Cancel Equalize Handles & Snap Keys when no control points are selected

The Equalize Handles and Snap Keys operators would allow the user to
invoke them successfully even when they would have no effect due to
there not being any selected control points.

This patch makes it so that an error is displayed when these operators
are invoked with no control points are selected.

The reason this is in the `invoke` function is because it would be too
expensive to run this check in the `poll` function since it requires a
linear search through all the keys of all the visible F-Curves.

Reviewed By: sybren

Differential Revision: https://developer.blender.org/D16390

3 files changed, 61 insertions, 2 deletions

diff --git a/source/blender/blenkernel/BKE_fcurve.h b/source/blender/blenkernel/BKE_fcurve.h
index c11e6353bc0..cbdf37e14bd 100644
--- a/source/blender/blenkernel/BKE_fcurve.h
+++ b/source/blender/blenkernel/BKE_fcurve.h
@@ -431,6 +431,11 @@ bool BKE_fcurve_is_keyframable(struct FCurve *fcu);
 bool BKE_fcurve_is_protected(struct FCurve *fcu);
 
 /**
+ * Are any of the keyframe control points selected on the F-Curve?
+ */
+bool BKE_fcurve_has_selected_control_points(const struct FCurve *fcu);
+
+/**
  * Checks if the F-Curve has a Cycles modifier with simple settings
  * that warrant transition smoothing.
  */
diff --git a/source/blender/blenkernel/intern/fcurve.c b/source/blender/blenkernel/intern/fcurve.c
index beea3217126..d248faaab00 100644
--- a/source/blender/blenkernel/intern/fcurve.c
+++ b/source/blender/blenkernel/intern/fcurve.c
@@ -965,6 +965,18 @@ bool BKE_fcurve_is_protected(FCurve *fcu)
   return ((fcu->flag & FCURVE_PROTECTED) || ((fcu->grp) && (fcu->grp->flag & AGRP_PROTECTED)));
 }
 
+bool BKE_fcurve_has_selected_control_points(const FCurve *fcu)
+{
+  int i;
+  BezTriple *bezt;
+  for (bezt = fcu->bezt, i = 0; i < fcu->totvert; ++i, ++bezt) {
+    if ((bezt->f2 & SELECT) != 0) {
+      return true;
+    }
+  }
+  return false;
+}
+
 bool BKE_fcurve_is_keyframable(FCurve *fcu)
 {
   /* F-Curve's keyframes must be "usable" (i.e. visible + have an effect on final result) */
diff --git a/source/blender/editors/space_graph/graph_edit.c b/source/blender/editors/space_graph/graph_edit.c
index a23b33dde95..c605ba6776f 100644
--- a/source/blender/editors/space_graph/graph_edit.c
+++ b/source/blender/editors/space_graph/graph_edit.c
@@ -2333,6 +2333,48 @@ static int graphkeys_snap_exec(bContext *C, wmOperator *op)
   return OPERATOR_FINISHED;
 }
 
+bool graph_has_selected_control_points(struct bContext *C)
+{
+  bAnimContext ac;
+  ListBase anim_data = {NULL, NULL};
+
+  /* Get editor data. */
+  if (ANIM_animdata_get_context(C, &ac) == 0) {
+    return OPERATOR_CANCELLED;
+  }
+
+  /* Filter data. */
+  const int filter = (ANIMFILTER_DATA_VISIBLE | ANIMFILTER_CURVE_VISIBLE | ANIMFILTER_FCURVESONLY |
+                      ANIMFILTER_FOREDIT | ANIMFILTER_NODUPLIS);
+  ANIM_animdata_filter(&ac, &anim_data, filter, ac.data, ac.datatype);
+
+  /* Check if any of the visible and editable f-curves have at least one selected control point. */
+  bool has_selected_control_points = false;
+  LISTBASE_FOREACH (bAnimListElem *, ale, &anim_data) {
+    const FCurve *fcu = ale->key_data;
+    if (BKE_fcurve_has_selected_control_points(fcu)) {
+      has_selected_control_points = true;
+      break;
+    }
+  }
+
+  ANIM_animdata_freelist(&anim_data);
+
+  return has_selected_control_points;
+}
+
+int graphkeys_selected_control_points_invoke(struct bContext *C,
+                                             struct wmOperator *op,
+                                             const struct wmEvent *event)
+{
+  if (!graph_has_selected_control_points(C)) {
+    BKE_report(op->reports, RPT_ERROR, "No control points are selected");
+    return OPERATOR_CANCELLED;
+  }
+
+  return WM_menu_invoke(C, op, event);
+}
+
 void GRAPH_OT_snap(wmOperatorType *ot)
 {
   /* Identifiers */
@@ -2341,7 +2383,7 @@ void GRAPH_OT_snap(wmOperatorType *ot)
   ot->description = "Snap selected keyframes to the chosen times/values";
 
   /* API callbacks */
-  ot->invoke = WM_menu_invoke;
+  ot->invoke = graphkeys_selected_control_points_invoke;
   ot->exec = graphkeys_snap_exec;
   ot->poll = graphop_editable_keyframes_poll;
 
@@ -2418,7 +2460,7 @@ void GRAPH_OT_equalize_handles(wmOperatorType *ot)
       "Ensure selected keyframes' handles have equal length, optionally making them horizontal. "
       "Automatic, Automatic Clamped, or Vector handle types will be converted to Aligned";
   /* API callbacks */
-  ot->invoke = WM_menu_invoke;
+  ot->invoke = graphkeys_selected_control_points_invoke;
   ot->exec = graphkeys_equalize_handles_exec;
   ot->poll = graphop_editable_keyframes_poll;