source/blender/blenkernel/intern/nla.c

@@ -812,7 +812,7 @@ void BKE_nlastrips_sort_strips(ListBase *strips)
 
     for (sstrip = tmp.last; sstrip; sstrip = sstrip->prev) {
       /* check if add after */
-      if (sstrip->end <= strip->start) {
+      if (sstrip->start <= strip->start) {
         BLI_insertlinkafter(&tmp, sstrip, strip);
         not_added = 0;
         break;
@@ -841,7 +841,7 @@ void BKE_nlastrips_add_strip_unsafe(ListBase *strips, NlaStrip *strip)
   /* find the right place to add the strip to the nominated track */
   for (ns = strips->first; ns; ns = ns->next) {
     /* if current strip occurs after the new strip, add it before */
-    if (ns->start >= strip->end) {
+    if (ns->start >= strip->start) {
       BLI_insertlinkbefore(strips, ns, strip);
       not_added = 0;
       break;
@@ -1962,6 +1962,24 @@ void BKE_nla_validate_state(AnimData *adt)
     return;
   }
 
+  /* Ensure every transition's start/end properly set. */
+  LISTBASE_FOREACH_MUTABLE (NlaTrack *, track, &adt->nla_tracks) {
+    LISTBASE_FOREACH_MUTABLE (NlaStrip *, strip, &track->strips) {
+      if (!(strip->type & NLASTRIP_TYPE_TRANSITION)) {
+        continue;
+      }
+      if (strip->prev) {
+        strip->start = strip->prev->end;
+      }
+      if (strip->next) {
+        strip->end = strip->next->start;
+      }
+      if (strip->start >= strip->end || strip->prev == NULL || strip->next == NULL) {
+        BKE_nlastrip_free(strip, true);
+      }
+    }
+  }
+
   /* Adjust blending values for auto-blending,
    * and also do an initial pass to find the earliest strip. */
   for (nlt = adt->nla_tracks.first; nlt; nlt = nlt->next) {

source/blender/editors/space_nla/nla_draw.c

@@ -485,7 +485,8 @@ static void nla_draw_strip(SpaceNla *snla,
   }
 
   /* draw 'inside' of strip itself */
-  if (non_solo == 0 && is_nlastrip_enabled(adt, nlt, strip)) {
+  if (non_solo == 0 && is_nlastrip_enabled(adt, nlt, strip) &&
+      !(strip->flag & NLASTRIP_FLAG_INVALID_LOCATION)) {
     immUnbindProgram();
 
     /* strip is in normal track */
@@ -532,13 +533,17 @@ static void nla_draw_strip(SpaceNla *snla,
   /* draw strip outline
    * - color used here is to indicate active vs non-active
    */
-  if (strip->flag & (NLASTRIP_FLAG_ACTIVE | NLASTRIP_FLAG_SELECT)) {
+  if (strip->flag & NLASTRIP_FLAG_INVALID_LOCATION) {
+    color[0] = 1.0f;
+    color[1] = color[2] = 0.15f;
+  }
+  else if (strip->flag & NLASTRIP_FLAG_ACTIVE) {
     /* strip should appear 'sunken', so draw a light border around it */
-    color[0] = color[1] = color[2] = 1.0f; /* FIXME: hardcoded temp-hack colors */
+    color[0] = color[1] = color[2] = 0.0f; /* FIXME: hardcoded temp-hack colors */
   }
   else {
     /* strip should appear to stand out, so draw a dark border around it */
-    color[0] = color[1] = color[2] = 0.0f; /* FIXME: or 1.0f ?? */
+    color[0] = color[1] = color[2] = 1.0f; /* FIXME: or 1.0f ?? */
   }
 
   /* draw outline

source/blender/makesdna/DNA_anim_types.h

@@ -832,6 +832,11 @@ typedef enum eNlaStrip_Flag {
   /* NLASTRIP_FLAG_MIRROR = (1 << 13), */ /* UNUSED */
 
   /* temporary editing flags */
+
+ /** When transforming strips, this flag is set when the strip is placed in an invalid location
+	* such as overlapping another strip or moved to a locked track. In such cases, the strip's
+	* location must be fixed. */
+  NLASTRIP_FLAG_INVALID_LOCATION = (1 << 28),
   /** NLA strip should ignore frame range and hold settings, and evaluate at global time. */
   NLASTRIP_FLAG_NO_TIME_MAP = (1 << 29),
   /** NLA-Strip is really just a temporary meta used to facilitate easier transform code */