Use `Task` chaining to simplify `multi_window` example

1 files changed, 72 insertions, 83 deletions

diff --git a/examples/multi_window/src/main.rs b/examples/multi_window/src/main.rs
index e15f8759..fa9adb87 100644
--- a/examples/multi_window/src/main.rs
+++ b/examples/multi_window/src/main.rs
@@ -1,16 +1,15 @@
-use iced::event;
 use iced::executor;
 use iced::multi_window::{self, Application};
 use iced::widget::{
-    button, center, column, container, scrollable, text, text_input,
+    button, center, column, container, horizontal_space, scrollable, text,
+    text_input,
 };
 use iced::window;
 use iced::{
-    Alignment, Element, Length, Point, Settings, Subscription, Task, Theme,
-    Vector,
+    Alignment, Element, Length, Settings, Subscription, Task, Theme, Vector,
 };
 
-use std::collections::HashMap;
+use std::collections::BTreeMap;
 
 fn main() -> iced::Result {
     Example::run(Settings::default())
@@ -18,8 +17,7 @@ fn main() -> iced::Result {
 
 #[derive(Default)]
 struct Example {
-    windows: HashMap<window::Id, Window>,
-    next_window_pos: window::Position,
+    windows: BTreeMap<window::Id, Window>,
 }
 
 #[derive(Debug)]
@@ -33,13 +31,12 @@ struct Window {
 
 #[derive(Debug, Clone)]
 enum Message {
+    OpenWindow,
+    WindowOpened(window::Id),
+    WindowClosed(window::Id),
     ScaleInputChanged(window::Id, String),
     ScaleChanged(window::Id, String),
     TitleChanged(window::Id, String),
-    CloseWindow(window::Id),
-    WindowOpened(window::Id, Option<Point>),
-    WindowClosed(window::Id),
-    NewWindow,
 }
 
 impl multi_window::Application for Example {
@@ -51,8 +48,7 @@ impl multi_window::Application for Example {
     fn new(_flags: ()) -> (Self, Task<Message>) {
         (
             Example {
-                windows: HashMap::from([(window::Id::MAIN, Window::new(1))]),
-                next_window_pos: window::Position::Default,
+                windows: BTreeMap::from([(window::Id::MAIN, Window::new(1))]),
             },
             Task::none(),
         )
@@ -62,79 +58,89 @@ impl multi_window::Application for Example {
         self.windows
             .get(&window)
             .map(|window| window.title.clone())
-            .unwrap_or("Example".to_string())
+            .unwrap_or_default()
     }
 
     fn update(&mut self, message: Message) -> Task<Message> {
         match message {
-            Message::ScaleInputChanged(id, scale) => {
-                let window =
-                    self.windows.get_mut(&id).expect("Window not found!");
-                window.scale_input = scale;
-
-                Task::none()
-            }
-            Message::ScaleChanged(id, scale) => {
-                let window =
-                    self.windows.get_mut(&id).expect("Window not found!");
-
-                window.current_scale = scale
-                    .parse::<f64>()
-                    .unwrap_or(window.current_scale)
-                    .clamp(0.5, 5.0);
-
-                Task::none()
+            Message::OpenWindow => {
+                let Some(last_window) = self.windows.keys().last() else {
+                    return Task::none();
+                };
+
+                window::fetch_position(*last_window)
+                    .then(|last_position| {
+                        let position = last_position.map_or(
+                            window::Position::Default,
+                            |last_position| {
+                                window::Position::Specific(
+                                    last_position + Vector::new(20.0, 20.0),
+                                )
+                            },
+                        );
+
+                        window::open(window::Settings {
+                            position,
+                            ..window::Settings::default()
+                        })
+                    })
+                    .map(Message::WindowOpened)
             }
-            Message::TitleChanged(id, title) => {
-                let window =
-                    self.windows.get_mut(&id).expect("Window not found.");
-
-                window.title = title;
+            Message::WindowOpened(id) => {
+                self.windows.insert(id, Window::new(self.windows.len() + 1));
 
-                Task::none()
+                if let Some(window) = self.windows.get(&id) {
+                    text_input::focus(window.input_id.clone())
+                } else {
+                    Task::none()
+                }
             }
-            Message::CloseWindow(id) => window::close(id),
             Message::WindowClosed(id) => {
                 self.windows.remove(&id);
+
                 Task::none()
             }
-            Message::WindowOpened(id, position) => {
-                if let Some(position) = position {
-                    self.next_window_pos = window::Position::Specific(
-                        position + Vector::new(20.0, 20.0),
-                    );
+            Message::ScaleInputChanged(id, scale) => {
+                if let Some(window) = self.windows.get_mut(&id) {
+                    window.scale_input = scale;
                 }
 
-                if let Some(window) = self.windows.get(&id) {
-                    text_input::focus(window.input_id.clone())
-                } else {
-                    Task::none()
-                }
+                Task::none()
             }
-            Message::NewWindow => {
-                let count = self.windows.len() + 1;
-
-                let (id, spawn_window) = window::open(window::Settings {
-                    position: self.next_window_pos,
-                    exit_on_close_request: count % 2 == 0,
-                    ..Default::default()
-                });
+            Message::ScaleChanged(id, scale) => {
+                if let Some(window) = self.windows.get_mut(&id) {
+                    window.current_scale = scale
+                        .parse::<f64>()
+                        .unwrap_or(window.current_scale)
+                        .clamp(0.5, 5.0);
+                }
 
-                self.windows.insert(id, Window::new(count));
+                Task::none()
+            }
+            Message::TitleChanged(id, title) => {
+                if let Some(window) = self.windows.get_mut(&id) {
+                    window.title = title;
+                }
 
-                spawn_window
+                Task::none()
             }
         }
     }
 
-    fn view(&self, window: window::Id) -> Element<Message> {
-        let content = self.windows.get(&window).unwrap().view(window);
-
-        center(content).into()
+    fn view(&self, window_id: window::Id) -> Element<Message> {
+        if let Some(window) = self.windows.get(&window_id) {
+            center(window.view(window_id)).into()
+        } else {
+            horizontal_space().into()
+        }
     }
 
-    fn theme(&self, window: window::Id) -> Self::Theme {
-        self.windows.get(&window).unwrap().theme.clone()
+    fn theme(&self, window: window::Id) -> Theme {
+        if let Some(window) = self.windows.get(&window) {
+            window.theme.clone()
+        } else {
+            Theme::default()
+        }
     }
 
     fn scale_factor(&self, window: window::Id) -> f64 {
@@ -145,24 +151,7 @@ impl multi_window::Application for Example {
     }
 
     fn subscription(&self) -> Subscription<Self::Message> {
-        event::listen_with(|event, _, window| {
-            if let iced::Event::Window(window_event) = event {
-                match window_event {
-                    window::Event::CloseRequested => {
-                        Some(Message::CloseWindow(window))
-                    }
-                    window::Event::Opened { position, .. } => {
-                        Some(Message::WindowOpened(window, position))
-                    }
-                    window::Event::Closed => {
-                        Some(Message::WindowClosed(window))
-                    }
-                    _ => None,
-                }
-            } else {
-                None
-            }
-        })
+        window::closings().map(Message::WindowClosed)
     }
 }
 
@@ -200,7 +189,7 @@ impl Window {
         ];
 
         let new_window_button =
-            button(text("New Window")).on_press(Message::NewWindow);
+            button(text("New Window")).on_press(Message::OpenWindow);
 
         let content = scrollable(
             column![scale_input, title_input, new_window_button]