Optionally restore original power scheme when window loses focus.

src/lib.rs

@@ -1,11 +1,58 @@
-use bevy::prelude::*;
+use bevy::{prelude::*, window::WindowFocused};
 #[cfg(windows)]
-use windows::Win32::System::{Power, SystemServices::GUID_MIN_POWER_SAVINGS};
+use windows::{
+    core::GUID,
+    Win32::System::{Power, SystemServices::GUID_MIN_POWER_SAVINGS},
+};
 
-fn setup() {
+#[derive(Clone, Copy, Default)]
+pub struct FullThrottleConfig {
+    pub restore_original_scheme_on_unfocus: bool,
+}
+
+#[cfg(windows)]
+#[derive(Deref, DerefMut)]
+struct DefaultScheme(GUID);
+
+#[cfg(not(windows))]
+struct DefaultScheme();
+
+#[allow(unused_mut, unused_variables)]
+fn setup(mut commands: Commands) {
     #[cfg(windows)]
     unsafe {
-        Power::PowerSetActiveScheme(None, &GUID_MIN_POWER_SAVINGS);
+        let mut active: *mut GUID = std::ptr::null_mut();
+        Power::PowerGetActiveScheme(None, &mut active);
+        if let Some(active) = active.as_ref() {
+            let scheme = DefaultScheme(*active);
+            commands.insert_resource(scheme);
+        }
+    }
+}
+
+#[allow(unused_variables)]
+fn focus_change(
+    config: Option<Res<FullThrottleConfig>>,
+    mut focus: EventReader<WindowFocused>,
+    scheme: Res<DefaultScheme>,
+) {
+    let config: FullThrottleConfig = config
+        .map(|v| *v)
+        .unwrap_or_else(|| FullThrottleConfig::default());
+    for event in focus.iter() {
+        if event.focused {
+            #[cfg(windows)]
+            unsafe {
+                Power::PowerSetActiveScheme(None, &GUID_MIN_POWER_SAVINGS);
+            }
+        } else {
+            #[cfg(windows)]
+            if config.restore_original_scheme_on_unfocus {
+                unsafe {
+                    Power::PowerSetActiveScheme(None, &**scheme);
+                }
+            }
+        }
     }
 }
 
@@ -13,6 +60,6 @@ pub struct FullThrottlePlugin;
 
 impl Plugin for FullThrottlePlugin {
     fn build(&self, app: &mut App) {
-        app.add_startup_system(setup);
+        app.add_startup_system(setup).add_system(focus_change);
     }
 }