Merge pull request vladbat00#64 from mvlabat/multi-threaded

Introduce mutable getters for EguiContext, feature gate immutable ones

README.md

@@ -53,11 +53,8 @@ fn main() {
         .run();
 }
 
-// Note the usage of `ResMut`. Even though `ctx` method doesn't require
-// mutability, accessing the context from different threads will result
-// into panic if you don't enable `multi_threaded` feature.
-fn ui_example(egui_context: ResMut<EguiContext>) {
-    egui::Window::new("Hello").show(egui_context.ctx(), |ui| {
+fn ui_example(mut egui_context: ResMut<EguiContext>) {
+    egui::Window::new("Hello").show(egui_context.ctx_mut(), |ui| {
         ui.label("world");
     });
 }

examples/simple.rs

@@ -9,8 +9,8 @@ fn main() {
         .run();
 }
 
-fn ui_example(egui_context: Res<EguiContext>) {
-    egui::Window::new("Hello").show(egui_context.ctx(), |ui| {
+fn ui_example(mut egui_context: ResMut<EguiContext>) {
+    egui::Window::new("Hello").show(egui_context.ctx_mut(), |ui| {
         ui.label("world");
     });
 }

examples/two_windows.rs

@@ -64,7 +64,6 @@ const SECONDARY_EGUI_PASS: &str = "secondary_egui_pass";
 
 fn create_new_window(
     mut create_window_events: EventWriter<CreateWindow>,
-
     mut commands: Commands,
     mut active_cameras: ResMut<ActiveCameras>,
 ) {
@@ -128,13 +127,13 @@ struct SharedUiState {
 }
 
 fn ui_first_window(
-    egui_context: Res<EguiContext>,
+    mut egui_context: ResMut<EguiContext>,
     mut ui_state: Local<UiState>,
     mut shared_ui_state: ResMut<SharedUiState>,
 ) {
     egui::Window::new("First Window")
         .vscroll(true)
-        .show(egui_context.ctx(), |ui| {
+        .show(egui_context.ctx_mut(), |ui| {
             ui.horizontal(|ui| {
                 ui.label("Write something: ");
                 ui.text_edit_singleline(&mut ui_state.input);
@@ -152,11 +151,11 @@ fn ui_first_window(
 }
 
 fn ui_second_window(
-    egui_context: Res<EguiContext>,
+    mut egui_context: ResMut<EguiContext>,
     mut ui_state: Local<UiState>,
     mut shared_ui_state: ResMut<SharedUiState>,
 ) {
-    let ctx = match egui_context.try_ctx_for_window(*SECOND_WINDOW_ID) {
+    let ctx = match egui_context.try_ctx_for_window_mut(*SECOND_WINDOW_ID) {
         Some(ctx) => ctx,
         None => return,
     };

examples/ui.rs

@@ -34,8 +34,8 @@ fn load_assets(mut egui_context: ResMut<EguiContext>, assets: Res<AssetServer>)
     egui_context.set_egui_texture(BEVY_TEXTURE_ID, texture_handle);
 }
 
-fn configure_visuals(egui_ctx: ResMut<EguiContext>) {
-    egui_ctx.ctx().set_visuals(egui::Visuals {
+fn configure_visuals(mut egui_ctx: ResMut<EguiContext>) {
+    egui_ctx.ctx_mut().set_visuals(egui::Visuals {
         window_corner_radius: 0.0,
         ..Default::default()
     });
@@ -72,7 +72,7 @@ fn ui_example(
 
     egui::SidePanel::left("side_panel")
         .default_width(200.0)
-        .show(egui_ctx.ctx(), |ui| {
+        .show(egui_ctx.ctx_mut(), |ui| {
             ui.heading("Side Panel");
 
             ui.horizontal(|ui| {
@@ -105,7 +105,7 @@ fn ui_example(
             });
         });
 
-    egui::TopBottomPanel::top("top_panel").show(egui_ctx.ctx(), |ui| {
+    egui::TopBottomPanel::top("top_panel").show(egui_ctx.ctx_mut(), |ui| {
         // The top panel is often a good place for a menu bar:
         egui::menu::bar(ui, |ui| {
             egui::menu::menu_button(ui, "File", |ui| {
@@ -116,7 +116,7 @@ fn ui_example(
         });
     });
 
-    egui::CentralPanel::default().show(egui_ctx.ctx(), |ui| {
+    egui::CentralPanel::default().show(egui_ctx.ctx_mut(), |ui| {
         ui.heading("Egui Template");
         ui.hyperlink("https://github.com/emilk/egui_template");
         ui.add(egui::github_link_file_line!(
@@ -140,7 +140,7 @@ fn ui_example(
 
     egui::Window::new("Window")
         .vscroll(true)
-        .show(egui_ctx.ctx(), |ui| {
+        .show(egui_ctx.ctx_mut(), |ui| {
             ui.label("Windows can be moved by dragging them.");
             ui.label("They are automatically sized based on contents.");
             ui.label("You can turn on resizing and scrolling if you like.");

src/lib.rs

@@ -31,11 +31,8 @@
 //!         .run();
 //! }
 //!
-//! // Note the usage of `ResMut`. Even though `ctx` method doesn't require
-//! // mutability, accessing the context from different threads will result
-//! // into panic if you don't enable `multi_threaded` feature.
-//! fn ui_example(egui_context: Res<EguiContext>) {
-//!     egui::Window::new("Hello").show(egui_context.ctx(), |ui| {
+//! fn ui_example(mut egui_context: ResMut<EguiContext>) {
+//!     egui::Window::new("Hello").show(egui_context.ctx_mut(), |ui| {
 //!         ui.label("world");
 //!     });
 //! }
@@ -224,19 +221,22 @@ impl EguiContext {
 
     /// Egui context of the primary window.
     ///
-    /// Note: accessing the context from different threads simultaneously requires enabling
-    /// `egui/multi_threaded` feature.
+    /// This function is only available when the `multi_threaded` feature is enabled.
+    /// The preferable way is to use `ctx_mut` to avoid unpredictable blocking inside UI systems.
+    #[cfg(feature = "multi_threaded")]
     #[track_caller]
     pub fn ctx(&self) -> &egui::CtxRef {
         self.ctx.get(&WindowId::primary()).expect("`EguiContext::ctx` was called for an uninitialized context (primary window), consider moving your startup system to `StartupStage::Startup` stage or run it after `EguiStartupSystem::InitContexts` system")
     }
 
     /// Egui context for a specific window.
-    /// If you want to display UI on a non-primary window,
-    /// make sure to set up the render graph by calling [`setup_pipeline`].
+    /// If you want to display UI on a non-primary window, make sure to set up the render graph by
+    /// calling [`setup_pipeline`].
     ///
-    /// Note: accessing the context from different threads simultaneously requires enabling
-    /// `egui/multi_threaded` feature.
+    /// This function is only available when the `multi_threaded` feature is enabled.
+    /// The preferable way is to use `ctx_for_window_mut` to avoid unpredictable blocking inside UI
+    /// systems.
+    #[cfg(feature = "multi_threaded")]
     #[track_caller]
     pub fn ctx_for_window(&self, window: WindowId) -> &egui::CtxRef {
         self.ctx
@@ -245,11 +245,40 @@ impl EguiContext {
             .unwrap()
     }
 
-    /// Fallible variant of [`EguiContext::ctx_for_window`]. Make sure to set up the render graph by calling [`setup_pipeline`].
+    /// Fallible variant of [`EguiContext::ctx_for_window`]. Make sure to set up the render graph by
+    /// calling [`setup_pipeline`].
+    ///
+    /// This function is only available when the `multi_threaded` feature is enabled.
+    /// The preferable way is to use `try_ctx_for_window_mut` to avoid unpredictable blocking inside
+    /// UI systems.
+    #[cfg(feature = "multi_threaded")]
     pub fn try_ctx_for_window(&self, window: WindowId) -> Option<&egui::CtxRef> {
         self.ctx.get(&window)
     }
 
+    /// Egui context of the primary window.
+    #[track_caller]
+    pub fn ctx_mut(&mut self) -> &egui::CtxRef {
+        self.ctx.get(&WindowId::primary()).expect("`EguiContext::ctx_mut` was called for an uninitialized context (primary window), consider moving your startup system to `StartupStage::Startup` stage or run it after `EguiStartupSystem::InitContexts` system")
+    }
+
+    /// Egui context for a specific window.
+    /// If you want to display UI on a non-primary window, make sure to set up the render graph by
+    /// calling [`setup_pipeline`].
+    #[track_caller]
+    pub fn ctx_for_window_mut(&mut self, window: WindowId) -> &egui::CtxRef {
+        self.ctx
+            .get(&window)
+            .ok_or_else(|| format!("`EguiContext::ctx_for_window_mut` was called for an uninitialized context (window {}), consider moving your UI system to `CoreStage::Update` or run it after `EguiSystem::BeginFrame` system (`StartupStage::Startup` or `EguiStartupSystem::InitContexts` for startup systems respectively)", window))
+            .unwrap()
+    }
+
+    /// Fallible variant of [`EguiContext::ctx_for_window_mut`]. Make sure to set up the render
+    /// graph by calling [`setup_pipeline`].
+    pub fn try_ctx_for_window_mut(&mut self, window: WindowId) -> Option<&egui::CtxRef> {
+        self.ctx.get(&window)
+    }
+
     /// Can accept either a strong or a weak handle.
     ///
     /// You may want to pass a weak handle if you control removing texture assets in your

src/systems.rs

@@ -334,24 +334,25 @@ pub fn begin_frame(
 }
 
 pub fn process_output(
-    egui_context: Res<EguiContext>,
+    mut egui_context: ResMut<EguiContext>,
     mut egui_output: ResMut<HashMap<WindowId, EguiOutput>>,
     mut egui_shapes: ResMut<HashMap<WindowId, EguiShapes>>,
     #[cfg(feature = "manage_clipboard")] mut egui_clipboard: ResMut<crate::EguiClipboard>,
     winit_windows: Option<Res<WinitWindows>>,
 ) {
-    for id in egui_context.ctx.keys().copied() {
-        let (output, shapes) = egui_context.ctx_for_window(id).end_frame();
-        egui_shapes.entry(id).or_default().shapes = shapes;
-        egui_output.entry(id).or_default().output = output.clone();
+    let window_ids: Vec<_> = egui_context.ctx.keys().copied().collect();
+    for window_id in window_ids {
+        let (output, shapes) = egui_context.ctx_for_window_mut(window_id).end_frame();
+        egui_shapes.entry(window_id).or_default().shapes = shapes;
+        egui_output.entry(window_id).or_default().output = output.clone();
 
         #[cfg(feature = "manage_clipboard")]
         if !output.copied_text.is_empty() {
             egui_clipboard.set_contents(&output.copied_text);
         }
 
         if let Some(ref winit_windows) = winit_windows {
-            if let Some(winit_window) = winit_windows.get_window(id) {
+            if let Some(winit_window) = winit_windows.get_window(window_id) {
                 winit_window.set_cursor_icon(
                     egui_to_winit_cursor_icon(output.cursor_icon)
                         .unwrap_or(winit::window::CursorIcon::Default),