Add a generic hover system (#93)

Reviewed-on: fish-canard/border-wars#93
Reviewed-by: Raphaël <r.lauray@outlook.fr>
Co-authored-by: CoCo_Sol <solois.corentin@gmail.com>
Co-committed-by: CoCo_Sol <solois.corentin@gmail.com>

crates/border-wars/src/hover.rs

@@ -0,0 +1,38 @@
+//! The file that contains the hover logic.
+
+use bevy::prelude::*;
+
+/// The plugin for the hover system.
+pub struct HoverPlugin;
+
+impl Plugin for HoverPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_systems(Update, hovering);
+    }
+}
+
+/// A component that stores the hover texture and the original texture.
+#[derive(Component, Clone)]
+struct HoveredTexture {
+    /// The original texture.
+    texture: Handle<Image>,
+
+    /// The hovered texture.
+    hovered_texture: Handle<Image>,
+}
+
+/// The system that applies the hover logic by changing the texture.
+fn hovering(
+    mut interaction_query: Query<
+        (&Interaction, &HoveredTexture, &mut UiImage),
+        Changed<Interaction>,
+    >,
+) {
+    for (interaction, textures, mut image) in interaction_query.iter_mut() {
+        match *interaction {
+            Interaction::Hovered => image.texture = textures.hovered_texture.clone(),
+            Interaction::None => image.texture = textures.texture.clone(),
+            Interaction::Pressed => (),
+        }
+    }
+}

crates/border-wars/src/lib.rs

@@ -6,6 +6,7 @@ use networking::PlayerRank;
 use serde::{Deserialize, Serialize};
 
 pub mod camera;
+pub mod hover;
 pub mod map;
 pub mod networking;
 pub mod responsive_scale;