Canvas

Canvas calls a painter with PaintContext& and the component’s measured Size. Its local drawing rectangle is {0, 0, size.width, size.height}.

Canvas([](PaintContext& paint, Size size) {
  const Point center{size.width * 0.5F, size.height * 0.5F};
  paint.DrawCircle(center, 48.0F, Color::Rgb(92, 72, 180));
  paint.DrawCircle(center, 24.0F, Color::White());
}).With(Frame{.width = 160.0F, .height = 160.0F})

Painting

PaintContext records immutable platform-neutral commands for rectangles, gradients, text, images, external textures, circles, arcs, borders, shadows, paths, clipping, and transforms. Platform renderers replay the resulting PaintSequence.

Balance every pushed clip or transform on all painter paths. Prefer local coordinates derived from the supplied Size; parent placement is applied later by the render scene.

Updating a canvas

Capture declarative values in the painter. When a captured State read changes, recomposition supplies a new painter and invalidates the canvas paint result. For continuous visual motion, apply retained animation modifiers such as Rotation(AnimateTo(...)) rather than updating state every display frame.

Accessibility and input

Canvas has no inferred semantic meaning. Add Semantics for charts, controls, or other meaningful drawings, and bind pointer events only when the custom content is interactive.

Canvas(DrawChart)
    .With(Semantics{
        .role = SemanticRole::Image,
        .label = "Revenue by quarter",
    })

API

• Constructor: Canvas(CanvasPainter) where CanvasPainter is std::function<void(PaintContext&, Size)>.
• Common modifiers: Frame, Grow, ClipChildren, transforms, Semantics.

Read Canvas, paint, path, and vector for the full drawing surface.