Removed resources::units once again

I had re-added it in a limited context in eaea9be117 since I needed it to fix
(IIRC) a crash in the editor when adding units, since the editor didn't have a game_board.
However, looking at the code again, I realized that the display class (base of editor_display)
holds a pointer to a display_context object. map_context inherits from display_context, and
the editor sets the editor_display's display_context to the current map_context. Therefor, I
could just access the units needed via display::get_units, instead of needing a global pointer.

src/editor/controller/editor_controller.cpp

@@ -159,7 +159,6 @@ void editor_controller::init_music(const config& game_config)
 
 editor_controller::~editor_controller()
 {
-	resources::units = nullptr;
 	resources::tod_manager = nullptr;
 	resources::filter_con = nullptr;
 

src/editor/map/context_manager.cpp

@@ -87,7 +87,6 @@ public:
 
 		// TODO register the tod_manager with the gui?
 		resources::tod_manager = context_manager_.get_map_context().get_time_manager();
-		resources::units = &context_manager_.get_map_context().units();
 		resources::filter_con = &context_manager_.gui();
 
 		context_manager_.gui().replace_overlay_map(&context_manager_.get_map_context().get_overlays());

src/play_controller.cpp

@@ -125,7 +125,6 @@ static void clear_resources()
 	resources::tunnels = nullptr;
 	resources::undo_stack = nullptr;
 	resources::recorder = nullptr;
-	resources::units = nullptr;
 	resources::whiteboard.reset();
 	resources::classification = nullptr;
 }
@@ -212,7 +211,6 @@ void play_controller::init(const config& level)
 		resources::gameboard = &gamestate().board_;
 		resources::gamedata = &gamestate().gamedata_;
 		resources::tod_manager = &gamestate().tod_manager_;
-		resources::units = &gamestate().board_.units_;
 		resources::filter_con = &gamestate();
 		resources::undo_stack = &undo_stack();
 		resources::game_events = gamestate().events_manager_.get();
@@ -295,7 +293,6 @@ void play_controller::reset_gamestate(const config& level, int replay_pos)
 	resources::gameboard = nullptr;
 	resources::gamedata = nullptr;
 	resources::tod_manager = nullptr;
-	resources::units = nullptr;
 	resources::filter_con = nullptr;
 	resources::lua_kernel = nullptr;
 	resources::game_events = nullptr;
@@ -312,7 +309,6 @@ void play_controller::reset_gamestate(const config& level, int replay_pos)
 	resources::gameboard = &gamestate().board_;
 	resources::gamedata = &gamestate().gamedata_;
 	resources::tod_manager = &gamestate().tod_manager_;
-	resources::units = &gamestate().board_.units_;
 	resources::filter_con = &gamestate();
 	resources::undo_stack = &undo_stack();
 	resources::game_events = gamestate().events_manager_.get();

src/resources.cpp

@@ -30,7 +30,6 @@ namespace resources
 	fake_unit_manager    *fake_units = nullptr;
 	pathfind::manager    *tunnels = nullptr;
 	actions::undo_list   *undo_stack = nullptr;
-	unit_map             *units = nullptr;
 	std::shared_ptr<wb::manager> whiteboard = std::shared_ptr<wb::manager>();
 	game_classification  *classification = nullptr;
 	bool                 simulation_ = false;

src/resources.hpp

@@ -57,7 +57,6 @@ namespace resources
 	extern ::tod_manager          *tod_manager;
 	extern pathfind::manager      *tunnels;
 	extern actions::undo_list     *undo_stack;
-	extern unit_map               *units;
 	extern std::shared_ptr<wb::manager> whiteboard;
 	extern bool                   simulation_;
 }

src/units/abilities.cpp

@@ -17,6 +17,7 @@
  *  Manage unit-abilities, like heal, cure, and weapon_specials.
  */
 
+#include "display.hpp"
 #include "display_context.hpp"
 #include "game_board.hpp"
 #include "lexical_cast.hpp"
@@ -145,8 +146,8 @@ bool unit::get_ability_bool(const std::string& tag_name, const map_location& loc
 		}
 	}
 
-	assert(resources::units);
-	const unit_map& units = *resources::units;
+	assert(display::get_singleton());
+	const unit_map& units = display::get_singleton()->get_units();
 
 	map_location adjacent[6];
 	get_adjacent_tiles(loc,adjacent);
@@ -186,8 +187,8 @@ unit_ability_list unit::get_abilities(const std::string& tag_name, const map_loc
 		}
 	}
 
-	assert(resources::units);
-	const unit_map& units = *resources::units;
+	assert(display::get_singleton());
+	const unit_map& units = display::get_singleton()->get_units();
 
 	map_location adjacent[6];
 	get_adjacent_tiles(loc,adjacent);
@@ -312,8 +313,8 @@ bool unit::ability_active(const std::string& ability,const config& cfg,const map
 	map_location adjacent[6];
 	get_adjacent_tiles(loc,adjacent);
 
-	assert(resources::units);
-	const unit_map& units = *resources::units;
+	assert(display::get_singleton());
+	const unit_map& units = display::get_singleton()->get_units();
 
 	for (const config &i : cfg.child_range("filter_adjacent"))
 	{
@@ -449,15 +450,17 @@ T get_single_ability_value(const config::attribute_value& v, T def, const map_lo
 	return v.apply_visitor(make_get_ability_value_visitor(def, [&](const std::string& s) {
 
 			try {
-				assert(resources::units);
-				auto u_itor = resources::units->find(sender_loc);
+				assert(display::get_singleton());
+				const unit_map& units = display::get_singleton()->get_units();
 
-				if(u_itor == resources::units->end()) {
+				auto u_itor = units.find(sender_loc);
+
+				if(u_itor == units.end()) {
 					return def;
 				}
 				wfl::map_formula_callable callable(std::make_shared<wfl::unit_callable>(*u_itor));
-				u_itor = resources::units->find(receiver_loc);
-				if(u_itor != resources::units->end()) {
+				u_itor = units.find(receiver_loc);
+				if(u_itor != units.end()) {
 					callable.add("other", wfl::variant(std::make_shared<wfl::unit_callable>(*u_itor)));
 				}
 				return formula_handler(wfl::formula(s, new wfl::gamestate_function_symbol_table), callable);
@@ -913,8 +916,8 @@ bool attack_type::special_active(const config& special, AFFECTS whom,
 	}
 
 	// Get the units involved.
-	assert(resources::units);
-	const unit_map& units = *resources::units;
+	assert(display::get_singleton());
+	const unit_map& units = display::get_singleton()->get_units();
 
 	unit_map::const_iterator self  = units.find(self_loc_);
 	unit_map::const_iterator other = units.find(other_loc_);