Add an API function for synchronously activating areas

doc/lua_api.txt

@@ -5266,6 +5266,12 @@ Environment access
     * Load the mapblocks containing the area from `pos1` to `pos2`.
       `pos2` defaults to `pos1` if not specified.
     * This function does not trigger map generation.
+* `minetest.activate_area(pos1, pos2)`
+    * Activate the mapblocks containing the area from `pos1` to `pos2`.
+    * The area will remain active at least until control passes from the Lua
+      code back to the Minetest engine.
+    * Mapblocks are not activated if they do not exist or are already active.
+    * This function does not trigger map generation.
 * `minetest.emerge_area(pos1, pos2, [callback], [param])`
     * Queue all blocks in the area from `pos1` to `pos2`, inclusive, to be
       asynchronously fetched from memory, loaded from disk, or if inexistent,

src/script/lua_api/l_env.cpp

@@ -1181,7 +1181,6 @@ int ModApiEnvMod::l_raycast(lua_State *L)
 int ModApiEnvMod::l_load_area(lua_State *L)
 {
 	GET_ENV_PTR;
-	MAP_LOCK_REQUIRED;
 
 	Map *map = &(env->getMap());
 	v3s16 bp1 = getNodeBlockPos(check_v3s16(L, 1));
@@ -1200,6 +1199,32 @@ int ModApiEnvMod::l_load_area(lua_State *L)
 	return 0;
 }
 
+// activate_area(p1, p2)
+// temporarily activate existing mapblocks in area p1..p2
+int ModApiEnvMod::l_activate_area(lua_State *L)
+{
+	GET_ENV_PTR;
+
+	Map &map = env->getMap();
+	v3s16 bpmin = getNodeBlockPos(check_v3s16(L, 1));
+	v3s16 bpmax = getNodeBlockPos(check_v3s16(L, 2));
+	sortBoxVerticies(bpmin, bpmax);
+	for (s16 z = bpmin.Z; z <= bpmax.Z; z++)
+	for (s16 y = bpmin.Y; y <= bpmax.Y; y++)
+	for (s16 x = bpmin.X; x <= bpmax.X; x++) {
+		v3s16 bp(x, y, z);
+		// blocks are skipped if they are already activated:
+		if (env->getBlockStatus(bp) < ServerEnvironment::BS_ACTIVE) {
+			MapBlock *block = map.emergeBlock(bp, false);
+			// blocks are skipped if they do not exist:
+			if (block)
+				env->activateBlock(block, 0);
+		}
+	}
+
+	return 0;
+}
+
 // emerge_area(p1, p2, [callback, context])
 // emerge mapblocks in area p1..p2, calls callback with context upon completion
 int ModApiEnvMod::l_emerge_area(lua_State *L)
@@ -1476,6 +1501,7 @@ void ModApiEnvMod::Initialize(lua_State *L, int top)
 	API_FCT(find_nodes_in_area_under_air);
 	API_FCT(fix_light);
 	API_FCT(load_area);
+	API_FCT(activate_area);
 	API_FCT(emerge_area);
 	API_FCT(delete_area);
 	API_FCT(get_perlin);

src/script/lua_api/l_env.h

@@ -149,6 +149,9 @@ class ModApiEnvMod : public ModApiBase {
 	// load_area(p1)
 	static int l_load_area(lua_State *L);
 
+	// activate_area(p1, p2)
+	static int l_activate_area(lua_State *L);
+
 	// emerge_area(p1, p2)
 	static int l_emerge_area(lua_State *L);