Low power default option [#366]

crates/bevy_wgpu/src/lib.rs

@@ -20,7 +20,7 @@ pub struct WgpuPlugin;
 
 impl Plugin for WgpuPlugin {
     fn build(&self, app: &mut AppBuilder) {
-        let render_system = wgpu_render_system(app.resources_mut());
+        let render_system = get_wgpu_render_system(app.resources_mut());
         app.add_system_to_stage(
             bevy_render::stage::RENDER,
             render_system.thread_local_system(),
@@ -32,12 +32,33 @@ impl Plugin for WgpuPlugin {
     }
 }
 
-pub fn wgpu_render_system(resources: &mut Resources) -> impl FnMut(&mut World, &mut Resources) {
-    let mut wgpu_renderer = future::block_on(WgpuRenderer::new());
+pub fn get_wgpu_render_system(resources: &mut Resources) -> impl FnMut(&mut World, &mut Resources) {
+    let options = resources
+        .get_cloned::<WgpuOptions>()
+        .unwrap_or_else(WgpuOptions::default);
+    let mut wgpu_renderer = future::block_on(WgpuRenderer::new(options));
     let resource_context = WgpuRenderResourceContext::new(wgpu_renderer.device.clone());
     resources.insert::<Box<dyn RenderResourceContext>>(Box::new(resource_context.clone()));
     resources.insert(SharedBuffers::new(Box::new(resource_context)));
     move |world, resources| {
         wgpu_renderer.update(world, resources);
     }
 }
+
+#[derive(Default, Clone)]
+pub struct WgpuOptions {
+    power_pref: WgpuPowerOptions,
+}
+
+#[derive(Clone)]
+pub enum WgpuPowerOptions {
+    HighPerformance,
+    Adaptive,
+    LowPower,
+}
+
+impl Default for WgpuPowerOptions {
+    fn default() -> Self {
+        WgpuPowerOptions::HighPerformance
+    }
+}

crates/bevy_wgpu/src/wgpu_renderer.rs

@@ -1,4 +1,7 @@
-use crate::renderer::{WgpuRenderGraphExecutor, WgpuRenderResourceContext};
+use crate::{
+    renderer::{WgpuRenderGraphExecutor, WgpuRenderResourceContext},
+    WgpuOptions, WgpuPowerOptions,
+};
 use bevy_app::prelude::*;
 use bevy_ecs::{Resources, World};
 use bevy_render::{
@@ -18,11 +21,16 @@ pub struct WgpuRenderer {
 }
 
 impl WgpuRenderer {
-    pub async fn new() -> Self {
+    pub async fn new(options: WgpuOptions) -> Self {
         let instance = wgpu::Instance::new(wgpu::BackendBit::PRIMARY);
+
         let adapter = instance
             .request_adapter(&wgpu::RequestAdapterOptions {
-                power_preference: wgpu::PowerPreference::HighPerformance,
+                power_preference: match options.power_pref {
+                    WgpuPowerOptions::HighPerformance => wgpu::PowerPreference::HighPerformance,
+                    WgpuPowerOptions::Adaptive => wgpu::PowerPreference::Default,
+                    WgpuPowerOptions::LowPower => wgpu::PowerPreference::LowPower,
+                },
                 compatible_surface: None,
             })
             .await