ebiten/internal/packing/packing.go
2024-01-13 17:42:51 +09:00

351 lines
8.5 KiB
Go

// Copyright 2018 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package packing offers a packing algorithm in 2D space.
package packing
import (
"errors"
"fmt"
"image"
)
type Page struct {
root *Node
width int
height int
maxSize int
}
func isPositivePowerOf2(x int) bool {
if x <= 0 {
return false
}
for x > 1 {
if x/2*2 != x {
return false
}
x /= 2
}
return true
}
func NewPage(initWidth, initHeight int, maxSize int) *Page {
if !isPositivePowerOf2(initWidth) {
panic(fmt.Sprintf("packing: initWidth must be a positive power of 2 but %d", initWidth))
}
if !isPositivePowerOf2(initHeight) {
panic(fmt.Sprintf("packing: initHeight must be a positive power of 2 but %d", initHeight))
}
if !isPositivePowerOf2(maxSize) {
panic(fmt.Sprintf("packing: maxSize must be a positive power of 2 but %d", maxSize))
}
return &Page{
width: initWidth,
height: initHeight,
maxSize: maxSize,
}
}
func (p *Page) IsEmpty() bool {
if p.root == nil {
return true
}
return !p.root.used && p.root.child0 == nil && p.root.child1 == nil
}
type Node struct {
region image.Rectangle
used bool
parent *Node
child0 *Node
child1 *Node
}
func (n *Node) canFree() bool {
if n.used {
return false
}
if n.child0 == nil && n.child1 == nil {
return true
}
return n.child0.canFree() && n.child1.canFree()
}
func (n *Node) Region() image.Rectangle {
return n.region
}
// square returns a float value indicating how much the given rectangle is close to a square.
// If the given rectangle is square, this return 1 (maximum value).
// Otherwise, this returns a value in [0, 1).
func square(width, height int) float64 {
if width == 0 && height == 0 {
return 0
}
if width <= height {
return float64(width) / float64(height)
}
return float64(height) / float64(width)
}
func alloc(n *Node, width, height int) *Node {
if n.region.Dx() < width || n.region.Dy() < height {
return nil
}
if n.used {
return nil
}
if n.child0 == nil && n.child1 == nil {
if n.region.Dx() == width && n.region.Dy() == height {
n.used = true
return n
}
if square(n.region.Dx()-width, n.region.Dy()) >= square(n.region.Dx(), n.region.Dy()-height) {
// Split vertically
n.child0 = &Node{
region: image.Rect(n.region.Min.X, n.region.Min.Y, n.region.Min.X+width, n.region.Max.Y),
parent: n,
}
n.child1 = &Node{
region: image.Rect(n.region.Min.X+width, n.region.Min.Y, n.region.Max.X, n.region.Max.Y),
parent: n,
}
} else {
// Split horizontally
n.child0 = &Node{
region: image.Rect(n.region.Min.X, n.region.Min.Y, n.region.Max.X, n.region.Min.Y+height),
parent: n,
}
n.child1 = &Node{
region: image.Rect(n.region.Min.X, n.region.Min.Y+height, n.region.Max.X, n.region.Max.Y),
parent: n,
}
}
// Note: it now MUST fit, due to above preconditions (repeated here).
if n.child0.region.Dx() < width || n.child0.region.Dy() < height {
panic(fmt.Sprintf("packing: the newly created child node (%d, %d) unexpectedly does not contain the requested size (%d, %d)", n.child0.region.Dx(), n.child0.region.Dy(), width, height))
}
// Thus, alloc can't return nil, but it may do another split along the other dimension
// to get a node with the exact size (width, height).
node := alloc(n.child0, width, height)
if node == nil {
panic(fmt.Sprintf("packing: could not allocate the requested size (%d, %d) in the newly created child node (%d, %d)", width, height, n.child0.region.Dx(), n.child0.region.Dy()))
}
return node
}
if n.child0 == nil || n.child1 == nil {
panic("packing: both two children must not be nil at alloc")
}
if node := alloc(n.child0, width, height); node != nil {
return node
}
if node := alloc(n.child1, width, height); node != nil {
return node
}
return nil
}
func (p *Page) Size() (int, int) {
return p.width, p.height
}
func (p *Page) Alloc(width, height int) *Node {
if width <= 0 || height <= 0 {
panic("packing: width and height must > 0")
}
if p.root == nil {
p.root = &Node{
region: image.Rect(0, 0, p.width, p.height),
}
}
return p.extendAndAlloc(width, height)
}
func (p *Page) Free(node *Node) {
if node.child0 != nil || node.child1 != nil {
panic("packing: can't free the node including children")
}
node.used = false
if node.parent == nil {
return
}
if node.parent.child0 == nil || node.parent.child1 == nil {
panic("packing: both two children must not be nil at Free: double free happened?")
}
if node.parent.child0.canFree() && node.parent.child1.canFree() {
node.parent.child0 = nil
node.parent.child1 = nil
p.Free(node.parent)
}
}
func walk(n *Node, f func(n *Node) error) error {
if err := f(n); err != nil {
return err
}
if n.child0 != nil {
if err := walk(n.child0, f); err != nil {
return err
}
}
if n.child1 != nil {
if err := walk(n.child1, f); err != nil {
return err
}
}
return nil
}
func (p *Page) extendAndAlloc(width, height int) *Node {
if n := alloc(p.root, width, height); n != nil {
return n
}
if p.width >= p.maxSize && p.height >= p.maxSize {
return nil
}
// (1, 0), (0, 1), (2, 0), (1, 1), (0, 2), (3, 0), (2, 1), (1, 2), (0, 3), ...
for i := 1; ; i++ {
for j := 0; j <= i; j++ {
newWidth := p.width
for k := 0; k < i-j; k++ {
newWidth *= 2
}
newHeight := p.height
for k := 0; k < j; k++ {
newHeight *= 2
}
if newWidth > p.maxSize || newHeight > p.maxSize {
if newWidth > p.maxSize && newHeight > p.maxSize {
panic(fmt.Sprintf("packing: too big extension: allocating size: (%d, %d), current size: (%d, %d), new size: (%d, %d), (i, j): (%d, %d), max size: %d", width, height, p.width, p.height, newWidth, newHeight, i, j, p.maxSize))
}
continue
}
rollback := p.extend(newWidth, newHeight)
if n := alloc(p.root, width, height); n != nil {
return n
}
rollback()
// If the allocation failed even with a maximized page, give up the allocation.
if newWidth >= p.maxSize && newHeight >= p.maxSize {
return nil
}
}
}
}
func (p *Page) extend(newWidth int, newHeight int) func() {
edgeNodes := []*Node{}
abort := errors.New("abort")
aborted := false
if p.root != nil {
_ = walk(p.root, func(n *Node) error {
if n.region.Max.X < p.width && n.region.Max.Y < p.height {
return nil
}
if n.used {
aborted = true
return abort
}
edgeNodes = append(edgeNodes, n)
return nil
})
}
var rollback func()
if aborted {
origRoot := p.root
origRootCloned := *p.root
// Extend the page in the vertical direction.
if newHeight-p.height > 0 {
upper := p.root
lower := &Node{
region: image.Rect(0, p.height, p.width, newHeight),
}
p.root = &Node{
region: image.Rect(0, 0, p.width, newHeight),
child0: upper,
child1: lower,
}
upper.parent = p.root
lower.parent = p.root
}
// Extend the page in the horizontal direction.
if newWidth-p.width > 0 {
left := p.root
right := &Node{
region: image.Rect(p.width, 0, newWidth, newHeight),
}
p.root = &Node{
region: image.Rect(0, 0, newWidth, newHeight),
child0: left,
child1: right,
}
left.parent = p.root
right.parent = p.root
}
origWidth, origHeight := p.width, p.height
rollback = func() {
p.width = origWidth
p.height = origHeight
// The node address must not be changed, so use the original root node's pointer (#2584).
// As the root node might be modified, restore the content by the cloned content.
p.root = origRoot
*p.root = origRootCloned
}
} else {
origWidth, origHeight := p.width, p.height
origMaxXs := map[*Node]int{}
origMaxYs := map[*Node]int{}
for _, n := range edgeNodes {
if n.region.Max.X == p.width {
origMaxXs[n] = n.region.Max.X
n.region.Max.X = newWidth
}
if n.region.Max.Y == p.height {
origMaxYs[n] = n.region.Max.Y
n.region.Max.Y = newHeight
}
}
rollback = func() {
p.width = origWidth
p.height = origHeight
for n, x := range origMaxXs {
n.region.Max.X = x
}
for n, y := range origMaxYs {
n.region.Max.Y = y
}
}
}
p.width = newWidth
p.height = newHeight
return rollback
}