feat: Barely working tilemap system

- Added tilemap bundle
- Added HALVED_METERS_PER_PIXEL constant

src/layout/tilemap.rs

@@ -0,0 +1,60 @@
+use bevy::{
+    image::{
+        ImageArrayLayout,
+        ImageLoaderSettings,
+    },
+    prelude::*,
+    sprite_render::{
+        TileData,
+        TilemapChunk,
+        TilemapChunkTileData,
+    },
+};
+use bevy_rapier2d::prelude::*;
+
+use crate::{HALVED_PIXELS_PER_METER, PIXELS_PER_METER};
+
+const TILEMAP_PATH: &'static str = "sprites/level/tilemap.png";
+const TILE_DISPLAY_SIZE: UVec2 = UVec2::splat(PIXELS_PER_METER as u32);
+
+#[derive(Component, Debug, PartialEq, Eq, Default, Clone, Copy, Reflect)]
+#[reflect(Component, Debug, PartialEq, Default, Clone)]
+pub struct Tilemap;
+
+pub fn tilemap_bundle(
+    asset_server: &Res<AssetServer>,
+    size: UVec2,
+    tiles: Vec<(u16, UVec2)>,
+    colliders: Vec<(Collider, Vec2)>,
+) -> impl Bundle {
+    let tile_data: Vec<Option<TileData>> = (0..size.element_product()).map(|xy| {
+        if let Some((id, _)) = tiles.iter().find(|(_, pos)| pos.x == xy % size.x && pos.y == xy / size.x) {
+            Some(TileData::from_tileset_index(*id))
+        } else { None }
+    }).collect();
+    (
+        Tilemap,
+        TilemapChunk {
+            chunk_size: size,
+            tile_display_size: TILE_DISPLAY_SIZE,
+            tileset: asset_server.load_with_settings(
+                TILEMAP_PATH,
+                |settings: &mut ImageLoaderSettings| {
+                    settings.array_layout = Some(ImageArrayLayout::RowCount { rows: 3 })
+                },
+            ),
+            ..default()
+        },
+        TilemapChunkTileData(tile_data),
+        Children::spawn(SpawnIter(colliders.into_iter()
+            .map(move |(collider, pos)| {(
+                collider.clone(),
+                Transform::from_xyz(
+                    pos.x - HALVED_PIXELS_PER_METER * size.x as f32,
+                    pos.y,
+                    0.
+                ),
+            )})
+        )),
+    )
+}