[Bf-blender-cvs] [2a78504d0c1] blender-v2.83-release: Fix T78042: GPencil: Strokes go missing after Interpolation from another layer

[Antonio Vazquez]

Commit: 2a78504d0c18ea3105e69be9a2ed92a21961993b
Author: Antonio Vazquez
Date:   Fri Jun 19 19:39:21 2020 +0200
Branches: blender-v2.83-release
https://developer.blender.org/rB2a78504d0c18ea3105e69be9a2ed92a21961993b

Fix T78042: GPencil: Strokes go missing after Interpolation from another layer

This was due some strokes could be tagged and as the layer was locked, the strokes were not untagged and removed when all tagged strokes are removed.

The tagged strokes are used as temp ghost of the interpolation and removed at the end of the interpolation.

===================================================================

M	source/blender/editors/gpencil/gpencil_interpolate.c

===================================================================

diff --git a/source/blender/editors/gpencil/gpencil_interpolate.c b/source/blender/editors/gpencil/gpencil_interpolate.c
index 5cb49600d05..4ddcc60fb92 100644
--- a/source/blender/editors/gpencil/gpencil_interpolate.c
+++ b/source/blender/editors/gpencil/gpencil_interpolate.c
@@ -138,7 +138,9 @@ static void gp_interpolate_free_temp_strokes(bGPDframe *gpf)
 /* Helper: Untag all strokes. */
 static void gp_interpolate_untag_strokes(bGPDframe *gpf)
 {
-  BLI_assert(gpf != NULL);
+  if (gpf == NULL) {
+    return;
+  }
 
   LISTBASE_FOREACH (bGPDstroke *, gps, &gpf->strokes) {
     if (gps->flag & GP_STROKE_TAG) {
@@ -262,6 +264,12 @@ static void gp_interpolate_set_points(bContext *C, tGPDinterpolate *tgpi)
   LISTBASE_FOREACH (bGPDlayer *, gpl, &gpd->layers) {
     tGPDinterpolate_layer *tgpil;
 
+    /* Untag strokes to be sure nothing is pending. This must be done for
+     * all layer because it could be anything tagged and it would be removed
+     * at the end of the process when all tagged strokes are removed. */
+    gp_interpolate_untag_strokes(gpl->actframe);
+    gp_interpolate_untag_strokes(gpl->actframe->next);
+
     /* all layers or only active */
     if (!(tgpi->flag & GP_TOOLFLAG_INTERPOLATE_ALL_LAYERS) && (gpl != active_gpl)) {
       continue;
@@ -278,10 +286,6 @@ static void gp_interpolate_set_points(bContext *C, tGPDinterpolate *tgpi)
     tgpil->prevFrame = gpl->actframe;
     tgpil->nextFrame = gpl->actframe->next;
 
-    /* Untag interpolated strokes to be sure nothing is pending. */
-    gp_interpolate_untag_strokes(tgpil->prevFrame);
-    gp_interpolate_untag_strokes(tgpil->nextFrame);
-
     BLI_addtail(&tgpi->ilayers, tgpil);
 
     /* create a new temporary frame */