use refineable::Refineable as _; use crate::{    App, Bounds, Element, ElementId, GlobalElementId, IntoElement, Pixels, Style, StyleRefinement,    Styled, Window,}; /// Construct a canvas element with the given paint callback./// Useful for adding short term custom drawing to a view.pub fn canvas<T>(    prepaint: impl 'static + FnOnce(Bounds<Pixels>, &mut Window, &mut App) -> T,    paint: impl 'static + FnOnce(Bounds<Pixels>, T, &mut Window, &mut App),) -> Canvas<T> {    Canvas {        prepaint: Some(Box::new(prepaint)),        paint: Some(Box::new(paint)),        style: StyleRefinement::default(),    }} /// A canvas element, meant for accessing the low level paint API without defining a whole/// custom elementpub struct Canvas<T> {    prepaint: Option<Box<dyn FnOnce(Bounds<Pixels>, &mut Window, &mut App) -> T>>,    paint: Option<Box<dyn FnOnce(Bounds<Pixels>, T, &mut Window, &mut App)>>,    style: StyleRefinement,} impl<T: 'static> IntoElement for Canvas<T> {    type Element = Self;     fn into_element(self) -> Self::Element {        self    }} impl<T: 'static> Element for Canvas<T> {    type RequestLayoutState = Style;    type PrepaintState = Option<T>;     fn id(&self) -> Option<ElementId> {        None    }     fn request_layout(        &mut self,        _id: Option<&GlobalElementId>,        window: &mut Window,        cx: &mut App,    ) -> (crate::LayoutId, Self::RequestLayoutState) {        let mut style = Style::default();        style.refine(&self.style);        let layout_id = window.request_layout(style.clone(), [], cx);        (layout_id, style)    }     fn prepaint(        &mut self,        _id: Option<&GlobalElementId>,        bounds: Bounds<Pixels>,        _request_layout: &mut Style,        window: &mut Window,        cx: &mut App,    ) -> Option<T> {        Some(self.prepaint.take().unwrap()(bounds, window, cx))    }     fn paint(        &mut self,        _id: Option<&GlobalElementId>,        bounds: Bounds<Pixels>,        style: &mut Style,        prepaint: &mut Self::PrepaintState,        window: &mut Window,        cx: &mut App,    ) {        let prepaint = prepaint.take().unwrap();        style.paint(bounds, window, cx, |window, cx| {            (self.paint.take().unwrap())(bounds, prepaint, window, cx)        });    }} impl<T> Styled for Canvas<T> {    fn style(&mut self) -> &mut crate::StyleRefinement {        &mut self.style    }}