Initializer

init(opaque:colorMode:rendersAsynchronously:renderer:)

Creates and configures a canvas.

Declaration 宣言 

init(opaque: Bool = false, colorMode: ColorRenderingMode = .nonLinear, rendersAsynchronously: Bool = false, renderer: @escaping (inout GraphicsContext, CGSize) -> Void)
Available when Symbols is EmptyView.

Parameters パラメータ

opaque

A Boolean that indicates whether the canvas is fully opaque. You might be able to improve performance by setting this value to true, but then drawing a non-opaque image into the context produces undefined results. The default is false.

colorMode

A working color space and storage format of the canvas. The default is ColorRenderingMode.nonLinear.

rendersAsynchronously

A Boolean that indicates whether the canvas can present its contents to its parent view asynchronously. The default is false.

renderer

A closure in which you conduct immediate mode drawing. The closure takes two inputs: a context that you use to issue drawing commands and a size — representing the current size of the canvas — that you can use to customize the content. The canvas calls the renderer any time it needs to redraw the content.

Discussion 議論

Use this initializer to create a new canvas that you can draw into. For example, you can draw a path:


Canvas { context, size in
    context.stroke(
        Path(ellipseIn: CGRect(origin: .zero, size: size)),
        with: .color(.green),
        lineWidth: 4)
}
.frame(width: 300, height: 200)
.border(Color.blue)

The example above draws the outline of an ellipse that exactly inscribes a canvas with a blue border:

A screenshot of a canvas view that shows the green outline of an

For information about using a context to draw into a canvas, see GraphicsContext. If you want to provide SwiftUI views for the renderer to use as drawing elements, use init(opaque:colorMode:rendersAsynchronously:renderer:symbols:) instead.

See Also 参照

Creating a Canvas

init(opaque: Bool, colorMode: ColorRenderingMode, rendersAsynchronously: Bool, renderer: (inout GraphicsContext, CGSize) -> Void, symbols: () -> Symbols)
Creates and configures a canvas that you supply with renderable child views.