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/// A connection to the state of a shell.
///
/// A [`Widget`] can leverage a [`Shell`] to trigger changes in an application,
/// like publishing messages or invalidating the current layout.
///
/// [`Widget`]: crate::Widget
#[derive(Debug)]
pub struct Shell<'a, Message> {
messages: &'a mut Vec<Message>,
is_layout_invalid: bool,
are_widgets_invalid: bool,
}
impl<'a, Message> Shell<'a, Message> {
/// Creates a new [`Shell`] with the provided buffer of messages.
pub fn new(messages: &'a mut Vec<Message>) -> Self {
Self {
messages,
is_layout_invalid: false,
are_widgets_invalid: false,
}
}
/// Triggers the given function if the layout is invalid, cleaning it in the
/// process.
pub fn revalidate_layout(&mut self, f: impl FnOnce()) {
if self.is_layout_invalid {
self.is_layout_invalid = false;
f()
}
}
/// Publish the given `Message` for an application to process it.
pub fn publish(&mut self, message: Message) {
self.messages.push(message);
}
/// Invalidates the current application layout.
///
/// The shell will relayout the application widgets.
pub fn invalidate_layout(&mut self) {
self.is_layout_invalid = true;
}
/// Invalidates the current application widgets.
///
/// The shell will rebuild and relayout the widget tree.
pub fn invalidate_widgets(&mut self) {
self.are_widgets_invalid = true;
}
/// Merges the current [`Shell`] with another one by applying the given
/// function to the messages of the latter.
///
/// This method is useful for composition.
pub fn merge<B>(&mut self, other: Shell<'_, B>, f: impl Fn(B) -> Message) {
self.messages.extend(other.messages.drain(..).map(f));
self.is_layout_invalid =
self.is_layout_invalid || other.is_layout_invalid;
self.are_widgets_invalid =
self.are_widgets_invalid || other.are_widgets_invalid;
}
/// Returns whether the widgets of the current application have been
/// invalidated.
pub fn are_widgets_invalid(&self) -> bool {
self.are_widgets_invalid
}
}
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