fix(editor): Esc takes back what a drag did

Esc in the middle of dragging a point of a track kept the moved point,
and the hint said so; dragging a straight was taken back but left an
empty step in the history; a vertex or the radius grip of a curve stayed
moved in the design. Now Esc puts back what was there before the drag in
all three, and the history doesn't keep a step for it.

application/editormode.cpp

@@ -973,6 +973,16 @@ void editor_mode::undo_last()
     }
 }
 
+void editor_mode::drop_step(std::size_t const Step)
+{
+    if (Step == 0 || m_history.size() != Step)
+        return;
+    auto const redo{g_redo.size()};
+    undo_one();
+    if (g_redo.size() > redo)
+        g_redo.erase(g_redo.begin() + redo, g_redo.end());
+}
+
 void editor_mode::undo_one()
 {
     if (m_history.empty())

application/editormode.h

@@ -174,6 +174,7 @@ class editor_mode : public application_mode, private editor_track::observer, pri
 	void redo_last();
 	// a single step of the history, see undo_last()
 	void undo_one();
+	void drop_step(std::size_t const Step);
 	void redo_one();
 	// the changes of the heightmap terrain since the last step become a step of the history: a stroke of the brush,
 	// or what a frame did; the next change is recorded from now on
@@ -984,6 +985,7 @@ class editor_mode : public application_mode, private editor_track::observer, pri
 		bool fit_has_before{false};
 		bool fit_has_after{false};
 		std::vector<std::pair<TTrack *, editor_track::state>> drag_states;
+		std::size_t drag_step{0};
 		glm::dvec3 preview_start{0.0};
 		glm::dvec3 preview_end{0.0};
 		glm::dvec3 edit_start{0.0};
@@ -1551,6 +1553,7 @@ class editor_mode : public application_mode, private editor_track::observer, pri
 		bool moved{false};
 		glm::vec2 from{0.f};
 		double height{0.0};
+		std::size_t step{0};
 	};
 	point_drag m_point_drag;
 	struct handle_drag
@@ -2258,6 +2261,7 @@ class editor_mode : public application_mode, private editor_track::observer, pri
 	void draw_infra_overlay() const;
 
 	bool m_route_dragging{false};
+	alignment::design m_route_drag_from;
 	float m_track_snap_radius{1.0f};
 	bool m_track_align_tangent{true};
 	bool m_track_drag_connected{true};

application/editormodelay.cpp

@@ -351,6 +351,7 @@ void editor_mode::point_drag_update()
 		for (auto *dragged : m_track_drag)
 			states.emplace_back(dragged, editor_track::capture(*dragged));
 		push_track_snapshot(std::move(states));
+		drag.step = m_history.size();
 		records_watch_begin();
 	}
 	screen_projection const projection;

application/editormoderoute.cpp

@@ -1102,6 +1102,8 @@ void editor_mode::render_route_gizmo()
 		}
 		return;
 	}
+	if (false == m_route_dragging)
+		m_route_drag_from = route.design;
 	m_route_dragging = true;
 	if (grip)
 	{

application/editormodestraights.cpp

@@ -638,6 +638,7 @@ void editor_mode::render_straight_gizmo()
 			if (false == state.fitting)
 			{
 				push_track_snapshot(state.drag_states);
+				state.drag_step = m_history.size();
 				m_track_drag = tracks;
 			}
 		}
@@ -731,6 +732,7 @@ void editor_mode::cancel_track_tools()
 			m_track_dirty = true;
 			commit_track_drag(true);
 			m_track_drag.clear();
+			drop_step(state.drag_step);
 		}
 		state.dragging = false;
 		state.fitting = false;
@@ -743,10 +745,22 @@ void editor_mode::cancel_track_tools()
 	m_signal.placing = false;
 	m_signal.moving = false;
 	m_handle_drag = {};
+	if (m_route_dragging)
+	{
+		m_route_dragging = false;
+		m_route.design = m_route_drag_from;
+		route_update();
+	}
 	if (m_point_drag.active)
 	{
+		auto const step{m_point_drag.moved ? m_point_drag.step : 0};
 		m_track_snap = {};
-		point_drag_finish();
+		m_record_watch = {};
+		m_point_drag = {};
+		m_track_drag.clear();
+		m_track_drag_points.clear();
+		m_track_joints.clear();
+		drop_step(step);
 	}
 	if (m_switch.placing)
 	{

application/editormodetrack.cpp

@@ -1695,7 +1695,7 @@ std::vector<editor_mode::key_hint> editor_mode::track_key_hints(bool const All)
 		gizmo = true;
 	}
 	else if (m_point_drag.moved)
-		hints = {{"Drag", "moves the point, level"}, {"Over a free end", "the end joins it"}, {"Release", "done"}, {"Esc", "done"}};
+		hints = {{"Drag", "moves the point, level"}, {"Over a free end", "the end joins it"}, {"Release", "done"}, {"Esc", "cancel"}};
 	else if (m_track_point.valid())
 	{
 		char const *action{"moves the point along the axes"};