ichigo/engine/game.go

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package engine
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import (
"encoding/gob"
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"errors"
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"fmt"
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"image"
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"io/fs"
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"log"
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"reflect"
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"sort"
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"sync"
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"time"
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"drjosh.dev/gurgle/geom"
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"github.com/hajimehoshi/ebiten/v2"
)
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var _ interface {
Disabler
Hider
Identifier
Updater
Scanner
} = &Game{}
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var (
errNilComponent = errors.New("nil component")
errNilParent = errors.New("nil parent")
)
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func init() {
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gob.Register(&Game{})
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}
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// Game implements the ebiten methods using a collection of components. One
// component must be the designated root component - usually a scene of some
// kind.
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type Game struct {
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Disabled
Hidden
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ScreenSize image.Point
Root interface{} // typically a *Scene or SceneRef though
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Projection geom.IntProjection
VoxelScale geom.Float3
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dbmu sync.RWMutex
byID map[string]Identifier // Named components by ID
byAB map[abKey]map[interface{}]struct{} // Ancestor/behaviour index
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drawList drawList // draw list :|
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par map[interface{}]interface{} // par[x] is parent of x
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}
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// Draw draws everything.
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func (g *Game) Draw(screen *ebiten.Image) {
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if g.Hidden {
return
}
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// Hiding a parent component should hide the child objects, and the
// transform applied to a child should be the cumulative transform of all
// parents as well.
// accum memoises the results for each component.
type state struct {
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hidden bool
opts ebiten.DrawImageOptions
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}
accum := map[interface{}]state{
g: {hidden: false},
}
// Draw everything in g.drawList, where not hidden (itself or any parent)
for _, d := range g.drawList {
// Is d hidden itself?
if h, ok := d.(Hider); ok && h.IsHidden() {
accum[d] = state{hidden: true}
continue // skip drawing
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}
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// Walk up g.par to find the nearest state in accum.
var st state
stack := []interface{}{d}
for p := g.par[d]; ; p = g.par[p] {
if s, found := accum[p]; found {
st = s
break
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}
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stack = append(stack, p)
}
// Unwind the stack, accumulating state along the way.
for len(stack) > 0 {
l1 := len(stack) - 1
p := stack[l1]
stack = stack[:l1]
if h, ok := p.(Hider); ok {
st.hidden = st.hidden || h.IsHidden()
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}
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if st.hidden {
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accum[p] = state{hidden: true}
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continue
}
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// p is not hidden, so compute its cumulative opts.
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if tf, ok := p.(Transformer); ok {
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st.opts = ConcatOpts(tf.Transform(), st.opts)
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}
accum[p] = st
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}
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// Skip drawing if hidden.
if st.hidden {
continue
}
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d.Draw(screen, &st.opts)
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}
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}
// Layout returns the configured screen width/height.
func (g *Game) Layout(outsideWidth, outsideHeight int) (w, h int) {
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return g.ScreenSize.X, g.ScreenSize.Y
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}
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// Update updates everything.
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func (g *Game) Update() error {
if g.Disabled {
return nil
}
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// Need to do a similar trick for Draw: disabling a parent object should
// disable the child objects.
// accum memoises the disabled state for each component.
accum := map[interface{}]bool{
g: false,
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}
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// Update everything that is not disabled.
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// TODO: do it in a fixed order? map essentially randomises iteration order
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for u := range g.Query(g.Ident(), UpdaterType) {
// Skip g (note g satisfies Updater, so this would infinitely recurse)
if u == g {
continue
}
// Is u disabled itself?
if d, ok := u.(Disabler); ok && d.IsDisabled() {
accum[u] = true
continue
}
// Walk up g.par to find the nearest state in accum.
var st bool
stack := []interface{}{u}
for p := g.par[u]; ; p = g.par[p] {
if s, found := accum[p]; found {
st = s
break
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}
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stack = append(stack, p)
}
// Unwind the stack, accumulating state along the way.
for len(stack) > 0 {
l1 := len(stack) - 1
p := stack[l1]
stack = stack[:l1]
if d, ok := p.(Disabler); ok {
st = st || d.IsDisabled()
}
accum[p] = st
}
// Skip updating if disabled.
if st {
continue
}
if err := u.(Updater).Update(); err != nil {
return err
}
}
// Sort the draw list (on every frame - this isn't as bad as it sounds)
sort.Stable(g.drawList)
// Truncate tombstones from the end.
for i := len(g.drawList) - 1; i >= 0; i-- {
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if g.drawList[i] == (Tombstone{}) {
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g.drawList = g.drawList[:i]
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}
}
return nil
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}
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// Ident returns "__GAME__".
func (g *Game) Ident() string { return "__GAME__" }
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// Component returns the component with a given ID, or nil if there is none.
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// This only returns sensible values for registered components (e.g. after
// LoadAndPrepare).
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func (g *Game) Component(id string) Identifier {
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g.dbmu.RLock()
defer g.dbmu.RUnlock()
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return g.byID[id]
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}
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// Parent returns the parent of a given component, or nil if there is none.
// This only returns sensible values for registered components (e.g. after
// LoadAndPrepare).
func (g *Game) Parent(c interface{}) interface{} {
g.dbmu.RLock()
defer g.dbmu.RUnlock()
return g.par[c]
}
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// Query looks for components having both a given ancestor and implementing
// a given behaviour (see Behaviors in interface.go). This only returns sensible
// values after LoadAndPrepare. Note that every component is its own ancestor.
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func (g *Game) Query(ancestorID string, behaviour reflect.Type) map[interface{}]struct{} {
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g.dbmu.RLock()
defer g.dbmu.RUnlock()
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return g.byAB[abKey{ancestorID, behaviour}]
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}
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// Scan implements Scanner.
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func (g *Game) Scan() []interface{} { return []interface{}{g.Root} }
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// PreorderWalk calls visit with every component and its parent, reachable from
// the given component via Scan, for as long as visit returns nil. The parent
// value passed to visit when visiting component will be nil. The parent will be
// visited before the children.
func PreorderWalk(component interface{}, visit func(component, parent interface{}) error) error {
return preorderWalk(component, nil, visit)
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}
func preorderWalk(component, parent interface{}, visit func(component, parent interface{}) error) error {
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if err := visit(component, parent); err != nil {
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return err
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}
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sc, ok := component.(Scanner)
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if !ok {
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return nil
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}
for _, c := range sc.Scan() {
if err := preorderWalk(c, component, visit); err != nil {
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return err
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}
}
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return nil
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}
// PostorderWalk calls visit with every component and its parent, reachable from
// the given component via Scan, for as long as visit returns nil. The parent
// value passed to visit when visiting component will be nil. The children will
// be visited before the parent.
func PostorderWalk(component interface{}, visit func(component, parent interface{}) error) error {
return preorderWalk(component, nil, visit)
}
func postorderWalk(component, parent interface{}, visit func(component, parent interface{}) error) error {
if sc, ok := component.(Scanner); ok {
for _, c := range sc.Scan() {
if err := postorderWalk(c, component, visit); err != nil {
return err
}
}
}
return visit(component, parent)
}
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// LoadAndPrepare first calls Load on all Loaders. Once loading is complete, it
// builds the component databases and then calls Prepare on every Preparer.
// LoadAndPrepare must be called before any calls to Component or Query.
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func (g *Game) LoadAndPrepare(assets fs.FS) error {
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if g.VoxelScale == (geom.Float3{}) {
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g.VoxelScale = geom.Float3{X: 1, Y: 1, Z: 1}
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}
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// Load all the Loaders.
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startLoad := time.Now()
if err := PreorderWalk(g, func(c, _ interface{}) error {
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l, ok := c.(Loader)
if !ok {
return nil
}
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return l.Load(assets)
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}); err != nil {
return err
}
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log.Printf("finished loading in %v", time.Since(startLoad))
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// Build the component databases
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startBuild := time.Now()
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g.dbmu.Lock()
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g.byID = make(map[string]Identifier)
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g.byAB = make(map[abKey]map[interface{}]struct{})
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g.par = make(map[interface{}]interface{})
if err := PreorderWalk(g, g.register); err != nil {
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return err
}
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g.dbmu.Unlock()
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log.Printf("finished building db in %v", time.Since(startBuild))
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// Prepare all the Preppers
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startPrep := time.Now()
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for p := range g.Query(g.Ident(), PrepperType) {
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if err := p.(Prepper).Prepare(g); err != nil {
return err
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}
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}
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log.Printf("finished preparing in %v", time.Since(startPrep))
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return nil
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}
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// Register registers a component into the component database (as the
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// child of a given parent). Passing a nil component or parent is an error.
// Registering multiple components with the same ID is also an error.
// Registering a component will recursively register all children found via
// Scan.
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func (g *Game) Register(component, parent interface{}) error {
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if component == nil {
return errNilComponent
}
if parent == nil && component != g {
return errNilParent
}
g.dbmu.Lock()
defer g.dbmu.Unlock()
// walk goes in the right order for registering.
return preorderWalk(component, parent, g.register)
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}
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func (g *Game) register(component, parent interface{}) error {
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// register in g.byID if needed. nothing else errors so do this first
if i, ok := component.(Identifier); ok {
id := i.Ident()
if _, exists := g.byID[id]; exists {
return fmt.Errorf("duplicate id %q", id)
}
g.byID[id] = i
}
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// register in g.par
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if parent != nil {
g.par[component] = parent
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}
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// register in g.drawList
if d, ok := component.(Drawer); ok {
g.drawList = append(g.drawList, d)
}
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// register in g.byAB
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ct := reflect.TypeOf(component)
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for _, b := range Behaviours {
if !ct.Implements(b) {
continue
}
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// TODO: better than O(len(path)^2) time and memory?
for p := component; p != nil; p = g.par[p] {
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i, ok := p.(Identifier)
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if !ok {
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continue
}
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k := abKey{i.Ident(), b}
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if g.byAB[k] == nil {
g.byAB[k] = make(map[interface{}]struct{})
}
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g.byAB[k][component] = struct{}{}
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}
}
return nil
}
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// Unregister removes the component from the component database.
// Passing a nil component has no effect. Unregistering a component will
// recursively unregister child components found via Scan.
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func (g *Game) Unregister(component interface{}) {
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if component == nil {
return
}
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g.dbmu.Lock()
postorderWalk(component, nil, func(c, _ interface{}) error {
g.unregister(c)
return nil
})
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g.dbmu.Unlock()
}
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func (g *Game) unregister(component interface{}) {
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// unregister from g.byAB, using g.par to trace the path
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ct := reflect.TypeOf(component)
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for _, b := range Behaviours {
if !ct.Implements(b) {
continue
}
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for p := component; p != nil; p = g.par[p] {
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i, ok := p.(Identifier)
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if !ok {
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continue
}
k := abKey{i.Ident(), b}
if g.byAB[k] == nil {
continue
}
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delete(g.byAB[k], component)
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}
}
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// unregister from g.par
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delete(g.par, component)
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// unregister from g.drawList
for i, d := range g.drawList {
if d == component {
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g.drawList[i] = Tombstone{}
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}
}
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// unregister from g.byID if needed
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if i, ok := component.(Identifier); ok {
delete(g.byID, i.Ident())
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}
}
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// --------- Helper stuff ---------
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type abKey struct {
ancestor string
behaviour reflect.Type
}
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var _ Drawer = Tombstone{}
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type Tombstone struct{}
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func (Tombstone) Draw(*ebiten.Image, *ebiten.DrawImageOptions) {}
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func (Tombstone) DrawAfter(x Drawer) bool {
return x != Tombstone{}
}
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type drawList []Drawer
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func (d drawList) Less(i, j int) bool { return d[j].DrawAfter(d[i]) }
func (d drawList) Len() int { return len(d) }
func (d drawList) Swap(i, j int) { d[i], d[j] = d[j], d[i] }
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// ConcatOpts returns the combined options (as though a was applied and then b).
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func ConcatOpts(a, b ebiten.DrawImageOptions) ebiten.DrawImageOptions {
a.ColorM.Concat(b.ColorM)
a.GeoM.Concat(b.GeoM)
if b.CompositeMode != 0 {
a.CompositeMode = b.CompositeMode
}
if b.Filter != 0 {
a.Filter = b.Filter
}
return a
}