93 lines
1.9 KiB
Go
93 lines
1.9 KiB
Go
package engine
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import (
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"encoding/gob"
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"math"
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"sort"
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"github.com/hajimehoshi/ebiten/v2"
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)
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// Ensure Scene satisfies Scener.
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var _ Scener = &Scene{}
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func init() {
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gob.Register(Scene{})
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}
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// Scene manages drawing and updating a bunch of components.
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type Scene struct {
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ID
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Bounds // world coordinates
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Components []interface{}
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Disabled
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Hidden
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ZOrder
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}
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// Draw draws all components in order.
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func (s *Scene) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
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if s.Hidden {
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return
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}
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// Draw everything.
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for _, i := range s.Components {
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if d, ok := i.(Drawer); ok {
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d.Draw(screen, opts)
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}
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}
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}
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// Prepare does an initial Z-order sort.
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func (s *Scene) Prepare(game *Game) { s.sortByDrawOrder() }
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// sortByDrawOrder sorts the components by Z position.
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// Everything without a Z sorts first. Stable sort is used to avoid Z-fighting
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// (among layers without a Z, or those with equal Z).
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func (s *Scene) sortByDrawOrder() {
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sort.SliceStable(s.Components, func(i, j int) bool {
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a, aok := s.Components[i].(DrawOrderer)
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b, bok := s.Components[j].(DrawOrderer)
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if aok && bok {
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return a.DrawOrder() < b.DrawOrder()
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}
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return !aok && bok
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})
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}
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// Scan returns all immediate subcomponents.
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func (s *Scene) Scan() []interface{} { return s.Components }
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// Scene returns itself.
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func (s *Scene) Scene() *Scene { return s }
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// Update calls Update on all Updater components.
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func (s *Scene) Update() error {
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if s.Disabled {
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return nil
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}
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for _, c := range s.Components {
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// Update each updater in turn
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if u, ok := c.(Updater); ok {
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if err := u.Update(); err != nil {
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return err
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}
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}
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}
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// Check if the updates put the components out of order; if so, sort
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cz := -math.MaxFloat64 // fun fact: this is min float64
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for _, c := range s.Components {
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z, ok := c.(DrawOrderer)
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if !ok {
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continue
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}
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if t := z.DrawOrder(); t > cz {
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cz = t
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continue
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}
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s.sortByDrawOrder()
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return nil
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}
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return nil
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}
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