add RateLimited option

Author: maniwani

crates/bevy_winit/src/lib.rs

@@ -580,6 +580,9 @@ pub fn winit_runner(mut app: App) {
                     let focused = windows.iter().any(|window| window.focused);
                     let should_update = match config.update_mode(focused) {
                         UpdateMode::Continuous => true,
+                        UpdateMode::RateLimited { .. } => {
+                            runner_state.timeout_elapsed || runner_state.redraw_requested
+                        }
                         UpdateMode::Reactive { .. } => {
                             runner_state.timeout_elapsed
                                 || runner_state.redraw_requested
@@ -608,7 +611,8 @@ pub fn winit_runner(mut app: App) {
                         let focused = windows.iter().any(|window| window.focused);
                         match config.update_mode(focused) {
                             UpdateMode::Continuous => *control_flow = ControlFlow::Poll,
-                            UpdateMode::Reactive { wait }
+                            UpdateMode::RateLimited { wait }
+                            | UpdateMode::Reactive { wait }
                             | UpdateMode::ReactiveLowPower { wait } => {
                                 if let Some(next) = runner_state.last_update.checked_add(*wait) {
                                     runner_state.scheduled_update = Some(next);

crates/bevy_winit/src/winit_config.rs

@@ -37,8 +37,17 @@ pub struct WinitSettings {
 
 impl WinitSettings {
     /// Default settings for games.
+    ///
+    /// [`Continuous`](UpdateMode::Continuous) if windows have focus,
+    /// [`RateLimited`](UpdateMode::RateLimited) otherwise.
     pub fn game() -> Self {
-        WinitSettings::default()
+        WinitSettings {
+            focused_mode: UpdateMode::Continuous,
+            unfocused_mode: UpdateMode::RateLimited {
+                wait: Duration::from_millis(50), // 20Hz
+            },
+            ..Default::default()
+        }
     }
 
     /// Default settings for desktop applications.
@@ -94,6 +103,17 @@ pub enum UpdateMode {
     /// until an [`AppExit`](bevy_app::AppExit) event appears:
     /// - enough time has elapsed since the previous update
     /// - a redraw is requested
+    RateLimited {
+        /// The minimum time to wait from the start of one update to the next.
+        ///
+        /// **Note:** This has no upper limit.
+        /// Bevy will wait forever if you set this to [`Duration::MAX`].
+        wait: Duration,
+    },
+    /// The [`App`](bevy_app::App) will update in response to the following,
+    /// until an [`AppExit`](bevy_app::AppExit) event appears:
+    /// - enough time has elapsed since the previous update
+    /// - a redraw is requested
     /// - new window or device events have appeared
     Reactive {
         /// The minimum time from the start of one update to the next.