Canvas

Paints rectangles and vector paths from a list of commands. The commands travel in the snapshot and run entirely in Rust, so no Go callback runs during painting.

chart := scene.Canvas(1,
	&scene.DrawCommand{Kind: &scene.DrawCommandRect{Rect: &scene.DrawRect{
		Bounds: &scene.Bounds{
			Origin: &scene.Point{X: 10, Y: 10},
			Size:   &scene.Size{Width: 130, Height: 70},
		},
		Fill:   scene.RGB(0x2563eb),
		Radius: 8,
	}}},
	&scene.DrawCommand{Kind: &scene.DrawCommandPath{Path: &scene.DrawPath{
		Color:       scene.RGB(0x34d399),
		StrokeWidth: 4,
		Steps: []*scene.PathStep{
			{Verb: scene.PathMove, Point: &scene.Point{X: 10, Y: 100}},
			{Verb: scene.PathLine, Point: &scene.Point{X: 140, Y: 100}},
		},
	}}},
).Style(&scene.Style{
	Width:  scene.Pixels(160),
	Height: scene.Pixels(120),
})

Signature

func Canvas(id uint64, commands ...*DrawCommand) *Node

Coordinates are logical pixels relative to the element's top-left corner, and drawing is clipped to the element. The canvas fills its box, so set Width and Height. Commands paint in order, later ones on top. A canvas cannot have children.

Rectangle

scene.DrawCommandRect wraps a scene.DrawRect:

Field	Type	Description
Bounds	*scene.Bounds	Required Origin and Size. Width and height cannot be negative
Fill	*scene.Color	Fill color. Transparent if nil
Border	*scene.Color	Border color. Transparent if nil
BorderWidth	float32	Border width, at least 0
Radius	float32	Corner radius, at least 0

Path

scene.DrawCommandPath wraps a scene.DrawPath:

Field	Type	Description
Steps	[]*scene.PathStep	Required. The first step must be scene.PathMove
Color	*scene.Color	Paint color. Transparent if nil
StrokeWidth	float32	0 fills the path. A larger value strokes it at that width

Each scene.PathStep has a Verb and the points it requires:

Verb	Required fields	Effect
scene.PathMove	Point	Starts a new subpath at Point
scene.PathLine	Point	Draws a straight line to Point
scene.PathQuadratic	Point, Control1	Draws a quadratic curve to Point
scene.PathCubic	Point, Control1, Control2	Draws a cubic curve to Point
scene.PathClose	None	Closes the subpath

Limits

Limit	Value
Commands per canvas	4096
Path steps per canvas, across all paths	16,384
Coordinate and size magnitude	1,000,000
Color channels	0 to 1, finite

Available in other APIs

Canvas is only available through scene.