From 4b5437157d4d0dc39137f076ea6dace80c4fadd8 Mon Sep 17 00:00:00 2001
From: Rodolfo Ribeiro Gomes <rodolforg@gmail.com>
Date: Dec 13 2019 04:29:26 +0000
Subject: fix bug when moving curve points in time


issue described here
https://github.com/synfig/synfig/pull/982#issuecomment-551694936

---

diff --git a/synfig-studio/src/gui/widgets/widget_curves.cpp b/synfig-studio/src/gui/widgets/widget_curves.cpp
index b81a9c7..8afd7d3 100644
--- a/synfig-studio/src/gui/widgets/widget_curves.cpp
+++ b/synfig-studio/src/gui/widgets/widget_curves.cpp
@@ -755,6 +755,9 @@ void Widget_Curves::delta_drag(int dx, int dy)
 	const Time deltatime = next_time - base_time;
 
 	if (deltatime != 0) {
+		auto waypoints_to_restore = saved_waypoints;
+		saved_waypoints.clear();
+
 		for (auto &point : selected_points) {
 			const ValueDesc &value_desc = point.curve_it->value_desc;
 			const Time &time = point.time_point.get_time();
@@ -762,12 +765,42 @@ void Widget_Curves::delta_drag(int dx, int dy)
 
 			std::pair<const ValueDesc&, Time> meta_data(value_desc, time);
 			if (times_to_move.find(meta_data) == times_to_move.end()) {
+				auto time_set = WaypointRenderer::get_times_from_valuedesc(value_desc);
+
+				// are we overlapping existing waypoints while moving in time?
+				auto new_timepoint = time_set.find(new_time);
+				if (new_timepoint != time_set.end()) {
+					std::set<synfig::Waypoint, std::less<UniqueID> > waypoint_set;
+					synfig::waypoint_collect(waypoint_set, new_time, value_desc.get_value_node());
+					for (const Waypoint &waypoint : waypoint_set) {
+						saved_waypoints.push_back(std::pair<Waypoint, std::list<CurveStruct>::iterator>(waypoint, point.curve_it));
+						canvas_interface->waypoint_remove(value_desc, waypoint);
+					}
+				}
+
 				times_to_move.insert(meta_data);
 				canvas_interface->waypoint_move(value_desc, time, deltatime);
 			}
 			point.time_point = TimePoint(new_time);
 		}
 		active_point.time_point = next_time;
+
+		for (auto it : waypoints_to_restore) {
+			Action::Handle 	action(Action::create("WaypointAdd"));
+
+			assert(action);
+			if(!action)
+				return;
+
+			action->set_param("canvas", canvas_interface->get_canvas());
+			action->set_param("canvas_interface", canvas_interface);
+			action->set_param("value_node", it.second->value_desc.get_value_node());
+//			action->set_param("time", i.first.get_time());
+			action->set_param("waypoint", it.first);
+
+			if(!canvas_interface->get_instance()->perform_action(action))
+				canvas_interface->get_ui_interface()->error(_("Action Failed."));
+		}
 	}
 
 	queue_draw();
@@ -778,6 +811,8 @@ void Widget_Curves::finish_dragging()
 	delete action_group_drag;
 	action_group_drag = nullptr;
 
+	saved_waypoints.clear();
+
 	pointer_state = POINTER_NONE;
 }
 
@@ -796,6 +831,8 @@ void Widget_Curves::cancel_dragging()
 		canvas_interface->get_instance()->clear_redo_stack();
 	}
 
+	saved_waypoints.clear();
+
 	pointer_state = POINTER_NONE;
 	queue_draw();
 }
diff --git a/synfig-studio/src/gui/widgets/widget_curves.h b/synfig-studio/src/gui/widgets/widget_curves.h
index b543f6b..4263639 100644
--- a/synfig-studio/src/gui/widgets/widget_curves.h
+++ b/synfig-studio/src/gui/widgets/widget_curves.h
@@ -108,6 +108,8 @@ private:
 	bool dragging_started_by_key;
 	synfigapp::Action::PassiveGrouper *action_group_drag;
 
+	std::vector<std::pair<synfig::Waypoint, std::list<CurveStruct>::iterator> > saved_waypoints;
+
 	static void set_value_base_for_channel_point(synfig::ValueBase &value_base, const ChannelPoint &channel_point, synfig::Real v);
 
 public: