Safely import towns of different size. fix #760

rsrc/dialogs/select-import-town.xml

@@ -9,13 +9,11 @@
 	<text size='large' top='6' left='50' width='175' height='17'>Importing a town</text>
 	<text name='prompt' top='143' left='50' width='162' height='27'>What town do you wish to import? (0 - {{max-num}})</text>
 	<text top='27' left='50' width='301' height='54'>
-		Enter a town number and hit OK, and you will be asked to select a scenario file.
-		The town with that number in the selected scenario will then be loaded in over the current town.
+		The town with this number in the selected scenario be imported.
 	</text>
 	<button name='cancel' type='regular' top='181' left='212'>Cancel</button>
 	<text top='83' left='50' width='301' height='54'>
-		Warning: This will write over the town currently in memory.
-		Also, the town you select must be the same size (large/medium/small) as the town currently in memory.
+		Warning: This will overwrite over the town currently in memory.
 	</text>
 	<button name='choose' type='regular' top='146' left='281'>Choose</button>
 </dialog>

src/scenedit/scen.main.cpp

@@ -97,6 +97,8 @@ rectangle search_field_rect;
 
 extern void set_up_apple_events();
 
+extern void clamp_view_center(cTown* town);
+
 // TODO: these should be members of some global entity instead of being here
 std::unordered_map<std::string, std::shared_ptr <iEventListener>> event_listeners;
 cDrawableManager drawable_mgr;
@@ -654,6 +656,7 @@ void handle_menu_choice(eMenu item_hit) {
 				scenario.towns[cur_town] = town;
 				::town = town;
 				change_made = true;
+				clamp_view_center(town);
 				redraw_screen();
 			}
 			break;

src/scenedit/scen.townout.cpp

@@ -1896,3 +1896,9 @@ cOutdoors* pick_import_out() {
 	temp_scenario.outdoors[sector.x][sector.y] = nullptr;
 	return out;
 }
+
+// after importing a town, the view center might be out-of-bounds
+void clamp_view_center(cTown* town) {
+	cen_x = min(cen_x, town->max_dim - 5);
+	cen_y = min(cen_y, town->max_dim - 5);
+}

src/scenedit/scen.undo.cpp

@@ -20,6 +20,7 @@ extern eScenMode overall_mode;
 extern eDrawMode draw_mode;
 extern void apply_outdoor_shift(rectangle mod);
 extern void clamp_current_section();
+extern void clamp_view_center(cTown* town);
 
 cTerrainAction::cTerrainAction(std::string name, short town_num, location where, bool reversed) : cAction(name, reversed) {
 	area.is_town = true;
@@ -556,12 +557,16 @@ aImportTown::~aImportTown() {
 
 bool aImportTown::undo_me() {
 	scenario.towns[which] = old_town;
+	clamp_view_center(old_town);
 	set_current_town(which);
+	start_town_edit();
 	return true;
 }
 
 bool aImportTown::redo_me() {
 	scenario.towns[which] = new_town;
+	clamp_view_center(new_town);
 	set_current_town(which);
+	start_town_edit();
 	return true;
 }