Add a render thread

The default event loop on winit, at least on Windows is too slow. See
rust-windowing/winit#2782

src/renderer/cursor_renderer/mod.rs

@@ -13,6 +13,7 @@ use crate::{
     renderer::animation_utils::*,
     renderer::{GridRenderer, RenderedWindow},
     settings::{ParseFromValue, SETTINGS},
+    window::UserEvent,
 };
 
 use blink::*;
@@ -198,7 +199,7 @@ impl CursorRenderer {
         renderer
     }
 
-    pub fn handle_event(&mut self, event: &Event<()>) {
+    pub fn handle_event(&mut self, event: &Event<UserEvent>) {
         if let Event::WindowEvent {
             event: WindowEvent::Focused(is_focused),
             ..

src/renderer/mod.rs

@@ -23,6 +23,7 @@ use crate::{
     event_aggregator::EVENT_AGGREGATOR,
     profiling::tracy_zone,
     settings::*,
+    window::UserEvent,
     WindowSettings,
 };
 
@@ -130,7 +131,7 @@ impl Renderer {
         }
     }
 
-    pub fn handle_event(&mut self, event: &Event<()>) {
+    pub fn handle_event(&mut self, event: &Event<UserEvent>) {
         self.cursor_renderer.handle_event(event);
     }
 

src/window/keyboard_manager.rs

@@ -2,6 +2,8 @@ use crate::{
     bridge::{SerialCommand, UiCommand},
     event_aggregator::EVENT_AGGREGATOR,
 };
+
+use crate::window::UserEvent;
 #[cfg(target_os = "macos")]
 use crate::{settings::SETTINGS, window::KeyboardSettings};
 #[allow(unused_imports)]
@@ -24,7 +26,7 @@ impl KeyboardManager {
         }
     }
 
-    pub fn handle_event(&mut self, event: &Event<()>) {
+    pub fn handle_event(&mut self, event: &Event<UserEvent>) {
         match event {
             Event::WindowEvent {
                 event:

src/window/mod.rs

@@ -12,7 +12,7 @@ mod draw_background;
 use std::env;
 
 use winit::{
-    event_loop::EventLoop,
+    event_loop::EventLoopBuilder,
     window::{Icon, WindowBuilder},
 };
 
@@ -27,6 +27,17 @@ use winit::platform::wayland::WindowBuilderExtWayland;
 #[cfg(target_os = "linux")]
 use winit::platform::x11::WindowBuilderExtX11;
 
+#[cfg(target_os = "windows")]
+use std::{
+    sync::mpsc::{channel, RecvTimeoutError, TryRecvError},
+    thread,
+};
+#[cfg(target_os = "windows")]
+use winit::{
+    event::{Event, WindowEvent},
+    event_loop::ControlFlow,
+};
+
 use image::{load_from_memory, GenericImageView, Pixel};
 use keyboard_manager::KeyboardManager;
 use mouse_manager::MouseManager;
@@ -37,9 +48,9 @@ use window_wrapper::WinitWindowWrapper;
 use crate::{
     cmd_line::CmdLineSettings,
     frame::Frame,
-    profiling::tracy_create_gpu_context,
     renderer::build_window,
-    settings::{load_last_window_settings, PersistentWindowSettings, SETTINGS},
+    running_tracker::*,
+    settings::{load_last_window_settings, save_window_size, PersistentWindowSettings, SETTINGS},
 };
 pub use settings::{KeyboardSettings, WindowSettings};
 
@@ -52,6 +63,13 @@ pub enum WindowCommand {
     ListAvailableFonts,
 }
 
+
+#[allow(dead_code)]
+#[derive(Clone, Debug)]
+pub enum UserEvent {
+    ScaleFactorChanged(f64),
+}
+
 pub fn create_window() {
     let icon = {
         let icon = load_from_memory(ICON).expect("Failed to parse icon data");
@@ -63,7 +81,7 @@ pub fn create_window() {
         Icon::from_rgba(rgba, width, height).expect("Failed to create icon object")
     };
 
-    let event_loop = EventLoop::new();
+    let event_loop = EventLoopBuilder::<UserEvent>::with_user_event().build();
 
     let cmd_line_settings = SETTINGS.get::<CmdLineSettings>();
 
@@ -131,19 +149,107 @@ pub fn create_window() {
     let winit_window_builder = winit_window_builder.with_accepts_first_mouse(false);
 
     let (window, config) = build_window(winit_window_builder, &event_loop);
-    let mut window_wrapper = WinitWindowWrapper::new(
-        window,
-        config,
-        &cmd_line_settings,
-        previous_position,
-        maximized,
-    );
 
-    tracy_create_gpu_context("main_render_context");
+    // Use a render thread on Windows to work around performance issues with Winit
+    // see: https://github.com/rust-windowing/winit/issues/2782
+    #[cfg(target_os = "windows")]
+    {
+        let (txtemp, rx) = channel::<Event<UserEvent>>();
+        let mut tx = Some(txtemp);
+        let mut render_thread_handle = Some(thread::spawn(move || {
+            let mut window_wrapper = WinitWindowWrapper::new(
+                window,
+                config,
+                &cmd_line_settings,
+                previous_position,
+                maximized,
+            );
+            let mut update_loop = UpdateLoop::new(cmd_line_settings.idle);
+            #[allow(unused_assignments)]
+            loop {
+                let (wait_duration, _) = update_loop.get_event_wait_time();
+                let event = if wait_duration.as_nanos() == 0 {
+                    rx.try_recv()
+                        .map_err(|e| matches!(e, TryRecvError::Disconnected))
+                } else {
+                    rx.recv_timeout(wait_duration)
+                        .map_err(|e| matches!(e, RecvTimeoutError::Disconnected))
+                };
+
+                if update_loop.step(&mut window_wrapper, event).is_err() {
+                    break;
+                }
+            }
+            let window = window_wrapper.windowed_context.window();
+            save_window_size(
+                window.is_maximized(),
+                window.inner_size(),
+                window.outer_position().ok(),
+            );
+            std::process::exit(RUNNING_TRACKER.exit_code());
+        }));
+
+        event_loop.run(move |e, _window_target, control_flow| {
+            let e = match e {
+                Event::WindowEvent {
+                    event: WindowEvent::ScaleFactorChanged { scale_factor, .. },
+                    ..
+                } => {
+                    // It's really unfortunate that we have to do this, but
+                    // https://github.com/rust-windowing/winit/issues/1387
+                    Some(Event::UserEvent(UserEvent::ScaleFactorChanged(
+                        scale_factor,
+                    )))
+                }
+                Event::MainEventsCleared => None,
+                _ => {
+                    // With the current Winit version, all events, except ScaleFactorChanged are static
+                    Some(e.to_static().expect("Unexpected event received"))
+                }
+            };
+            if let Some(e) = e {
+                let _ = tx.as_ref().unwrap().send(e);
+            }
 
-    let mut update_loop = UpdateLoop::new(cmd_line_settings.idle);
+            if !RUNNING_TRACKER.is_running() {
+                let tx = tx.take().unwrap();
+                drop(tx);
+                let handle = render_thread_handle.take().unwrap();
+                handle.join().unwrap();
+            }
+            // We need to wake up regularly to check the running tracker, so that we can exit
+            *control_flow = ControlFlow::WaitUntil(
+                std::time::Instant::now() + std::time::Duration::from_millis(100),
+            );
+        });
+    }
 
-    event_loop.run(move |e, _window_target, control_flow| {
-        *control_flow = update_loop.step(&mut window_wrapper, e);
-    });
+    #[cfg(not(target_os = "windows"))]
+    {
+        let mut window_wrapper = WinitWindowWrapper::new(
+            window,
+            config,
+            &cmd_line_settings,
+            previous_position,
+            maximized,
+        );
+
+        let mut update_loop = UpdateLoop::new(cmd_line_settings.idle);
+
+        event_loop.run(move |e, _window_target, control_flow| {
+            *control_flow = update_loop.step(&mut window_wrapper, Ok(e)).unwrap();
+
+            if !RUNNING_TRACKER.is_running() {
+                let window = window_wrapper.windowed_context.window();
+                save_window_size(
+                    window.is_maximized(),
+                    window.inner_size(),
+                    window.outer_position().ok(),
+                );
+
+                std::process::exit(RUNNING_TRACKER.exit_code());
+            }
+
+        });
+    }
 }

src/window/mouse_manager.rs

@@ -20,7 +20,7 @@ use crate::{
     renderer::{Renderer, WindowDrawDetails},
     settings::SETTINGS,
     window::keyboard_manager::KeyboardManager,
-    window::WindowSettings,
+    window::{UserEvent, WindowSettings},
 };
 
 fn clamp_position(
@@ -422,7 +422,7 @@ impl MouseManager {
 
     pub fn handle_event(
         &mut self,
-        event: &Event<()>,
+        event: &Event<UserEvent>,
         keyboard_manager: &KeyboardManager,
         renderer: &Renderer,
         window: &Window,

src/window/update_loop.rs

@@ -8,11 +8,10 @@ use winit::{
 
 #[cfg(target_os = "macos")]
 use super::draw_background;
-use super::{WindowSettings, WinitWindowWrapper};
+use super::{UserEvent, WindowSettings, WinitWindowWrapper};
 use crate::{
     profiling::{tracy_create_gpu_context, tracy_zone},
-    running_tracker::*,
-    settings::{save_window_size, SETTINGS},
+    settings::SETTINGS,
 };
 
 enum FocusedState {
@@ -55,7 +54,7 @@ impl UpdateLoop {
         }
     }
 
-    fn get_event_deadline(&self) -> Instant {
+    pub fn get_event_wait_time(&self) -> (Duration, Instant) {
         let refresh_rate = match self.focused {
             FocusedState::Focused | FocusedState::UnfocusedNotDrawn => {
                 SETTINGS.get::<WindowSettings>().refresh_rate as f32
@@ -65,29 +64,38 @@ impl UpdateLoop {
         .max(1.0);
 
         let expected_frame_duration = Duration::from_secs_f32(1.0 / refresh_rate);
-        self.previous_frame_start + expected_frame_duration
+        if self.num_consecutive_rendered > 0 {
+            (Duration::from_nanos(0), Instant::now())
+        } else {
+            let deadline = self.previous_frame_start + expected_frame_duration;
+            (deadline.saturating_duration_since(Instant::now()), deadline)
+        }
     }
 
     pub fn step(
         &mut self,
         window_wrapper: &mut WinitWindowWrapper,
-        event: Event<()>,
-    ) -> ControlFlow {
+        event: Result<Event<UserEvent>, bool>,
+    ) -> Result<ControlFlow, ()> {
         tracy_zone!("render loop", 0);
 
         match event {
             // Window focus changed
-            Event::WindowEvent {
+            Ok(Event::WindowEvent {
                 event: WindowEvent::Focused(focused_event),
                 ..
-            } => {
+            }) => {
                 self.focused = if focused_event {
                     FocusedState::Focused
                 } else {
                     FocusedState::UnfocusedNotDrawn
                 };
             }
-            Event::MainEventsCleared => {
+            Err(true) => {
+                // Disconnected
+                return Err(());
+            }
+            Err(false) | Ok(Event::MainEventsCleared) => {
                 let dt = if self.num_consecutive_rendered > 0
                     && self.frame_dt_avg.get_num_samples() > 0
                 {
@@ -123,28 +131,21 @@ impl UpdateLoop {
                 #[cfg(target_os = "macos")]
                 draw_background(window_wrapper.windowed_context.window());
             }
-            _ => (),
+            _ => {}
         }
+        window_wrapper.handle_window_commands();
+        window_wrapper.synchronize_settings();
 
-        if !RUNNING_TRACKER.is_running() {
-            let window = window_wrapper.windowed_context.window();
-            save_window_size(
-                window.is_maximized(),
-                window.inner_size(),
-                window.outer_position().ok(),
-            );
-
-            std::process::exit(RUNNING_TRACKER.exit_code());
+        if let Ok(event) = event {
+            self.should_render |= window_wrapper.handle_event(event);
         }
 
-        window_wrapper.handle_window_commands();
-        window_wrapper.synchronize_settings();
-        self.should_render |= window_wrapper.handle_event(event);
+        let (_, deadline) = self.get_event_wait_time();
 
         if self.num_consecutive_rendered > 0 {
-            ControlFlow::Poll
+            Ok(ControlFlow::Poll)
         } else {
-            ControlFlow::WaitUntil(self.get_event_deadline())
+            Ok(ControlFlow::WaitUntil(deadline))
         }
     }
 }