sprite

Documentation

Overview

Package sprite provides a 2D scene graph for rendering and animation.

A tree of nodes is drawn by a rendering Engine, provided by another package. The OS-independent Go version based on the image package is:

golang.org/x/mobile/exp/sprite/portable

An Engine draws a screen starting at a root Node. The tree is walked depth-first, with affine transformations applied at each level.

Nodes are rendered relative to their parent.

Typical main loop:

for each frame {
	quantize time.Now() to a clock.Time
	process UI events
	modify the scene's nodes and animations (Arranger values)
	e.Render(scene, t, sz)
}

Index

• type Arranger
• type Engine
• type Node
  • func (n *Node) AppendChild(c *Node)
  • func (n *Node) RemoveChild(c *Node)
• type SubTex
• type Texture

Types

type Arranger

type Arranger interface {
	Arrange(e Engine, n *Node, t clock.Time)
}

type Engine

type Engine interface {
	Register(n *Node)
	Unregister(n *Node)

	LoadTexture(a image.Image) (Texture, error)

	SetSubTex(n *Node, x SubTex)
	SetTransform(n *Node, m f32.Affine) // sets transform relative to parent.

	// Render renders the scene arranged at the given time, for the given
	// window configuration (dimensions and resolution).
	Render(scene *Node, t clock.Time, sz size.Event)
}

type Node

type Node struct {
	Parent, FirstChild, LastChild, PrevSibling, NextSibling *Node

	Arranger Arranger

	// EngineFields contains fields that should only be accessed by Engine
	// implementations. It is exported because such implementations can be
	// in other packages.
	EngineFields struct {
		// TODO: separate TexDirty and TransformDirty bits?
		Dirty  bool
		Index  int32
		SubTex SubTex
	}
}

A Node is a renderable element and forms a tree of Nodes.

func (*Node) AppendChild

func (n *Node) AppendChild(c *Node)

AppendChild adds a node c as a child of n.

It will panic if c already has a parent or siblings.

func (*Node) RemoveChild

func (n *Node) RemoveChild(c *Node)

RemoveChild removes a node c that is a child of n. Afterwards, c will have no parent and no siblings.

It will panic if c's parent is not n.

type SubTex

type SubTex struct {
	T Texture
	R image.Rectangle
}

type Texture

type Texture interface {
	Bounds() (w, h int)
	Download(r image.Rectangle, dst draw.Image)
	Upload(r image.Rectangle, src image.Image)
	Unload()
}