71 lines
1.7 KiB
Go
71 lines
1.7 KiB
Go
package engine
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import "github.com/hajimehoshi/ebiten/v2"
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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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func (tombstone) DrawBefore(Drawer) bool { return false }
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type drawList struct {
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list []Drawer
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rev map[Drawer]int
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}
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func (d drawList) Less(i, j int) bool {
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// Deal with tombstones first, in case anything else thinks it
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// needs to go last.
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if d.list[i] == (tombstone{}) {
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return false
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}
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if d.list[j] == (tombstone{}) {
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return true
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}
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// Common logic for known interfaces (BoundingBoxer, ZPositioner), to
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// simplify Draw{Before,After} implementations.
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switch x := d.list[i].(type) {
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case BoundingBoxer:
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xb := x.BoundingBox()
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switch y := d.list[j].(type) {
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case BoundingBoxer:
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yb := y.BoundingBox()
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if xb.Min.Z >= yb.Max.Z { // x is in front of y
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return false
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}
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if xb.Max.Z <= yb.Min.Z { // x is behind y
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return true
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}
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if xb.Max.Y <= yb.Min.Y { // x is above y
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return false
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}
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if xb.Min.Y >= yb.Max.Y { // x is below y
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return true
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}
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case ZPositioner:
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return xb.Max.Z < y.ZPos() // x is before y
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}
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case ZPositioner:
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switch y := d.list[j].(type) {
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case BoundingBoxer:
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return x.ZPos() < y.BoundingBox().Min.Z
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case ZPositioner:
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return x.ZPos() < y.ZPos()
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}
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}
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// Fallback case: ask the components themselves
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return d.list[i].DrawBefore(d.list[j]) || d.list[j].DrawAfter(d.list[i])
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}
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func (d drawList) Len() int { return len(d.list) }
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func (d drawList) Swap(i, j int) {
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d.rev[d.list[i]], d.rev[d.list[j]] = j, i
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d.list[i], d.list[j] = d.list[j], d.list[i]
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}
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