Add WgpuConfiguration::desired_maximum_frame_latency, default to 1

This should lead to lower latency in wgpu apps
emilk · Jan 23, 2024 · 2bb7b30 · 2bb7b30
1 parent aa22704
commit 2bb7b30
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Showing 2 changed files with 29 additions and 12 deletions.
diff --git a/crates/egui-wgpu/src/lib.rs b/crates/egui-wgpu/src/lib.rs
@@ -228,6 +228,13 @@ pub struct WgpuConfiguration {
     /// Present mode used for the primary surface.
     pub present_mode: wgpu::PresentMode,
 
+    /// Desired maximum number of frames that the presentation engine should queue in advance.
+    ///
+    /// Use `1` for low-latency, and `2` for high-throughput.
+    ///
+    /// See [`wgpu::SurfaceConfiguration::desired_num_frames`] for details.
+    pub desired_maximum_frame_latency: u32,
+
     /// Power preference for the adapter.
     pub power_preference: wgpu::PowerPreference,
 
@@ -237,10 +244,22 @@ pub struct WgpuConfiguration {
 
 impl std::fmt::Debug for WgpuConfiguration {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self {
+            supported_backends,
+            device_descriptor: _,
+            present_mode,
+            desired_maximum_frame_latency,
+            power_preference,
+            on_surface_error: _,
+        } = self;
         f.debug_struct("WgpuConfiguration")
-            .field("supported_backends", &self.supported_backends)
-            .field("present_mode", &self.present_mode)
-            .field("power_preference", &self.power_preference)
+            .field("supported_backends", &supported_backends)
+            .field("present_mode", &present_mode)
+            .field(
+                "desired_maximum_frame_latency",
+                &desired_maximum_frame_latency,
+            )
+            .field("power_preference", &power_preference)
             .finish_non_exhaustive()
     }
 }
@@ -274,6 +293,8 @@ impl Default for WgpuConfiguration {
 
             present_mode: wgpu::PresentMode::AutoVsync,
 
+            desired_maximum_frame_latency: 1, // 1 = low-latency; good for GUIs.
+
             power_preference: wgpu::util::power_preference_from_env()
                 .unwrap_or(wgpu::PowerPreference::HighPerformance),
 

diff --git a/crates/egui-wgpu/src/winit.rs b/crates/egui-wgpu/src/winit.rs
@@ -142,7 +142,7 @@ impl Painter {
     fn configure_surface(
         surface_state: &SurfaceState,
         render_state: &RenderState,
-        present_mode: wgpu::PresentMode,
+        config: &WgpuConfiguration,
     ) {
         crate::profile_function!();
 
@@ -158,10 +158,10 @@ impl Painter {
         surface_state.surface.configure(
             &render_state.device,
             &wgpu::SurfaceConfiguration {
-                // TODO(emilk): expose `desired_maximum_frame_latency` to eframe users
                 usage,
                 format: render_state.target_format,
-                present_mode,
+                present_mode: config.present_mode,
+                desired_maximum_frame_latency: config.desired_maximum_frame_latency,
                 alpha_mode: surface_state.alpha_mode,
                 view_formats: vec![render_state.target_format],
                 ..surface_state
@@ -328,7 +328,7 @@ impl Painter {
         surface_state.width = width;
         surface_state.height = height;
 
-        Self::configure_surface(surface_state, render_state, self.configuration.present_mode);
+        Self::configure_surface(surface_state, render_state, &self.configuration);
 
         if let Some(depth_format) = self.depth_format {
             self.depth_texture_view.insert(
@@ -525,11 +525,7 @@ impl Painter {
             Ok(frame) => frame,
             Err(err) => match (*self.configuration.on_surface_error)(err) {
                 SurfaceErrorAction::RecreateSurface => {
-                    Self::configure_surface(
-                        surface_state,
-                        render_state,
-                        self.configuration.present_mode,
-                    );
+                    Self::configure_surface(surface_state, render_state, &self.configuration);
                     return None;
                 }
                 SurfaceErrorAction::SkipFrame => {