Add a responsive scaling for ui (#73)

Co-authored-by: raphael <lauray@outlook.fr>
Reviewed-on: fish-canard/border-wars#73
Reviewed-by: CoCo_Sol <solois.corentin@gmail.com>

crates/border-wars/src/lib.rs

@@ -4,6 +4,7 @@ use bevy::prelude::*;
 
 pub mod camera;
 pub mod map;
+pub mod responsive_scale;
 pub mod scenes;
 
 /// The current scene of the game.

crates/border-wars/src/responsive_scale.rs

@@ -0,0 +1,37 @@
+//! The file that contains the responsive scaling logic.
+
+use bevy::prelude::*;
+
+/// The plugin for the responsive scaling.
+pub struct ResponsiveScalingPlugin;
+
+impl Plugin for ResponsiveScalingPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_systems(Startup, init_window_size);
+        app.add_systems(Update, change_scaling);
+    }
+}
+
+/// The default window size.
+#[derive(Resource)]
+pub struct WindowSize(pub Vec2);
+
+/// Initializes the window size.
+pub fn init_window_size(mut command: Commands) {
+    command.insert_resource(WindowSize(Vec2::new(1280., 720.)));
+}
+
+/// Calculates the ui_scale.0 depending on the default screen size
+/// in order to make the screen responsive.
+pub fn change_scaling(
+    mut ui_scale: ResMut<UiScale>,
+    windows: Query<&Window>,
+    size: Res<WindowSize>,
+) {
+    let window = windows.get_single().expect("Main window not found");
+    let (a, b) = (
+        window.resolution.width() / size.0.x,
+        window.resolution.height() / size.0.y,
+    );
+    ui_scale.0 = if a < b { a } else { b } as f64
+}

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

@@ -3,7 +3,7 @@
 use bevy::prelude::*;
 use bevy_egui::EguiPlugin;
 
-use crate::CurrentScene;
+use crate::{responsive_scale, CurrentScene};
 
 pub mod lobby;
 pub mod menu;
@@ -16,6 +16,7 @@ impl Plugin for ScenesPlugin {
         app.add_plugins(EguiPlugin)
             .add_state::<CurrentScene>()
             .add_plugins(menu::MenuPlugin)
-            .add_plugins(lobby::LobbyPlugin);
+            .add_plugins(lobby::LobbyPlugin)
+            .add_plugins(responsive_scale::ResponsiveScalingPlugin);
     }
 }