Struct CanvasWidget 

pub struct CanvasWidget { /* private fields */ }

Declarative custom painting over the [PaintScene] trait object — a chart, a node-and-edge graph, a game board — without hand-rolling a View/ Widget pair. canvas takes a paint closure that runs in local space (the widget’s own top-left is always (0, 0), and painting past its own size is clipped, never a bug to chase) — flat-re-exported from frust-widgets so app code never names that crate directly. See CanvasView’s own doc for the full builder contract (.size/.expand sizing, .on_hit-gated .on_tap/.on_pointer, and .repaint_key for paint-only dirtying driven by data outside the ordinary View diff).

use frust::authoring::{PaintCtx, PaintScene};
use frust::{AnyView, Component, any, canvas};
use kurbo::{Point, Size};
use peniko::Color;

#[derive(Default)]
struct Clock;

impl Component for Clock {
    type State = u32;

    fn init(&self) -> Self::State {
        0
    }

    fn build(&self, state: &mut Self::State) -> AnyView<Self::State> {
        let ticks = *state;
        any(canvas(move |scene: &mut dyn PaintScene, size: Size, _ctx: &PaintCtx| {
            scene.fill_rect(Point::ZERO, size, Color::from_rgb8(0x10, 0x10, 0x10));
        })
        .expand()
        .repaint_key(ticks))
    }
}

frust::app!(Clock);

The retained widget for a CanvasView. See the module docs.

Trait Implementations

impl Widget for CanvasWidget

fn layout(&mut self, _ctx: &mut LayoutCtx<'_>, bc: &BoxConstraints) -> Size

Choose a size within bc and return it. The chosen size must satisfy bc (callers may additionally clamp via BoxConstraints::constrain).

fn paint(&mut self, ctx: &mut PaintCtx<'_>, scene: &mut dyn PaintScene)

Emit draw commands for this widget into scene.

fn event(&mut self, ctx: &mut EventCtx<'_>, event: &InputEvent) -> EventResult

Handle an input event, optionally mutating application state through ctx and reporting whether it was consumed.

fn semantics(&self, _ctx: &mut SemanticsCtx)

Contribute this widget’s accessibility node(s) into ctx.

fn type_name(&self) -> &'static str

This widget’s concrete type name, for read-only tooling.

fn visit_children(&self, _visitor: &mut dyn FnMut(&ChildPod))

Visit this widget’s owned ChildPods, in declaration (paint) order — the read-only seam that makes the retained hierarchy enumerable.