Map loading
Last chapter we left off at creating some entities to test our rendering system, but now it's time to render a proper map. In this section we will create a text based map configuration which we will load.
Map config
First step, let's try to load a level based on a 2d map that looks like this.
N N W W W W W W
W W W . . . . W
W . . . B . . W
W . . . . . . W
W . P . . . . W
W . . . . . . W
W . . S . . . W
W . . . . . . W
W W W W W W W W
where:
. is an empty spot
W is a wall
P is the player
B is a box
S is a box spot
N is nothing: used for the outer edges of the map
Let's make a string for this, eventually we can load from a file but for simplicity let's go with a constant in the code for now.
#![allow(unused)] fn main() { pub fn initialize_level(world: &mut World) { const MAP: &str = " N N W W W W W W W W W . . . . W W . . . B . . W W . . . . . . W W . P . . . . W W . . . . . . W W . . S . . . W W . . . . . . W W W W W W W W W "; load_map(world, MAP.to_string()); } }
And here is the implementation of load map.
#![allow(unused)] fn main() { pub fn load_map(world: &mut World, map_string: String) { // read all lines let rows: Vec<&str> = map_string.trim().split('\n').map(|x| x.trim()).collect(); for (y, row) in rows.iter().enumerate() { let columns: Vec<&str> = row.split(' ').collect(); for (x, column) in columns.iter().enumerate() { // Create the position at which to create something on the map let position = Position { x: x as u8, y: y as u8, z: 0, // we will get the z from the factory functions }; // Figure out what object we should create match *column { "." => create_floor(world, position), "W" => { create_floor(world, position); create_wall(world, position); } "P" => { create_floor(world, position); create_player(world, position); } "B" => { create_floor(world, position); create_box(world, position); } "S" => { create_floor(world, position); create_box_spot(world, position); } "N" => (), c => panic!("unrecognized map item {}", c), } } } } }
The most interesting Rust concept here is probably the match. We are using the basic feature of pattern matching here, we are simply matching on the values of each token found in the map config, but we could do a lot of more advanced conditions or types of patterns.
MORE: Read more about pattern matching here.
Now let's run the game and see what our map looks like.
Final code below.
// Rust sokoban // main.rs use glam::Vec2; use ggez::{conf, event, Context, GameResult, graphics::{self, DrawParam, Image}}; use specs::{ join::Join, Builder, Component, ReadStorage, RunNow, System, VecStorage, World, WorldExt, }; use std::path; const TILE_WIDTH: f32 = 32.0; // Components #[derive(Debug, Component, Clone, Copy)] #[storage(VecStorage)] pub struct Position { x: u8, y: u8, z: u8, } #[derive(Component)] #[storage(VecStorage)] pub struct Renderable { path: String, } #[derive(Component)] #[storage(VecStorage)] pub struct Wall {} #[derive(Component)] #[storage(VecStorage)] pub struct Player {} #[derive(Component)] #[storage(VecStorage)] pub struct Box {} #[derive(Component)] #[storage(VecStorage)] pub struct BoxSpot {} // Systems pub struct RenderingSystem<'a> { context: &'a mut Context, } // System implementation impl<'a> System<'a> for RenderingSystem<'a> { // Data type SystemData = (ReadStorage<'a, Position>, ReadStorage<'a, Renderable>); fn run(&mut self, data: Self::SystemData) { let (positions, renderables) = data; // Clearing the screen (this gives us the backround colour) graphics::clear(self.context, graphics::Color::new(0.95, 0.95, 0.95, 1.0)); // Get all the renderables with their positions and sort by the position z // This will allow us to have entities layered visually. let mut rendering_data = (&positions, &renderables).join().collect::<Vec<_>>(); rendering_data.sort_by_key(|&k| k.0.z); // Iterate through all pairs of positions & renderables, load the image // and draw it at the specified position. for (position, renderable) in rendering_data.iter() { // Load the image let image = Image::new(self.context, renderable.path.clone()).expect("expected image"); let x = position.x as f32 * TILE_WIDTH; let y = position.y as f32 * TILE_WIDTH; // draw let draw_params = DrawParam::new().dest(Vec2::new(x, y)); graphics::draw(self.context, &image, draw_params).expect("expected render"); } // Finally, present the context, this will actually display everything // on the screen. graphics::present(self.context).expect("expected to present"); } } // This struct will hold all our game state // For now there is nothing to be held, but we'll add // things shortly. struct Game { world: World, } // This is the main event loop. ggez tells us to implement // two things: // - updating // - rendering impl event::EventHandler<ggez::GameError> for Game { fn update(&mut self, _context: &mut Context) -> GameResult { Ok(()) } fn draw(&mut self, context: &mut Context) -> GameResult { // Render game entities { let mut rs = RenderingSystem { context }; rs.run_now(&self.world); } Ok(()) } } // Register components with the world pub fn register_components(world: &mut World) { world.register::<Position>(); world.register::<Renderable>(); world.register::<Player>(); world.register::<Wall>(); world.register::<Box>(); world.register::<BoxSpot>(); } // Create a wall entity pub fn create_wall(world: &mut World, position: Position) { world .create_entity() .with(Position { z: 10, ..position }) .with(Renderable { path: "/images/wall.png".to_string(), }) .with(Wall {}) .build(); } pub fn create_floor(world: &mut World, position: Position) { world .create_entity() .with(Position { z: 5, ..position }) .with(Renderable { path: "/images/floor.png".to_string(), }) .build(); } pub fn create_box(world: &mut World, position: Position) { world .create_entity() .with(Position { z: 10, ..position }) .with(Renderable { path: "/images/box.png".to_string(), }) .with(Box {}) .build(); } pub fn create_box_spot(world: &mut World, position: Position) { world .create_entity() .with(Position { z: 9, ..position }) .with(Renderable { path: "/images/box_spot.png".to_string(), }) .with(BoxSpot {}) .build(); } pub fn create_player(world: &mut World, position: Position) { world .create_entity() .with(Position { z: 10, ..position }) .with(Renderable { path: "/images/player.png".to_string(), }) .with(Player {}) .build(); } // Initialize the level pub fn initialize_level(world: &mut World) { const MAP: &str = " N N W W W W W W W W W . . . . W W . . . B . . W W . . . . . . W W . P . . . . W W . . . . . . W W . . S . . . W W . . . . . . W W W W W W W W W "; load_map(world, MAP.to_string()); } pub fn load_map(world: &mut World, map_string: String) { // read all lines let rows: Vec<&str> = map_string.trim().split('\n').map(|x| x.trim()).collect(); for (y, row) in rows.iter().enumerate() { let columns: Vec<&str> = row.split(' ').collect(); for (x, column) in columns.iter().enumerate() { // Create the position at which to create something on the map let position = Position { x: x as u8, y: y as u8, z: 0, // we will get the z from the factory functions }; // Figure out what object we should create match *column { "." => create_floor(world, position), "W" => { create_floor(world, position); create_wall(world, position); } "P" => { create_floor(world, position); create_player(world, position); } "B" => { create_floor(world, position); create_box(world, position); } "S" => { create_floor(world, position); create_box_spot(world, position); } "N" => (), c => panic!("unrecognized map item {}", c), } } } } pub fn main() -> GameResult { let mut world = World::new(); register_components(&mut world); initialize_level(&mut world); // Create a game context and event loop let context_builder = ggez::ContextBuilder::new("rust_sokoban", "sokoban") .window_setup(conf::WindowSetup::default().title("Rust Sokoban!")) .window_mode(conf::WindowMode::default().dimensions(800.0, 600.0)) .add_resource_path(path::PathBuf::from("./resources")); let (context, event_loop) = context_builder.build()?; // Create the game state let game = Game { world }; // Run the main event loop event::run(context, event_loop, game) }
CODELINK: You can see the full code in this example here.