Fix T87173: wrong Auto-Snap in animation editors

This was partially broken with {rBde9ea94fc6f}.

The `Frame Step` and `Second Step` snapping options were working as if
they were `Nearest Frame` and `Nearest Second` respectively in the
`Dope Sheet` and `NLA` editors.

In the `Graph Editor` the problem was more serious:
"Second Step: ... The keyframe itself moves along as though in snapping
were active at all, while its handles 'stay behind' until it reaches
the next second boundary, at which point the teleport handles to
'catch up'".

The snapping code for these modes was spread across the transform
mode code and `recalcData` of each data type. Therefore, create a
unified snapping code for these options so that all issues are fixed in
one place.

Differetial Revision: https://developer.blender.org/D12241

1 files changed, 38 insertions, 35 deletions

diff --git a/source/blender/editors/transform/transform_snap_animation.c b/source/blender/editors/transform/transform_snap_animation.c
index ac7c47e408f..be7fc65a6c2 100644
--- a/source/blender/editors/transform/transform_snap_animation.c
+++ b/source/blender/editors/transform/transform_snap_animation.c
@@ -90,67 +90,70 @@ short getAnimEdit_SnapMode(TransInfo *t)
 
 void snapFrameTransform(TransInfo *t,
                         const eAnimEdit_AutoSnap autosnap,
-                        const bool is_frame_value,
-                        const float delta,
-                        /* return args */
-                        float *r_val)
+                        const float val_initial,
+                        const float val_final,
+                        float *r_val_final)
 {
-  double val = delta;
+  float deltax = val_final - val_initial;
   switch (autosnap) {
-    case SACTSNAP_STEP:
     case SACTSNAP_FRAME:
-      val = floor(val + 0.5);
+      *r_val_final = floorf(val_final + 0.5f);
       break;
     case SACTSNAP_MARKER:
-      /* snap to nearest marker */
+      /* Snap to nearest marker. */
       /* TODO: need some more careful checks for where data comes from. */
-      val = ED_markers_find_nearest_marker_time(&t->scene->markers, (float)val);
+      *r_val_final = (float)ED_markers_find_nearest_marker_time(&t->scene->markers, val_final);
       break;
     case SACTSNAP_SECOND:
     case SACTSNAP_TSTEP: {
-      /* second step */
       const Scene *scene = t->scene;
       const double secf = FPS;
-      val = floor((val / secf) + 0.5);
-      if (is_frame_value) {
-        val *= secf;
+      if (autosnap == SACTSNAP_SECOND) {
+        *r_val_final = floorf((val_final / secf) + 0.5) * secf;
+      }
+      else {
+        deltax = (float)(floor((deltax / secf) + 0.5) * secf);
+        *r_val_final = val_initial + deltax;
       }
       break;
     }
-    case SACTSNAP_OFF: {
+    case SACTSNAP_STEP:
+      deltax = floorf(deltax + 0.5f);
+      *r_val_final = val_initial + deltax;
+      break;
+    case SACTSNAP_OFF:
       break;
-    }
   }
-  *r_val = (float)val;
 }
 
 /* This function is used by Animation Editor specific transform functions to do
  * the Snap Keyframe to Nearest Frame/Marker
  */
-void doAnimEdit_SnapFrame(
-    TransInfo *t, TransData *td, TransData2D *td2d, AnimData *adt, short autosnap)
+void transform_snap_anim_flush_data(TransInfo *t,
+                                    TransData *td,
+                                    const eAnimEdit_AutoSnap autosnap,
+                                    float *r_val_final)
 {
-  if (autosnap != SACTSNAP_OFF) {
-    float val;
+  BLI_assert(autosnap != SACTSNAP_OFF);
 
-    /* convert frame to nla-action time (if needed) */
-    if (adt && (t->spacetype != SPACE_SEQ)) {
-      val = BKE_nla_tweakedit_remap(adt, *(td->val), NLATIME_CONVERT_MAP);
-    }
-    else {
-      val = *(td->val);
-    }
+  float val = td->loc[0];
+  float ival = td->iloc[0];
+  AnimData *adt = (!ELEM(t->spacetype, SPACE_NLA, SPACE_SEQ)) ? td->extra : NULL;
 
-    snapFrameTransform(t, autosnap, true, val, &val);
+  /* Convert frame to nla-action time (if needed) */
+  if (adt) {
+    val = BKE_nla_tweakedit_remap(adt, val, NLATIME_CONVERT_MAP);
+    ival = BKE_nla_tweakedit_remap(adt, ival, NLATIME_CONVERT_MAP);
+  }
 
-    /* convert frame out of nla-action time */
-    if (adt && (t->spacetype != SPACE_SEQ)) {
-      *(td->val) = BKE_nla_tweakedit_remap(adt, val, NLATIME_CONVERT_UNMAP);
-    }
-    else {
-      *(td->val) = val;
-    }
+  snapFrameTransform(t, autosnap, ival, val, &val);
+
+  /* Convert frame out of nla-action time. */
+  if (adt) {
+    val = BKE_nla_tweakedit_remap(adt, val, NLATIME_CONVERT_UNMAP);
   }
+
+  *r_val_final = val;
 }
 
 /** \} */