feat(editor): the vertical profile shows the terrain model, the terrain follows it, the camera follows the plot

- The plot draws the ground of the terrain model (NMT) as measured, before any earthworks. The squares under the route are fetched in the background. The tooltip gives the grade line's distance from the model.
- Applying a profile lays the formation of the changed tracks anew, or reshapes the route's earthworks when there are any, so the heightmap terrain follows the new grade line. The terrain step is joined to the track step: one undo takes both back.
- In 3D and in the top view, the camera shows the part of the route the plot shows once the plot stops moving. It keeps clear of the floating plot window. A toggle turns this off.
- nmt_shape_tracks can shape only the given tracks, removing the modifiers of their paths that are gone.

application/editormode.h

@@ -402,7 +402,9 @@ class editor_mode : public application_mode, private editor_track::observer
 	// Rebuild: the chunks there already are made anew too, and the formation laid before is forgotten, as when the tracks moved
 	void nmt_make(std::vector<heightmap::chunk_key> const &Keys, bool const Rebuild = false);
 	bool add_chunk_from_nmt(heightmap::chunk_key const &Key);
-	void nmt_shape_tracks();
+	// Only: the paths of these tracks are shaped anew, the modifiers of those removed taken away; null: all of them. the number
+	// of the modifiers laid
+	std::size_t nmt_shape_tracks(std::vector<TTrack *> const *Only = nullptr);
 	void nmt_update();
 	void render_nmt_ui();
 	// a scenery begun from nothing, with no tracks nor terrain, is asked as the first track is laid whether it wants the terrain
@@ -2275,6 +2277,9 @@ class editor_mode : public application_mode, private editor_track::observer
 		std::vector<editor_track::route_sample> samples;
 		std::vector<TTrack *> created; // the paths the last apply split off the route
 		std::vector<double> terrain; // NaN where there's no terrain
+		std::vector<double> model; // the ground of the terrain model (NMT) as measured; NaN where it's not known
+		bool model_waiting{false}; // squares of the model under the route still to come
+		double model_polled{0.0};
 		// what the joined ends take their height and grade from, when it's a switch: shown on the plot
 		std::string start_inherits, end_inherits;
 		// depth of the formation under the grade line, the rail top, of the track of each sample: the formation, not the rails,
@@ -2306,7 +2311,13 @@ class editor_mode : public application_mode, private editor_track::observer
 		double view_centre{0.0};
 		float exaggeration{20.0f};
 		bool show_terrain{true};
+		bool show_model{true};
 		bool show_track{true};
+		bool camera_follows{true};
+		// the part of the route the plot shows: as last seen and when, and as the camera last showed it
+		std::pair<double, double> view_seen{0.0, 0.0};
+		double view_seen_time{0.0};
+		std::pair<double, double> view_framed{0.0, 0.0};
 		bool show_plan{true};
 		int selected{-1};
 		int dragging{-1};
@@ -2368,6 +2379,8 @@ class editor_mode : public application_mode, private editor_track::observer
 	void profile_open_selection(std::vector<TTrack *> const &Tracks);
 	void profile_follow_selection();
 	void profile_resample();
+	// the ground of the terrain model under the route, as it was measured before any earthworks
+	void profile_sample_model();
 	void profile_recognize();
 	void profile_fit_ground();
 	// depth of the foot of the ballast under the rail top, and its distance from the axis
@@ -2379,8 +2392,14 @@ class editor_mode : public application_mode, private editor_track::observer
 	void profile_restore_ground();
 	void render_profile_earthworks();
 	void profile_check();
-	void profile_apply();
+	// Terrain: the heightmap terrain follows the tracks changed
+	void profile_apply(bool const Terrain = false);
+	// the terrain under the tracks changed by the last Edits steps of the history which changed tracks
+	void profile_follow_terrain(std::size_t const Edits);
 	void profile_fit_view();
+	// the camera shows the part of the route the plot shows, once the plot stops moving
+	void profile_follow_view();
+	void profile_frame_view();
 	void profile_after_undo();
 	void profile_follow_edits();
 	struct profile_view;