From 8df05d923d2e77a8c510fe51136882a14a814b82 Mon Sep 17 00:00:00 2001
From: Simon Gellis <simongellis@gmail.com>
Date: Sat, 15 Feb 2025 16:55:21 -0500
Subject: [PATCH] Share one wgpu instance across all windows

---
 src/app.rs | 76 +++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 64 insertions(+), 12 deletions(-)

diff --git a/src/app.rs b/src/app.rs
index 00e358f..0de36b1 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -35,6 +35,7 @@ fn load_icon() -> anyhow::Result<IconData> {
 
 pub struct Application {
     icon: Option<Arc<IconData>>,
+    wgpu: WgpuState,
     client: EmulatorClient,
     proxy: EventLoopProxy<UserEvent>,
     mappings: MappingProvider,
@@ -51,6 +52,7 @@ impl Application {
         proxy: EventLoopProxy<UserEvent>,
         debug_port: Option<u16>,
     ) -> Self {
+        let wgpu = WgpuState::new();
         let icon = load_icon().ok().map(Arc::new);
         let persistence = Persistence::new();
         let mappings = MappingProvider::new(persistence.clone());
@@ -62,6 +64,7 @@ impl Application {
         }
         Self {
             icon,
+            wgpu,
             client,
             proxy,
             mappings,
@@ -80,7 +83,7 @@ impl Application {
         }
         self.viewports.insert(
             viewport_id,
-            Viewport::new(event_loop, self.icon.clone(), window),
+            Viewport::new(event_loop, &self.wgpu, self.icon.clone(), window),
         );
     }
 }
@@ -238,6 +241,58 @@ impl ApplicationHandler<UserEvent> for Application {
     }
 }
 
+struct WgpuState {
+    instance: Arc<wgpu::Instance>,
+    adapter: Arc<wgpu::Adapter>,
+    device: Arc<wgpu::Device>,
+    queue: Arc<wgpu::Queue>,
+}
+
+impl WgpuState {
+    fn new() -> Self {
+        let egui_wgpu::WgpuConfiguration {
+            wgpu_setup:
+                egui_wgpu::WgpuSetup::CreateNew {
+                    #[allow(unused)]
+                    supported_backends,
+                    device_descriptor,
+                    ..
+                },
+            ..
+        } = egui_wgpu::WgpuConfiguration::default()
+        else {
+            panic!("required fields not found")
+        };
+        #[cfg(windows)]
+        let supported_backends = wgpu::util::backend_bits_from_env()
+            .unwrap_or((wgpu::Backends::PRIMARY | wgpu::Backends::GL) - wgpu::Backends::VULKAN);
+        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
+            backends: supported_backends,
+            ..wgpu::InstanceDescriptor::default()
+        });
+
+        let adapter = pollster::block_on(instance.request_adapter(&wgpu::RequestAdapterOptions {
+            power_preference: wgpu::PowerPreference::HighPerformance,
+            compatible_surface: None,
+            force_fallback_adapter: false,
+        }))
+        .expect("could not create adapter");
+
+        let trace_path = std::env::var("WGPU_TRACE");
+        let (device, queue) = pollster::block_on(adapter.request_device(
+            &(*device_descriptor)(&adapter),
+            trace_path.ok().as_ref().map(std::path::Path::new),
+        ))
+        .expect("could not request device");
+        Self {
+            instance: Arc::new(instance),
+            adapter: Arc::new(adapter),
+            device: Arc::new(device),
+            queue: Arc::new(queue),
+        }
+    }
+}
+
 struct Viewport {
     painter: egui_wgpu::winit::Painter,
     ctx: Context,
@@ -251,6 +306,7 @@ struct Viewport {
 impl Viewport {
     pub fn new(
         event_loop: &ActiveEventLoop,
+        wgpu: &WgpuState,
         icon: Option<Arc<IconData>>,
         mut app: Box<dyn AppWindow>,
     ) -> Self {
@@ -274,20 +330,16 @@ impl Viewport {
         });
         egui_extras::install_image_loaders(&ctx);
 
-        #[allow(unused_mut)]
-        let mut wgpu_config = egui_wgpu::WgpuConfiguration {
+        let wgpu_config = egui_wgpu::WgpuConfiguration {
             present_mode: wgpu::PresentMode::AutoNoVsync,
+            wgpu_setup: egui_wgpu::WgpuSetup::Existing {
+                instance: wgpu.instance.clone(),
+                adapter: wgpu.adapter.clone(),
+                device: wgpu.device.clone(),
+                queue: wgpu.queue.clone(),
+            },
             ..egui_wgpu::WgpuConfiguration::default()
         };
-        #[cfg(windows)]
-        {
-            if let egui_wgpu::WgpuSetup::CreateNew {
-                supported_backends, ..
-            } = &mut wgpu_config.wgpu_setup
-            {
-                *supported_backends -= wgpu::Backends::VULKAN;
-            }
-        }
 
         let mut painter =
             egui_wgpu::winit::Painter::new(ctx.clone(), wgpu_config, 1, None, false, true);