add [replace_map] functionality.

Allows completely changing the map in a scenario, including loading a
map with a different size.

changelog

@@ -47,6 +47,8 @@ Version 1.5.7+svn:
    * the animate_unit action can now animate multiple units
    * the animate_unit action can now change the direction the unit is facing
      with a SLF
+   * add a [replace_map] map="file" event that can load a map of a different
+     size in a scenario
  * Miscellaneous and bug fixes:
    * Added the sunset feature to the new dialogs.
    * Fix the calculate feature in the test scenario.

data/scenario-test.cfg

@@ -1135,6 +1135,44 @@ Result:
         [/end_turn]
     [/event]
 
+    [label]
+        x,y=10,2
+        text="map change"
+    [/label]
+	
+    [event]
+        name=moveto
+        [filter]
+            x,y=10,2
+        [/filter]
+        [message]
+            side=2
+            message="Suddenly, Elves Besieged!"
+        [/message]
+		[replace_map]
+			map="{campaigns/Heir_To_The_Throne/maps/01_The_Elves_Besieged.map}"
+		[/replace_map]		
+    [/event]
+
+    [label]
+        x,y=10,3
+        text="map change2"
+    [/label]
+	
+    [event]
+        name=moveto
+        [filter]
+            x,y=10,3
+        [/filter]
+        [message]
+            side=2
+            message="Suddenly, Blackwater Port!"
+        [/message]
+		[replace_map]
+			map="{campaigns/Heir_To_The_Throne/maps/02_Blackwater_Port.map}"
+		[/replace_map]	
+    [/event]
+
     # Capture connected villages near 13,2 for team 2
     [event]
         name=prestart

src/game_events.cpp

@@ -3105,6 +3105,23 @@ namespace {
         }
 	}
 
+	// Experimental map replace
+	WML_HANDLER_FUNCTION(replace_map,handler,/*event_info*/,cfg)
+	{
+		gamemap map(*game_map);
+		try {
+			map.read(cfg["map"]);
+		} catch(incorrect_map_format_exception&) {
+			ERR_NG << "terrain mask is in the incorrect format, and couldn't be applied\n";
+			return;
+		} catch(twml_exception& e) {
+			e.show(*screen);
+			return;
+		}
+		*game_map = map;
+        screen->reload_map();
+		handler.rebuild_screen() = true;
+	}
 
 	/** Handles all the different types of actions that can be triggered by an event. */