ebiten/internal/restorable/images.go

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// Copyright 2017 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 restorable
import (
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"github.com/hajimehoshi/ebiten/internal/sync"
)
type images struct {
images map[*Image]struct{}
lastChecked *Image
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m sync.Mutex
}
var theImages = &images{
images: map[*Image]struct{}{},
}
func ResolveStalePixels() error {
return theImages.resolveStalePixels()
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}
func Restore() error {
return theImages.restore()
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}
func ClearVolatileImages() {
theImages.clearVolatileImages()
}
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func (i *images) add(img *Image) {
i.m.Lock()
defer i.m.Unlock()
i.images[img] = struct{}{}
}
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func (i *images) remove(img *Image) {
i.m.Lock()
defer i.m.Unlock()
delete(i.images, img)
}
func (i *images) resolveStalePixels() error {
i.m.Lock()
defer i.m.Unlock()
i.lastChecked = nil
for img := range i.images {
if err := img.resolveStalePixels(); err != nil {
return err
}
}
return nil
}
func (i *images) resetPixelsIfDependingOn(target *Image) {
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// Avoid defer for performance
i.m.Lock()
if target == nil {
// disposed
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i.m.Unlock()
return
}
if i.lastChecked == target {
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i.m.Unlock()
return
}
i.lastChecked = target
for img := range i.images {
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// TODO: This seems not enough: What if img becomes stale but what about
// other images depend on img? (#357)
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img.makeStaleIfDependingOn(target)
}
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i.m.Unlock()
}
func (i *images) restore() error {
i.m.Lock()
defer i.m.Unlock()
// Framebuffers/textures cannot be disposed since framebuffers/textures that
// don't belong to the current context.
// Let's do topological sort based on dependencies of drawing history.
// There should not be a loop since cyclic drawing makes images stale.
type edge struct {
source *Image
target *Image
}
images := map[*Image]struct{}{}
for i := range i.images {
images[i] = struct{}{}
}
edges := map[edge]struct{}{}
for t := range images {
for s := range t.dependingImages() {
edges[edge{source: s, target: t}] = struct{}{}
}
}
sorted := []*Image{}
for len(images) > 0 {
// current repesents images that have no incoming edges.
current := map[*Image]struct{}{}
for i := range images {
current[i] = struct{}{}
}
for e := range edges {
if _, ok := current[e.target]; ok {
delete(current, e.target)
}
}
for i := range current {
delete(images, i)
sorted = append(sorted, i)
}
removed := []edge{}
for e := range edges {
if _, ok := current[e.source]; ok {
removed = append(removed, e)
}
}
for _, e := range removed {
delete(edges, e)
}
}
for _, img := range sorted {
if err := img.restore(); err != nil {
return err
}
}
return nil
}
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func (i *images) clearVolatileImages() {
i.m.Lock()
defer i.m.Unlock()
for img := range i.images {
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img.clearIfVolatile()
}
}