ui: add carousel loading spinner

gui/ui/src/component/mod.rs

@@ -8,6 +8,7 @@ pub mod form;
 pub mod hw;
 pub mod modal;
 pub mod notification;
+pub mod spinner;
 pub mod text;
 pub mod toast;
 pub mod tooltip;

gui/ui/src/component/spinner.rs

@@ -0,0 +1,157 @@
+use std::time::Duration;
+
+use iced::{
+    advanced::{
+        layout, renderer,
+        widget::tree::{self, Tree},
+        Clipboard, Layout, Shell, Widget,
+    },
+    event, mouse,
+    time::Instant,
+    window, Element, Event, Length, Rectangle, Renderer, Size,
+};
+
+/// A loading spinner widget that cycles through a collection of
+/// `children` at a fixed rate.
+///
+/// `interval` is how long to wait before displaying the next child.
+pub struct Carousel<'a, Message, Theme> {
+    interval: Duration,
+    children: Vec<Element<'a, Message, Theme>>,
+}
+
+impl<'a, Message, Theme> Carousel<'a, Message, Theme> {
+    pub fn new(interval: Duration, children: Vec<impl Into<Element<'a, Message, Theme>>>) -> Self {
+        Carousel {
+            interval,
+            children: children.into_iter().map(|child| child.into()).collect(),
+        }
+    }
+}
+
+/// The state of a `Carousel`.
+///
+/// `last_transition` is when the `current`th child
+/// of `Carousel::children` was selected.
+struct CarouselState {
+    last_transition: Instant,
+    current: usize,
+}
+
+impl CarouselState {
+    fn new() -> Self {
+        Self {
+            last_transition: Instant::now(),
+            current: 0,
+        }
+    }
+}
+
+impl<'a, Message, Theme> Widget<Message, Theme, Renderer> for Carousel<'a, Message, Theme>
+where
+    Message: 'a + Clone,
+{
+    fn tag(&self) -> tree::Tag {
+        tree::Tag::of::<CarouselState>()
+    }
+
+    fn diff(&self, tree: &mut Tree) {
+        tree.diff_children(self.children.as_slice());
+    }
+
+    fn layout(
+        &self,
+        tree: &mut Tree,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let state = tree.state.downcast_mut::<CarouselState>();
+        let child_nodes: Vec<_> = self
+            .children
+            .iter()
+            .enumerate()
+            .map(|(i, child)| {
+                child
+                    .as_widget()
+                    .layout(&mut tree.children[i], renderer, limits)
+            })
+            .collect();
+        layout::Node::with_children(child_nodes[state.current].size(), child_nodes)
+    }
+
+    fn children(&self) -> Vec<Tree> {
+        self.children.iter().map(|child| Tree::new(child)).collect()
+    }
+
+    fn state(&self) -> tree::State {
+        tree::State::new(CarouselState::new())
+    }
+
+    fn size(&self) -> Size<Length> {
+        // Use an arbitrary size here as the layout node size
+        // is determined from the current child.
+        Size {
+            width: Length::Shrink,
+            height: Length::Shrink,
+        }
+    }
+
+    fn on_event(
+        &mut self,
+        tree: &mut Tree,
+        event: Event,
+        _layout: Layout<'_>,
+        _cursor: mouse::Cursor,
+        _renderer: &Renderer,
+        _clipboard: &mut dyn Clipboard,
+        shell: &mut Shell<'_, Message>,
+        _viewport: &Rectangle,
+    ) -> event::Status {
+        let state = tree.state.downcast_mut::<CarouselState>();
+        if let Event::Window(_, window::Event::RedrawRequested(now)) = event {
+            if now.duration_since(state.last_transition) > self.interval {
+                state.last_transition = now;
+                state.current = (state.current + 1) % self.children.len();
+            }
+            shell.request_redraw(window::RedrawRequest::NextFrame);
+        }
+        event::Status::Ignored
+    }
+
+    fn draw(
+        &self,
+        tree: &Tree,
+        renderer: &mut Renderer,
+        theme: &Theme,
+        style: &renderer::Style,
+        layout: Layout<'_>,
+        cursor: mouse::Cursor,
+        viewport: &Rectangle,
+    ) {
+        let state = tree.state.downcast_ref::<CarouselState>();
+        let current = self.children.get(state.current).expect("current");
+        let current_layout = layout
+            .children()
+            .nth(state.current)
+            .expect("current layout");
+        current.as_widget().draw(
+            &tree.children[state.current],
+            renderer,
+            theme,
+            style,
+            current_layout,
+            cursor,
+            viewport,
+        );
+    }
+}
+
+impl<'a, Message, Theme> From<Carousel<'a, Message, Theme>> for Element<'a, Message, Theme>
+where
+    Message: 'a + Clone,
+    Theme: 'a,
+{
+    fn from(carousel: Carousel<'a, Message, Theme>) -> Self {
+        Element::new(carousel)
+    }
+}