first good start

src/main.rs

@@ -1,3 +1,96 @@
-fn main() {
-    println!("Hello, world!");
+use iced::mouse;
+use iced::widget::canvas;
+use iced::widget::canvas::Stroke;
+use iced::widget::canvas::Style;
+use iced::widget::{button, column, row, text};
+use iced::{Color, Rectangle, Renderer, Theme};
+
+fn main() -> iced::Result {
+    iced::run("My App", MyApp::update, MyApp::view)
+}
+
+#[derive(Debug, Clone)]
+enum Message {
+    ButtonPressedIncrement,
+    ButtonPressedDecrement,
+}
+
+#[derive(Default)]
+struct MyApp {
+    counter: f32,
+}
+
+impl MyApp {
+    fn update(&mut self, message: Message) {
+        match message {
+            Message::ButtonPressedIncrement => self.counter += 32.0,
+            Message::ButtonPressedDecrement => {
+                if self.counter > 0.0 {
+                    self.counter -= 32.0
+                }
+            }
+        }
+    }
+
+    fn view(&self) -> iced::Element<Message> {
+        column![
+            text(self.counter),
+            row![
+                button("Increment").on_press(Message::ButtonPressedIncrement),
+                button("Decrement").on_press(Message::ButtonPressedDecrement),
+            ],
+            canvas(Circle {
+                radius: self.counter
+            })
+            .height(500)
+            .width(500),
+        ]
+        .into()
+    }
+}
+
+struct Circle {
+    radius: f32,
+}
+
+impl<Message> canvas::Program<Message> for Circle {
+    // No internal state
+    type State = ();
+
+    fn draw(
+        &self,
+        _state: &(),
+        renderer: &Renderer,
+        _theme: &Theme,
+        bounds: Rectangle,
+        _cursor: mouse::Cursor,
+    ) -> Vec<canvas::Geometry> {
+        // We prepare a new `Frame`
+        //println!("w:{}, h:{}", bounds.size().width, bounds.size().height);
+        let mut frame = canvas::Frame::new(renderer, bounds.size());
+
+        // We create a `Path` representing a simple circle
+        let circle = canvas::Path::circle(frame.center(), self.radius);
+        let line = canvas::Path::line(frame.center(), iced::Point { x: 0.0, y: 0.0 });
+        frame.stroke(
+            &line,
+            Stroke {
+                width: 5.0,
+                ..Stroke::default()
+            },
+        );
+
+        // And fill it with some color
+        frame.stroke(
+            &circle,
+            Stroke {
+                width: 5.0,
+                style: Style::Solid(Color::from_rgba(0.0, 0.0, 0.0, 1.0)),
+                ..Stroke::default()
+            },
+        );
+
+        // Then, we produce the geometry
+        vec![frame.into_geometry()]
+    }
 }