Adding upstream version 0.0~git20250520.a1d9079+dfsg.

Signed-off-by: Daniel Baumann <daniel@debian.org>

exp/sprite/sprite.go

@@ -0,0 +1,126 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// 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)
+//	}
+package sprite
+
+import (
+	"image"
+	"image/draw"
+
+	"golang.org/x/mobile/event/size"
+	"golang.org/x/mobile/exp/f32"
+	"golang.org/x/mobile/exp/sprite/clock"
+)
+
+type Arranger interface {
+	Arrange(e Engine, n *Node, t clock.Time)
+}
+
+type Texture interface {
+	Bounds() (w, h int)
+	Download(r image.Rectangle, dst draw.Image)
+	Upload(r image.Rectangle, src image.Image)
+	Release()
+}
+
+type SubTex struct {
+	T Texture
+	R image.Rectangle
+}
+
+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)
+
+	Release()
+}
+
+// A Node is a renderable element and forms a tree of Nodes.
+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
+	}
+}
+
+// AppendChild adds a node c as a child of n.
+//
+// It will panic if c already has a parent or siblings.
+func (n *Node) AppendChild(c *Node) {
+	if c.Parent != nil || c.PrevSibling != nil || c.NextSibling != nil {
+		panic("sprite: AppendChild called for an attached child Node")
+	}
+	last := n.LastChild
+	if last != nil {
+		last.NextSibling = c
+	} else {
+		n.FirstChild = c
+	}
+	n.LastChild = c
+	c.Parent = n
+	c.PrevSibling = last
+}
+
+// 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.
+func (n *Node) RemoveChild(c *Node) {
+	if c.Parent != n {
+		panic("sprite: RemoveChild called for a non-child Node")
+	}
+	if n.FirstChild == c {
+		n.FirstChild = c.NextSibling
+	}
+	if c.NextSibling != nil {
+		c.NextSibling.PrevSibling = c.PrevSibling
+	}
+	if n.LastChild == c {
+		n.LastChild = c.PrevSibling
+	}
+	if c.PrevSibling != nil {
+		c.PrevSibling.NextSibling = c.NextSibling
+	}
+	c.Parent = nil
+	c.PrevSibling = nil
+	c.NextSibling = nil
+}