set up visibility system

src/main.rs

@@ -7,6 +7,8 @@ mod map;
 pub use map::*;
 mod components;
 pub use components::*;
+mod visibility_system;
+pub use visibility_system::VisibilitySystem;
 
 #[macro_use]
 extern crate specs_derive;
@@ -23,7 +25,7 @@ fn try_move_player(delta_x: i32, delta_y: i32, ecs: &mut World) {
     for (_player, pos) in (&mut players, &mut positions).join() {
         let x = min(79, max(0, pos.x + delta_x));
         let y = min(49, max(0, pos.y + delta_y));
-        if map.tile_at(x,y) != TileType::Wall {
+        if map.tile_at(x, y) != TileType::Wall {
             pos.x = x;
             pos.y = y;
         }
@@ -69,8 +71,8 @@ impl<'a> System<'a> for LeftWalker {
 
 impl State {
     fn run_systems(&mut self) {
-        let mut lw = LeftWalker {};
-        lw.run_now(&self.ecs);
+        let mut vis = VisibilitySystem {};
+        vis.run_now(&self.ecs);
         self.ecs.maintain();
     }
 }
@@ -104,6 +106,7 @@ fn main() {
     gs.ecs.register::<Renderable>();
     gs.ecs.register::<LeftMover>();
     gs.ecs.register::<Player>();
+    gs.ecs.register::<Viewshed>();
 
     gs.ecs
         .create_entity()
@@ -117,6 +120,10 @@ fn main() {
             bg: RGB::named(rltk::BLACK),
         })
         .with(Player {})
+        .with(Viewshed {
+            visible_tiles: Vec::new(),
+            range: 8,
+        })
         .build();
 
     for i in 0..10 {