add wesnoth.terrain_mask lua function

`[terrain_mask]` had multiple unexpected behviours, see for example #3364
in parituclar `wesnoth.wml_actions.terrain_mask { x =2, y=2, mask="Ww"}`
will change the tile at (1,2) instead of (2,2), so instead of reusing
the old terrain mask code i wrote a new function that behaves as one
would expect. `wesnoth.terrain_mask` does not have a `border=` parameter
but a `is_odd` parameter that specifies that a map is in the odd format
 __    __
/00\__/20\__
\__/10\__/30\
/01\__/21\__/
\__/11\__/31\
/02\__/22\__/
\__/  \__/

instead of the even map format
    __    __
 __/10\__/30\
/00\__/20\__/
\__/11\__/31\
/01\__/21\__/
\__/12\__/32\
   \__/  \__/

(Monospaced font required to see ascii images.)

The lua function also has a lua interfacte, meaning it does not take wml
tables but normal lua tables making it easier to use from lua code.

(cherry-picked from commit a3367ee)

src/game_board.cpp

@@ -283,10 +283,8 @@ boost::optional<std::string> game_board::replace_map(const gamemap & newmap) {
 	return ret;
 }
 
-
-
 void game_board::overlay_map(const gamemap & mask_map, const config & cfg, map_location loc) {
-	map_->overlay(mask_map, cfg, loc);
+	map_->overlay_old(mask_map, cfg, loc);
 }
 
 bool game_board::change_terrain(const map_location &loc, const std::string &t_str,

src/game_board.hpp

@@ -156,7 +156,7 @@ class game_board : public display_context
 
 	bool try_add_unit_to_recall_list(const map_location& loc, const unit_ptr u);
 	boost::optional<std::string> replace_map (const gamemap & r);
-	void overlay_map (const gamemap & o, const config & cfg, map_location loc);
+	void overlay_map(const gamemap & o, const config & cfg, map_location loc);
 
 	bool change_terrain(const map_location &loc, const std::string &t,
 	                    const std::string & mode, bool replace_if_failed); //used only by lua

src/map/map.cpp

@@ -206,30 +206,8 @@ std::string gamemap::write() const
 {
 	return t_translation::write_game_map(tiles_, starting_positions_, t_translation::coordinate{ border_size(), border_size() }) + "\n";
 }
-namespace
-{
-	struct overlay_rule
-	{
-		t_translation::ter_list old_;
-		t_translation::ter_list new_;
-		terrain_type_data::merge_mode mode_;
-		boost::optional<t_translation::terrain_code> terrain_;
-		bool use_old_;
-		bool replace_if_failed_;
-
-		overlay_rule()
-			: old_()
-			, new_()
-			, mode_(terrain_type_data::BOTH)
-			, terrain_()
-			, use_old_(false)
-			, replace_if_failed_(false)
-		{
 
-		}
-	};
-}
-void gamemap::overlay(const gamemap& m, const config& rules_cfg, map_location loc)
+void gamemap::overlay_old(const gamemap& m, const config& rules_cfg, map_location loc)
 {
 	int xpos = loc.x;
 	int ypos = loc.y;
@@ -297,6 +275,89 @@ void gamemap::overlay(const gamemap& m, const config& rules_cfg, map_location lo
 	}
 }
 
+void gamemap::overlay(const gamemap& m, map_location loc, const std::vector<overlay_rule>& rules, bool m_is_odd, bool ignore_special_locations)
+{
+	int xpos = loc.wml_x();
+	int ypos = loc.wml_y();
+
+	const int xstart = std::max<int>(0, -xpos);
+	const int xend = std::min<int>(m.total_width(), total_width() -xpos);
+	const int xoffset = xpos;
+
+	const int ystart_even = std::max<int>(0, -ypos);
+	const int yend_even = std::min<int>(m.total_height(), total_height() - ypos);
+	const int yoffset_even = ypos;
+
+	const int ystart_odd = std::max<int>(0, -ypos +(xpos & 1) -(m_is_odd ? 1 : 0));
+	const int yend_odd = std::min<int>(m.total_height(), total_height() - ypos +(xpos & 1) -(m_is_odd ? 1 : 0));
+	const int yoffset_odd = ypos -(xpos & 1) + (m_is_odd ? 1 : 0);
+
+	for(int x1 = xstart; x1 != xend; ++x1) {
+		int ystart, yend, yoffset;
+		if(x1 & 1) {
+			ystart = ystart_odd , yend = yend_odd , yoffset = yoffset_odd;
+		}
+		else {
+			ystart = ystart_even, yend = yend_even, yoffset = yoffset_even;
+		}
+		for(int y1 = ystart; y1 != yend; ++y1) {
+			const int x2 = x1 + xoffset;
+			const int y2 = y1 + yoffset;//ypos + ((xpos & 1) && (x1 & 1) ? 1 : 0);
+
+			const t_translation::terrain_code t = m.tiles_.get(x1,y1);
+			const t_translation::terrain_code current = tiles_.get(x2, y2);
+
+			if(t == t_translation::FOGGED || t == t_translation::VOID_TERRAIN) {
+				continue;
+			}
+
+			// See if there is a matching rule
+			const overlay_rule* rule = nullptr;
+			for(const overlay_rule& current_rule : rules)
+			{
+				if(!current_rule.old_.empty() && !t_translation::terrain_matches(current, current_rule.old_)) {
+					continue;
+				}
+				if(!current_rule.new_.empty() && !t_translation::terrain_matches(t, current_rule.new_)) {
+					continue;
+				}
+				rule = &current_rule;
+				break;
+			}
+
+			if (!rule) {
+				set_terrain(map_location(x2, y2, wml_loc()), t);
+			}
+			else if(!rule->use_old_) {
+				set_terrain(map_location(x2, y2, wml_loc()), rule->terrain_ ? *rule->terrain_ : t , rule->mode_, rule->replace_if_failed_);
+			}
+		}
+	}
+
+	if (!ignore_special_locations) {
+		for(auto& pair : m.starting_positions_.left) {
+
+			int x = pair.second.wml_x();
+			int y = pair.second.wml_y();
+			if(x & 1) {
+				if(x < xstart || x >= xend || y < ystart_odd || y >= yend_odd) {
+					continue;
+				}
+			}
+			else {
+				if(x < xstart || x >= xend || y < ystart_even || y >= yend_even) {
+					continue;
+				}
+			}
+			int x_new = x + xoffset;
+			int y_new = y + ((x & 1 ) ? yoffset_odd : yoffset_even);
+			map_location pos_new = map_location(x_new, y_new, wml_loc());
+
+			starting_positions_.left.erase(pair.first);
+			starting_positions_.insert(starting_positions::value_type(pair.first, t_translation::coordinate(pos_new.x, pos_new.y)));
+		}
+	}
+}
 t_translation::terrain_code gamemap::get_terrain(const map_location& loc) const
 {
 

src/map/map.hpp

@@ -22,6 +22,8 @@ class config;
 #include "terrain/translation.hpp"
 #include "terrain/type_data.hpp"
 
+#include <boost/optional.hpp>
+
 //class terrain_type_data; Can't forward declare because of enum
 
 /**
@@ -83,8 +85,30 @@ class gamemap
 
 	std::string write() const;
 
+	struct overlay_rule
+	{
+		t_translation::ter_list old_;
+		t_translation::ter_list new_;
+		terrain_type_data::merge_mode mode_;
+		boost::optional<t_translation::terrain_code> terrain_;
+		bool use_old_;
+		bool replace_if_failed_;
+
+		overlay_rule()
+			: old_()
+			, new_()
+			, mode_(terrain_type_data::BOTH)
+			, terrain_()
+			, use_old_(false)
+			, replace_if_failed_(false)
+		{
+
+		}
+	};
+
 	/** Overlays another map onto this one at the given position. */
-	void overlay(const gamemap& m, const config& rules, map_location loc);
+	void overlay_old(const gamemap& m, const config& rules, map_location loc);
+	void overlay(const gamemap& m, map_location loc, const std::vector<overlay_rule>& rules, bool is_odd, bool ignore_special_locations);
 
 	/** Effective map width. */
 	int w() const { return w_; }

src/scripting/game_lua_kernel.cpp

@@ -1012,6 +1012,115 @@ int game_lua_kernel::intf_set_terrain(lua_State *L)
 	return 0;
 }
 
+static bool luaW_tableget(lua_State *L, int index, const char* key)
+{
+	lua_pushstring(L, key);
+	lua_gettable(L, index);
+	if(lua_isnil(L, -1)) {
+		lua_pop(L, 1);
+		return false;
+	}
+	return true;
+}
+
+static utils::string_view luaW_tostring(lua_State *L, int index)
+{
+	size_t len = 0;
+	const char* str = lua_tolstring (L, index, &len);
+	return utils::string_view(str, len);
+}
+
+/**
+ * Reaplces part of rhe map.
+ * - Arg 1: map location.
+ * - Arg 2: map data string.
+ * - Arg 3: table for optional named arguments
+ *   - is_odd: boolen, if Arg2 has the odd mapo format (as if it was cut from a odd map location)
+ *   - ignore_special_locations: boolean
+ *   - rules: table of tables
+*/
+int game_lua_kernel::intf_terrain_mask(lua_State *L)
+{
+	map_location loc = luaW_checklocation(L, 1);
+	std::string t_str(luaL_checkstring(L, 2));
+	bool is_odd = false;
+	bool ignore_special_locations = false;
+	std::vector<gamemap::overlay_rule> rules;
+
+	if(lua_istable(L, 3)) {
+		if(luaW_tableget(L, 3, "is_odd")) {
+			is_odd = luaW_toboolean(L, -1);
+			lua_pop(L, 1);
+		}
+		if(luaW_tableget(L, 3, "ignore_special_locations")) {
+			ignore_special_locations = luaW_toboolean(L, -1);
+			lua_pop(L, 1);
+		}
+		if(luaW_tableget(L, 3, "rules")) {
+			if(!lua_istable(L, -1)) {
+				return luaL_argerror(L, 3, "rules must be a table");
+			}
+
+			for (int i = 1, i_end = lua_rawlen(L, -1); i <= i_end; ++i)
+			{
+				lua_rawgeti(L, -1, i);
+				if(!lua_istable(L, -1)) {
+					return luaL_argerror(L, 3, "rules must be a table of tables");
+				}
+				rules.push_back(gamemap::overlay_rule());
+				auto& rule = rules.back();
+				if(luaW_tableget(L, -1, "old")) {
+					rule.old_ = t_translation::read_list(luaW_tostring(L, -1));
+					lua_pop(L, 1);
+				}
+
+				if(luaW_tableget(L, -1, "new")) {
+					rule.new_ = t_translation::read_list(luaW_tostring(L, -1));
+					lua_pop(L, 1);
+				}
+
+				if(luaW_tableget(L, -1, "mode")) {
+					auto str = luaW_tostring(L, -1);
+					rule.mode_ = str == "base" ? terrain_type_data::BASE : (str == "overlay" ? terrain_type_data::OVERLAY : terrain_type_data::BOTH);
+					lua_pop(L, 1);
+				}
+
+				if(luaW_tableget(L, -1, "terrain")) {
+					const t_translation::ter_list terrain = t_translation::read_list(luaW_tostring(L, -1));
+					if(!terrain.empty()) {
+						rule.terrain_ = terrain[0];
+					}
+					lua_pop(L, 1);
+				}
+
+				if(luaW_tableget(L, -1, "use_old")) {
+					rule.use_old_ = luaW_toboolean(L, -1);
+					lua_pop(L, 1);
+				}
+
+				if(luaW_tableget(L, -1, "replace_if_failed")) {
+					rule.replace_if_failed_ = luaW_toboolean(L, -1);
+					lua_pop(L, 1);
+				}
+
+				lua_pop(L, 1);
+			}
+			lua_pop(L, 1);
+		}
+	}
+
+
+	gamemap mask_map(resources::gameboard->map().tdata(), "");
+	mask_map.read(t_str, false);
+	board().map_->overlay(mask_map, loc, rules, is_odd, ignore_special_locations);
+
+	if (game_display_) {
+		game_display_->needs_rebuild(true);
+	}
+
+	return 0;
+}
+
 /**
  * Gets details about a terrain.
  * - Arg 1: terrain code string.
@@ -4156,6 +4265,7 @@ game_lua_kernel::game_lua_kernel(game_state & gs, play_controller & pc, reports
 		{ "switch_ai",                 &intf_switch_ai                                                      },
 		{ "synchronize_choice",        &intf_synchronize_choice                                             },
 		{ "synchronize_choices",       &intf_synchronize_choices                                            },
+		{ "terrain_mask",              &dispatch<&game_lua_kernel::intf_terrain_mask               >        },
 		{ "zoom",                      &dispatch<&game_lua_kernel::intf_zoom                       >        },
 		{ "teleport",                  &dispatch<&game_lua_kernel::intf_teleport                   >        },
 		{ "unit_ability",              &dispatch<&game_lua_kernel::intf_unit_ability               >        },

src/scripting/game_lua_kernel.hpp

@@ -91,6 +91,7 @@ class game_lua_kernel : public lua_kernel_base
 	int intf_lock_view(lua_State *L);
 	int intf_get_terrain(lua_State *L);
 	int intf_set_terrain(lua_State *L);
+	int intf_terrain_mask(lua_State *L);
 	int intf_get_terrain_info(lua_State *L);
 	int intf_get_time_of_day(lua_State *L);
 	int intf_get_village_owner(lua_State *L);