Show how to close a child viewport in the example

crates/eframe/src/epi/mod.rs

@@ -123,6 +123,7 @@ pub trait App {
     ///
     /// This is called for the root viewport ([`egui::ViewportId::ROOT`]).
     /// Use [`egui::Context::show_viewport`] to spawn additional viewports (windows).
+    /// (A "viewport" in egui means an native OS window).
     fn update(&mut self, ctx: &egui::Context, frame: &mut Frame);
 
     /// Get a handle to the app.

crates/eframe/src/native/epi_integration.rs

@@ -85,7 +85,7 @@ pub fn window_builder<E>(
         ..
     } = native_options;
 
-    let mut viewport_builder = egui::ViewportBuilder::ROOT
+    let mut viewport_builder = egui::ViewportBuilder::DEFAULTS
         .with_title(title)
         .with_decorations(*decorated)
         .with_fullscreen(*fullscreen)

crates/egui-winit/src/lib.rs

@@ -201,18 +201,16 @@ impl State {
         let screen_size_in_pixels = screen_size_in_pixels(window);
         let screen_size_in_points = screen_size_in_pixels / pixels_per_point;
 
-        let getting_info = !window.is_minimized().unwrap_or_else(|| {
+        self.egui_input.screen_rect = (screen_size_in_points.x > 0.0
-            eprintln!("Cannot determine the Viewport/native window minimized state");
+            && screen_size_in_points.y > 0.0)
-            true
+            .then(|| Rect::from_min_size(Pos2::ZERO, screen_size_in_points));
-        });
 
-        self.egui_input.screen_rect = if getting_info {
+        let has_a_position = match window.is_minimized() {
-            Some(egui::Rect::from_min_size(Pos2::ZERO, screen_size_in_points))
+            None | Some(true) => false,
-        } else {
+            Some(false) => true,
-            None
         };
 
-        let inner_pos_px = if getting_info {
+        let inner_pos_px = if has_a_position {
             window
                 .inner_position()
                 .map(|pos| Pos2::new(pos.x as f32, pos.y as f32))
@@ -221,7 +219,7 @@ impl State {
             None
         };
 
-        let outer_pos_px = if getting_info {
+        let outer_pos_px = if has_a_position {
             window
                 .outer_position()
                 .map(|pos| Pos2::new(pos.x as f32, pos.y as f32))
@@ -230,14 +228,14 @@ impl State {
             None
         };
 
-        let inner_size_px = if getting_info {
+        let inner_size_px = if has_a_position {
             let size = window.inner_size();
             Some(Vec2::new(size.width as f32, size.height as f32))
         } else {
             None
         };
 
-        let outer_size_px = if getting_info {
+        let outer_size_px = if has_a_position {
             let size = window.outer_size();
             Some(Vec2::new(size.width as f32, size.height as f32))
         } else {

crates/egui/src/data/input.rs

@@ -75,6 +75,7 @@ pub struct RawInput {
 impl Default for RawInput {
     fn default() -> Self {
         Self {
+            viewport: ViewportInfo::default(),
             screen_rect: None,
             pixels_per_point: None,
             max_texture_side: None,
@@ -85,7 +86,6 @@ impl Default for RawInput {
             hovered_files: Default::default(),
             dropped_files: Default::default(),
             focused: true, // integrations opt into global focus tracking
-            viewport: ViewportInfo::default(),
         }
     }
 }
@@ -97,6 +97,7 @@ impl RawInput {
     /// * [`Self::dropped_files`] is moved.
     pub fn take(&mut self) -> RawInput {
         RawInput {
+            viewport: self.viewport.take(),
             screen_rect: self.screen_rect.take(),
             pixels_per_point: self.pixels_per_point.take(),
             max_texture_side: self.max_texture_side.take(),
@@ -107,13 +108,13 @@ impl RawInput {
             hovered_files: self.hovered_files.clone(),
             dropped_files: std::mem::take(&mut self.dropped_files),
             focused: self.focused,
-            viewport: self.viewport.take(),
         }
     }
 
     /// Add on new input.
     pub fn append(&mut self, newer: Self) {
         let Self {
+            viewport,
             screen_rect,
             pixels_per_point,
             max_texture_side,
@@ -124,13 +125,12 @@ impl RawInput {
             mut hovered_files,
             mut dropped_files,
             focused,
-            viewport,
         } = newer;
 
+        self.viewport = viewport;
         self.screen_rect = screen_rect.or(self.screen_rect);
         self.pixels_per_point = pixels_per_point.or(self.pixels_per_point);
         self.max_texture_side = max_texture_side.or(self.max_texture_side);
-        self.viewport = viewport;
         self.time = time; // use latest time
         self.predicted_dt = predicted_dt; // use latest dt
         self.modifiers = modifiers; // use latest

crates/egui/src/memory.rs

@@ -79,7 +79,7 @@ pub struct Memory {
     #[cfg_attr(feature = "persistence", serde(skip))]
     pub(crate) new_font_definitions: Option<epaint::text::FontDefinitions>,
 
-    // Current viewport
+    // Current active viewport
     #[cfg_attr(feature = "persistence", serde(skip))]
     pub(crate) viewport_id: ViewportId,
 
@@ -96,7 +96,6 @@ pub struct Memory {
 
     // -------------------------------------------------
     // Per-viewport:
-    #[cfg_attr(feature = "persistence", serde(skip))]
     areas: ViewportIdMap<Areas>,
 
     #[cfg_attr(feature = "persistence", serde(skip))]

crates/egui/src/viewport.rs

@@ -135,7 +135,7 @@ pub struct ViewportBuilder {
 
 impl ViewportBuilder {
     /// Default settings for the root viewport.
-    pub const ROOT: Self = Self {
+    pub const DEFAULTS: Self = Self {
         title: None,
         name: None,
         position: None,
@@ -154,18 +154,12 @@ impl ViewportBuilder {
         min_inner_size: None,
         max_inner_size: None,
         drag_and_drop: Some(true),
-        close_button: Some(false), // We disable the close button by default because we haven't implemented closing of child viewports yet
+        close_button: Some(true),
         minimize_button: Some(true),
         maximize_button: Some(true),
         hittest: Some(true),
     };
 
-    /// Default settings for a new child viewport.
-    pub const CHILD: Self = Self {
-        close_button: Some(false), // We disable the close button by default because we haven't implemented closing of child viewports yet
-        ..Self::ROOT
-    };
-
     /// Empty settings for everything.
     ///
     /// If used the first frame, backend-specific defaults will be used.

examples/multiple_viewports/src/main.rs

@@ -1,5 +1,10 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
 
+use std::sync::{
+    atomic::{AtomicBool, Ordering},
+    Arc,
+};
+
 use eframe::egui;
 
 fn main() -> Result<(), eframe::Error> {
@@ -9,7 +14,7 @@ fn main() -> Result<(), eframe::Error> {
         ..Default::default()
     };
     eframe::run_native(
-        "Confirm exit",
+        "Multiple viewports",
         options,
         Box::new(|_cc| Box::<MyApp>::default()),
     )
@@ -17,7 +22,15 @@ fn main() -> Result<(), eframe::Error> {
 
 #[derive(Default)]
 struct MyApp {
-    show_child_viewport: bool,
+    /// Immediate viewports are show immediately, so passing state to/from them is easy.
+    /// The downside is that their painting is linked with the parent viewport:
+    /// if either needs repainting, they are both repainted.
+    show_immediate_viewport: bool,
+
+    /// Deferred viewports run independant of the parent viewport, which can save
+    /// CPU if only some of the viewports require repainting.
+    /// However, this requires passing state with `Arc` and locks.
+    show_deferred_viewport: Arc<AtomicBool>,
 }
 
 impl eframe::App for MyApp {
@@ -25,17 +38,48 @@ impl eframe::App for MyApp {
         egui::CentralPanel::default().show(ctx, |ui| {
             ui.label("Hello from the root viewport");
 
-            ui.checkbox(&mut self.show_child_viewport, "Show secondary viewport");
+            ui.checkbox(
+                &mut self.show_immediate_viewport,
+                "Show immediate child viewport",
+            );
+
+            let mut show_deferred_viewport = self.show_deferred_viewport.load(Ordering::Relaxed);
+            ui.checkbox(&mut show_deferred_viewport, "Show deferred child viewport");
+            self.show_deferred_viewport
+                .store(show_deferred_viewport, Ordering::Relaxed);
         });
 
-        if self.show_child_viewport {
+        if self.show_immediate_viewport {
-            ctx.show_viewport(
+            ctx.show_viewport_immediate(
-                egui::ViewportId::from_hash_of("secondary_viewport"),
+                egui::ViewportId::from_hash_of("immediate_viewport"),
-                egui::ViewportBuilder::CHILD.with_title("Secondary Viewport"),
+                egui::ViewportBuilder::DEFAULTS.with_title("Immediate Viewport"),
                 |ctx| {
                     egui::CentralPanel::default().show(ctx, |ui| {
-                        ui.label("Hello from secondary viewport");
+                        ui.label("Hello from immediate viewport");
                     });
+                    if ctx.input(|i| i.raw.viewport.close_requested) {
+                        // Tell parent viewport that we should not show next frame:
+                        self.show_immediate_viewport = false;
+                        ctx.request_repaint(); // make sure there is a next frame
+                    }
+                },
+            );
+        }
+
+        if self.show_deferred_viewport.load(Ordering::Relaxed) {
+            let show_deferred_viewport = self.show_deferred_viewport.clone();
+            ctx.show_viewport_immediate(
+                egui::ViewportId::from_hash_of("deferred_viewport"),
+                egui::ViewportBuilder::DEFAULTS.with_title("Deferred Viewport"),
+                |ctx| {
+                    egui::CentralPanel::default().show(ctx, |ui| {
+                        ui.label("Hello from deferred viewport");
+                    });
+                    if ctx.input(|i| i.raw.viewport.close_requested) {
+                        // Tell parent to close use
+                        show_deferred_viewport.store(false, Ordering::Relaxed);
+                        ctx.request_repaint(); // make sure there is a next frame
+                    }
                 },
             );
         }

examples/test_viewports/src/main.rs

@@ -65,7 +65,7 @@ impl ViewportState {
         let immediate = vp_state.read().immediate;
         let title = vp_state.read().title.clone();
 
-        let viewport = ViewportBuilder::ROOT
+        let viewport = ViewportBuilder::DEFAULTS
             .with_title(&title)
             .with_inner_size(Some(egui::vec2(450.0, 400.0)));