WIP: Added dedicated operator for unlinking actions from the Action Editor (NLA buttons support to come)

After looking into this more carefully, I've found that we do in fact need a dedicate
operator to add some custom logic when trying to unlink an action from the editor/datablocks.

Specifically, this new operator does the following:
1) When in Tweak Mode, it shouldn't be possible to unlink the active action,
   or else, everything turns to custard.
2) If the Action doesn't have any other users, the user should at least get
   a warning that it is going to get lost.
3) We need a convenient way to exit Tweak Mode from the Action Editor
4) If none of the above apply, we can just unlink normally

This commit implements this for the Action Editor, with stubs for the NLA Editor too.
Those will be fixed next.

1 files changed, 46 insertions, 0 deletions

diff --git a/source/blender/editors/space_nla/nla_channels.c b/source/blender/editors/space_nla/nla_channels.c
index 5476d1c2683..70d9bfe99fe 100644
--- a/source/blender/editors/space_nla/nla_channels.c
+++ b/source/blender/editors/space_nla/nla_channels.c
@@ -504,6 +504,52 @@ void NLA_OT_action_pushdown(wmOperatorType *ot)
 	RNA_def_property_flag(ot->prop, PROP_SKIP_SAVE);
 }
 
+/* ******************** Action Unlink ******************************** */
+
+static int nla_action_unlink_poll(bContext *C)
+{
+	if (ED_operator_nla_active(C)) {
+		return nla_panel_context(C, NULL, NULL, NULL);
+	}
+	
+	/* something failed... */
+	return false;
+}
+
+static int nla_action_unlink_exec(bContext *C, wmOperator *op)
+{
+	PointerRNA adt_ptr;
+	AnimData *adt;
+	
+	/* check context and also validity of pointer */
+	if (!nla_panel_context(C, &adt_ptr, NULL, NULL))
+		return OPERATOR_CANCELLED;
+	
+	/* get animdata */
+	adt = adt_ptr.data;
+	if (adt == NULL)
+		return OPERATOR_CANCELLED;
+	
+	/* do unlinking */
+	if (adt && adt->action) {
+		ED_animedit_unlink_action(C, adt_ptr.id.data, adt, adt->action, op->reports);
+	}
+	
+	return OPERATOR_FINISHED;
+}
+
+void NLA_OT_action_unlink(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Unlink Action";
+	ot->idname = "NLA_OT_action_unlink";
+	ot->description = "Unlink this action from the active action slot (and/or exit Tweak Mode)";
+	
+	/* callbacks */
+	ot->exec = nla_action_unlink_exec;
+	ot->poll = nla_action_unlink_poll;
+}
+
 /* ******************** Add Tracks Operator ***************************** */
 /* Add NLA Tracks to the same AnimData block as a selected track, or above the selected tracks */