Make RequestAdapterOptions.power_preference optional (#3903)

Co-authored-by: Connor Fitzgerald <connorwadefitzgerald@gmail.com>

CHANGELOG.md

@@ -46,7 +46,8 @@ Bottom level categories:
 #### Misc Breaking Changes
 
 - Change `AdapterInfo::{device,vendor}` to be `u32` instead of `usize`. By @ameknite in [#3760](https://github.com/gfx-rs/wgpu/pull/3760)
-- Remove the `backend_bits` parameter in `initialize_adapter_from_env` and `initialize_adapter_from_env_or_default` - use [InstanceDescriptor::backends](https://docs.rs/wgpu/latest/wgpu/struct.InstanceDescriptor.html#structfield.backends) instead. By @fornwall in [#3904](https://github.com/gfx-rs/wgpu/pull/3904)
+- Remove the `backend_bits` parameter in `initialize_adapter_from_env` and `initialize_adapter_from_env_or_default` - use [InstanceDescriptor::backends](https://docs.rs/wgpu/latest/wgpu/struct.InstanceDescriptor.html#structfield.backends) instead. By @fornwall in [#3904](https://github.com/gfx-rs/wgpu/pull/3904) 
+- Make `RequestAdapterOptions.power_preference` optional. By @Aaron1011 in [#3903](https://github.com/gfx-rs/wgpu/pull/3903)
 - Add a `compatible_surface` parameter to `initialize_adapter_from_env` and use that to make `initialize_adapter_from_env_or_default` always respect its `compatible_surface` parameter. By @fornwall in [#3905](https://github.com/gfx-rs/wgpu/pull/3905)
 
 #### Vulkan

player/src/bin/play.rs

@@ -64,7 +64,7 @@ fn main() {
             let adapter = global
                 .request_adapter(
                     &wgc::instance::RequestAdapterOptions {
-                        power_preference: wgt::PowerPreference::LowPower,
+                        power_preference: wgt::PowerPreference::None,
                         force_fallback_adapter: false,
                         #[cfg(feature = "winit")]
                         compatible_surface: Some(surface),

player/tests/test.rs

@@ -193,7 +193,7 @@ impl Corpus {
             }
             let adapter = match global.request_adapter(
                 &wgc::instance::RequestAdapterOptions {
-                    power_preference: wgt::PowerPreference::LowPower,
+                    power_preference: wgt::PowerPreference::None,
                     force_fallback_adapter: false,
                     compatible_surface: None,
                 },

wgpu-core/src/instance.rs

@@ -896,6 +896,17 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
             // hardware GPU (integrated or discrete).
             PowerPreference::LowPower => integrated.or(discrete).or(other).or(virt).or(cpu),
             PowerPreference::HighPerformance => discrete.or(integrated).or(other).or(virt).or(cpu),
+            PowerPreference::None => {
+                let option_min = |a: Option<usize>, b: Option<usize>| {
+                    if let (Some(a), Some(b)) = (a, b) {
+                        Some(a.min(b))
+                    } else {
+                        a.or(b)
+                    }
+                };
+                // Pick the lowest id of these types
+                option_min(option_min(discrete, integrated), other)
+            }
         };
 
         let mut selected = preferred_gpu.unwrap_or(0);

wgpu-types/src/lib.rs

@@ -130,16 +130,18 @@ impl Backend {
 /// Corresponds to [WebGPU `GPUPowerPreference`](
 /// https://gpuweb.github.io/gpuweb/#enumdef-gpupowerpreference).
 #[repr(C)]
-#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, Hash)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Default)]
 #[cfg_attr(feature = "trace", derive(Serialize))]
 #[cfg_attr(feature = "replay", derive(Deserialize))]
 #[cfg_attr(feature = "serde", serde(rename_all = "kebab-case"))]
 pub enum PowerPreference {
-    /// Adapter that uses the least possible power. This is often an integrated GPU.
     #[default]
-    LowPower = 0,
+    /// Power usage is not considered when choosing an adapter.
+    None = 0,
+    /// Adapter that uses the least possible power. This is often an integrated GPU.
+    LowPower = 1,
     /// Adapter that has the highest performance. This is often a discrete GPU.
-    HighPerformance = 1,
+    HighPerformance = 2,
 }
 
 bitflags::bitflags! {

wgpu/src/backend/web.rs

@@ -986,10 +986,15 @@ impl crate::context::Context for Context {
         //assert!(backends.contains(wgt::Backends::BROWSER_WEBGPU));
         let mut mapped_options = web_sys::GpuRequestAdapterOptions::new();
         let mapped_power_preference = match options.power_preference {
-            wgt::PowerPreference::LowPower => web_sys::GpuPowerPreference::LowPower,
-            wgt::PowerPreference::HighPerformance => web_sys::GpuPowerPreference::HighPerformance,
+            wgt::PowerPreference::None => None,
+            wgt::PowerPreference::LowPower => Some(web_sys::GpuPowerPreference::LowPower),
+            wgt::PowerPreference::HighPerformance => {
+                Some(web_sys::GpuPowerPreference::HighPerformance)
+            }
         };
-        mapped_options.power_preference(mapped_power_preference);
+        if let Some(mapped_pref) = mapped_power_preference {
+            mapped_options.power_preference(mapped_pref);
+        }
         let adapter_promise = self.0.request_adapter_with_options(&mapped_options);
 
         MakeSendFuture::new(