total * sizeof(TransDataSeq), "TransSeq TransDataSeq");
+	ts->tdseq = tdsq = MEM_callocN(t->total * sizeof(TransDataSeq), "TransSeq TransDataSeq");
 	t->flag |= T_FREE_CUSTOMDATA;
 
-
-
 	/* loop 2: build transdata array */
 	SeqToTransData_Recursive(t, ed->seqbasep, td, td2d, tdsq);
+	SeqTransDataBounds(t, ed->seqbasep, ts);
+	
+	/* set the snap mode based on how close the mouse is at the end/start points */
+	if (abs(xmouse - ts->max) > abs(xmouse - ts->min))
+		ts->snap_left = true;
 
 #undef XXX_DURIAN_ANIM_TX_HACK
 }
diff --git a/source/blender/editors/transform/transform_snap.c b/source/blender/editors/transform/transform_snap.c
index 92c9c55ac64..4a2927ace00 100644
--- a/source/blender/editors/transform/transform_snap.c
+++ b/source/blender/editors/transform/transform_snap.c
@@ -59,6 +59,7 @@
 #include "BKE_anim.h"  /* for duplis */
 #include "BKE_context.h"
 #include "BKE_editmesh.h"
+#include "BKE_sequencer.h"
 #include "BKE_main.h"
 #include "BKE_tracking.h"
 
@@ -2430,6 +2431,27 @@ void snapGridIncrement(TransInfo *t, float *val)
 	snapGridIncrementAction(t, val, action);
 }
 
+int snapSequenceBounds(TransInfo *t, const int mval[2])
+{
+	float xmouse, ymouse;
+	int frame;
+	int mframe;
+	TransSeq *ts = t->customData;
+	/* reuse increment, strictly speaking could be another snap mode, but leave as is */
+	if (!(t->modifiers & MOD_SNAP_INVERT))
+		return 0;
+
+	/* convert to frame range */
+	UI_view2d_region_to_view(&t->ar->v2d, mval[0], mval[1], &xmouse, &ymouse);
+	mframe = iroundf(xmouse);
+	/* now find the closest sequence */
+	frame = BKE_sequencer_find_next_prev_edit(t->scene, mframe, SEQ_SIDE_BOTH, true, false, true);
+
+	if (!ts->snap_left)
+		frame = frame - (ts->max - ts->min);
+
+	return frame;
+}
 
 static void applyGridIncrement(TransInfo *t, float *val, int max_index, const float fac[3], GearsType action)
 {