1use refineable::Refineable as _;
 2
 3use crate::{Bounds, Element, ElementContext, IntoElement, Pixels, Style, StyleRefinement, Styled};
 4
 5/// Construct a canvas element with the given paint callback.
 6/// Useful for adding short term custom drawing to a view.
 7pub fn canvas(callback: impl 'static + FnOnce(&Bounds<Pixels>, &mut ElementContext)) -> Canvas {
 8    Canvas {
 9        paint_callback: Some(Box::new(callback)),
10        style: StyleRefinement::default(),
11    }
12}
13
14/// A canvas element, meant for accessing the low level paint API without defining a whole
15/// custom element
16pub struct Canvas {
17    paint_callback: Option<Box<dyn FnOnce(&Bounds<Pixels>, &mut ElementContext)>>,
18    style: StyleRefinement,
19}
20
21impl IntoElement for Canvas {
22    type Element = Self;
23
24    fn element_id(&self) -> Option<crate::ElementId> {
25        None
26    }
27
28    fn into_element(self) -> Self::Element {
29        self
30    }
31}
32
33impl Element for Canvas {
34    type State = Style;
35
36    fn request_layout(
37        &mut self,
38        _: Option<Self::State>,
39        cx: &mut ElementContext,
40    ) -> (crate::LayoutId, Self::State) {
41        let mut style = Style::default();
42        style.refine(&self.style);
43        let layout_id = cx.request_layout(&style, []);
44        (layout_id, style)
45    }
46
47    fn paint(&mut self, bounds: Bounds<Pixels>, style: &mut Style, cx: &mut ElementContext) {
48        style.paint(bounds, cx, |cx| {
49            (self.paint_callback.take().unwrap())(&bounds, cx)
50        });
51    }
52}
53
54impl Styled for Canvas {
55    fn style(&mut self) -> &mut crate::StyleRefinement {
56        &mut self.style
57    }
58}