Add Gamepads resource (#3257)

# Objective

Fixes #3245 

## Solution

- Move GamepadLobby to lib
- Add connection_system to InputPlugin
- Updated gamepad_input example


Co-authored-by: CrazyRoka <rokarostuk@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>

crates/bevy_input/src/gamepad.rs

@@ -1,12 +1,42 @@
 use crate::{Axis, Input};
 use bevy_app::{EventReader, EventWriter};
 use bevy_ecs::system::{Res, ResMut};
-use bevy_utils::HashMap;
+use bevy_utils::{tracing::info, HashMap, HashSet};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 #[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
 pub struct Gamepad(pub usize);
 
+#[derive(Default)]
+/// Container of unique connected [Gamepad]s
+///
+/// [Gamepad]s are registered and deregistered in [gamepad_connection_system]
+pub struct Gamepads {
+    gamepads: HashSet<Gamepad>,
+}
+
+impl Gamepads {
+    /// Returns true if the [Gamepads] contains a [Gamepad].
+    pub fn contains(&self, gamepad: &Gamepad) -> bool {
+        self.gamepads.contains(gamepad)
+    }
+
+    /// Iterates over registered [Gamepad]s
+    pub fn iter(&self) -> impl Iterator {
+        self.gamepads.iter()
+    }
+
+    /// Registers [Gamepad].
+    fn register(&mut self, gamepad: Gamepad) {
+        self.gamepads.insert(gamepad);
+    }
+
+    /// Deregisters [Gamepad.
+    fn deregister(&mut self, gamepad: &Gamepad) {
+        self.gamepads.remove(gamepad);
+    }
+}
+
 #[derive(Debug, Clone, PartialEq)]
 #[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
 pub enum GamepadEventType {
@@ -204,6 +234,28 @@ impl ButtonAxisSettings {
     }
 }
 
+/// Monitors gamepad connection and disconnection events, updating the [GamepadLobby] resource accordingly
+///
+/// By default, runs during `CoreStage::PreUpdate` when added via [InputPlugin].
+pub fn gamepad_connection_system(
+    mut gamepads: ResMut<Gamepads>,
+    mut gamepad_event: EventReader<GamepadEvent>,
+) {
+    for event in gamepad_event.iter() {
+        match &event {
+            GamepadEvent(gamepad, GamepadEventType::Connected) => {
+                gamepads.register(*gamepad);
+                info!("{:?} Connected", gamepad);
+            }
+            GamepadEvent(gamepad, GamepadEventType::Disconnected) => {
+                gamepads.deregister(gamepad);
+                info!("{:?} Disconnected", gamepad);
+            }
+            _ => (),
+        }
+    }
+}
+
 pub fn gamepad_event_system(
     mut button_input: ResMut<Input<GamepadButton>>,
     mut axis: ResMut<Axis<GamepadAxis>>,

crates/bevy_input/src/lib.rs

@@ -15,7 +15,7 @@ pub mod prelude {
     pub use crate::{
         gamepad::{
             Gamepad, GamepadAxis, GamepadAxisType, GamepadButton, GamepadButtonType, GamepadEvent,
-            GamepadEventType,
+            GamepadEventType, Gamepads,
         },
         keyboard::KeyCode,
         mouse::MouseButton,
@@ -27,11 +27,12 @@ pub mod prelude {
 use bevy_app::prelude::*;
 use keyboard::{keyboard_input_system, KeyCode, KeyboardInput};
 use mouse::{mouse_button_input_system, MouseButton, MouseButtonInput, MouseMotion, MouseWheel};
+use prelude::Gamepads;
 use touch::{touch_screen_input_system, TouchInput, Touches};
 
 use gamepad::{
-    gamepad_event_system, GamepadAxis, GamepadButton, GamepadEvent, GamepadEventRaw,
-    GamepadSettings,
+    gamepad_connection_system, gamepad_event_system, GamepadAxis, GamepadButton, GamepadEvent,
+    GamepadEventRaw, GamepadSettings,
 };
 
 /// Adds keyboard and mouse input to an App
@@ -64,13 +65,18 @@ impl Plugin for InputPlugin {
             .add_event::<GamepadEvent>()
             .add_event::<GamepadEventRaw>()
             .init_resource::<GamepadSettings>()
+            .init_resource::<Gamepads>()
             .init_resource::<Input<GamepadButton>>()
             .init_resource::<Axis<GamepadAxis>>()
             .init_resource::<Axis<GamepadButton>>()
             .add_system_to_stage(
                 CoreStage::PreUpdate,
                 gamepad_event_system.label(InputSystem),
             )
+            .add_system_to_stage(
+                CoreStage::PreUpdate,
+                gamepad_connection_system.label(InputSystem),
+            )
             // touch
             .add_event::<TouchInput>()
             .init_resource::<Touches>()

examples/input/gamepad_input.rs

@@ -1,49 +1,19 @@
-use bevy::{
-    input::gamepad::{Gamepad, GamepadButton, GamepadEvent, GamepadEventType},
-    prelude::*,
-    utils::HashSet,
-};
+use bevy::{input::gamepad::GamepadButton, prelude::*};
 
 fn main() {
     App::new()
         .add_plugins(DefaultPlugins)
-        .init_resource::<GamepadLobby>()
-        .add_system_to_stage(CoreStage::PreUpdate, connection_system)
         .add_system(gamepad_system)
         .run();
 }
 
-#[derive(Default)]
-struct GamepadLobby {
-    gamepads: HashSet<Gamepad>,
-}
-
-fn connection_system(
-    mut lobby: ResMut<GamepadLobby>,
-    mut gamepad_event: EventReader<GamepadEvent>,
-) {
-    for event in gamepad_event.iter() {
-        match &event {
-            GamepadEvent(gamepad, GamepadEventType::Connected) => {
-                lobby.gamepads.insert(*gamepad);
-                info!("{:?} Connected", gamepad);
-            }
-            GamepadEvent(gamepad, GamepadEventType::Disconnected) => {
-                lobby.gamepads.remove(gamepad);
-                info!("{:?} Disconnected", gamepad);
-            }
-            _ => (),
-        }
-    }
-}
-
 fn gamepad_system(
-    lobby: Res<GamepadLobby>,
+    gamepads: Res<Gamepads>,
     button_inputs: Res<Input<GamepadButton>>,
     button_axes: Res<Axis<GamepadButton>>,
     axes: Res<Axis<GamepadAxis>>,
 ) {
-    for gamepad in lobby.gamepads.iter().cloned() {
+    for gamepad in gamepads.iter().cloned() {
         if button_inputs.just_pressed(GamepadButton(gamepad, GamepadButtonType::South)) {
             info!("{:?} just pressed South", gamepad);
         } else if button_inputs.just_released(GamepadButton(gamepad, GamepadButtonType::South)) {