Click-on tile handle system (#74)

Reviewed-on: fish-canard/border-wars#74
Reviewed-by: Raphaël <r.lauray@outlook.fr>

crates/border-wars/src/main.rs

@@ -2,6 +2,7 @@
 
 use bevy::prelude::*;
 use border_wars::camera::CameraPlugin;
+use border_wars::map::click_tile::TilesClickable;
 use border_wars::map::renderer::RendererPlugin;
 use border_wars::scenes::ScenesPlugin;
 
@@ -11,5 +12,6 @@ fn main() {
         .add_plugins(ScenesPlugin)
         .add_plugins(RendererPlugin)
         .add_plugins(CameraPlugin)
+        .add_plugins(TilesClickable)
         .run();
 }

crates/border-wars/src/map/click_tile.rs

@@ -0,0 +1,105 @@
+//! All programs related to the clicking on a tile.
+
+use bevy::prelude::*;
+
+use super::Tile;
+
+/// The event that is triggered when a tile is clicked.
+///
+/// The event contains the index (ID) of the clicked tile.
+#[derive(Event)]
+pub struct TileJustClicked(pub u32);
+
+/// An event that is triggered when a mouse button is clicked.
+///
+/// The event contains the position of the cursor in the world.
+#[derive(Event)]
+struct ClickOnTheWorld(Vec2);
+
+/// A zone that can't be clicked.
+/// For exemple the UI of the game.
+#[derive(Component)]
+pub struct ZoneNotClickable;
+
+/// A plugin that handles the selection of tiles.
+pub struct TilesClickable;
+
+impl Plugin for TilesClickable {
+    fn build(&self, app: &mut App) {
+        app.add_systems(PreUpdate, mouse_handler)
+            .add_systems(PreUpdate, select_closest_tile)
+            .add_event::<ClickOnTheWorld>()
+            .add_event::<TileJustClicked>();
+    }
+}
+
+/// Handles the mouse click and gets the position of the cursor in the world.
+/// Finally, it sends an event with the position of the cursor.
+fn mouse_handler(
+    mouse_button_input: Res<Input<MouseButton>>,
+    windows: Query<&Window>,
+    cameras: Query<(&Camera, &GlobalTransform)>,
+    mut events_writer: EventWriter<ClickOnTheWorld>,
+    not_clickable_zones: Query<(&Node, &GlobalTransform), With<ZoneNotClickable>>,
+    ui_scale: Res<UiScale>,
+) {
+    if !mouse_button_input.just_pressed(MouseButton::Left) {
+        return;
+    }
+
+    let window = windows.get_single().expect("Main window not found");
+
+    let cursor_position_on_screen = window.cursor_position();
+
+    let Some(cursor_position_on_screen) = cursor_position_on_screen else {
+        return;
+    };
+
+    for (node, global_transform) in not_clickable_zones.iter() {
+        let rect = node.physical_rect(global_transform, window.scale_factor(), ui_scale.0);
+        if rect.contains(cursor_position_on_screen) {
+            return;
+        }
+    }
+
+    let (camera, camera_transform) = cameras.get_single().expect("Camera not found");
+
+    let cursor_position_in_world = camera
+        .viewport_to_world(camera_transform, cursor_position_on_screen)
+        .expect("Failed to convert cursor position")
+        .origin
+        .truncate();
+
+    events_writer.send(ClickOnTheWorld(cursor_position_in_world));
+}
+
+/// Get the closest tile to the cursor and send it in an event.
+fn select_closest_tile(
+    tiles: Query<(Entity, &Transform, &Tile)>,
+    mut click_event_reader: EventReader<ClickOnTheWorld>,
+    mut clicked_tile_event_writer: EventWriter<TileJustClicked>,
+) {
+    for click_event in click_event_reader.read() {
+        // The closest tile and its distance to the cursor.
+        let mut closest_entity: Option<Entity> = None;
+        let mut closest_position: Option<f32> = None;
+
+        for (tile_entity, tile_transform, tile_type) in tiles.iter() {
+            let mut tile_position = tile_transform.translation.truncate();
+            let tile_size = tile_type.get_image_size();
+            let tile_scale = tile_transform.scale.truncate();
+
+            tile_position += (tile_size / 2.0) * tile_scale;
+
+            let distance_to_cursor = tile_position.distance(click_event.0);
+
+            if closest_position.is_none() || closest_position > Some(distance_to_cursor) {
+                closest_entity = Some(tile_entity);
+                closest_position = Some(distance_to_cursor);
+            }
+        }
+        if let Some(tile_entity) = closest_entity {
+            clicked_tile_event_writer.send(TileJustClicked(tile_entity.index()));
+        }
+    }
+}

crates/border-wars/src/map/mod.rs

@@ -1,5 +1,6 @@
 //! Contains all the logic related to the map.
 
+pub mod click_tile;
 pub mod generation;
 pub mod hex;
 pub mod renderer;

crates/border-wars/src/map/renderer.rs

@@ -40,7 +40,7 @@ impl Tile {
     ///
     /// TODO: we are currently using temporary images that will modify
     /// this function in the future.
-    const fn get_image_size(&self) -> Vec2 {
+    pub const fn get_image_size(&self) -> Vec2 {
         match self {
             Self::Grass => Vec2 { x: 184.0, y: 164.0 },
             Self::Forest => Vec2 { x: 184.0, y: 138.0 },