ichigo/engine/walls.go

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Go
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package engine
import (
"image"
"github.com/hajimehoshi/ebiten/v2"
)
var (
_ interface {
Collider
Identifier
Scanner
} = &Wall{}
_ interface {
Drawer
Disabler
Hider
Prepper
} = &WallUnit{}
)
// Wall is a more flexible kind of tilemap. WallUnits can be added at the same
// level as other components and are responsible for their own drawing, so that
// Scene can do draw ordering, e.g. hide the player character behind a wall.
// But Wall is still responsible for collisions.
type Wall struct {
ID
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Ersatz bool // disables collisions ("fake wall")
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Offset image.Point // offset the whole wall
Sheet Sheet
UnitOffset image.Point // drawing offset
UnitSize image.Point // tile size
units map[image.Point]*WallUnit
}
func (w *Wall) regUnit(u *WallUnit) {
if w.units == nil {
w.units = make(map[image.Point]*WallUnit)
}
w.units[u.Pos] = u
}
func (w *Wall) CollidesWith(r image.Rectangle) bool {
if w.Ersatz {
return false
}
// Probe the map at all tilespace coordinates overlapping the rect.
r = r.Sub(w.Offset)
min := div2(r.Min, w.UnitSize)
max := div2(r.Max.Sub(image.Pt(1, 1)), w.UnitSize) // NB: fencepost
for j := min.Y; j <= max.Y; j++ {
for i := min.X; i <= max.X; i++ {
if w.units[image.Pt(i, j)] != nil {
return true
}
}
}
return false
}
func (w *Wall) Scan() []interface{} { return []interface{}{&w.Sheet} }
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// WallUnit is a unit in a wall. Unlike a tile in a tilemap, WallUnit is
// responsible for drawing itself.
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type WallUnit struct {
Disabled
Hidden
Pos image.Point // tilespace coordinates
Tile Tile // chooses which cell in wall.Sheet to draw
WallID string
ZOrder
wall *Wall
}
func (u *WallUnit) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
var geom ebiten.GeoM
geom.Translate(float2(mul2(u.Pos, u.wall.UnitSize).Add(u.wall.UnitOffset).Add(u.wall.Offset)))
geom.Concat(opts.GeoM)
opts.GeoM = geom
src := u.wall.Sheet.SubImage(u.Tile.CellIndex())
screen.DrawImage(src, &opts)
}
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func (u *WallUnit) Prepare(g *Game) error {
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u.wall = g.Component(u.WallID).(*Wall)
u.wall.regUnit(u)
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return nil
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}
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func (u *WallUnit) Scan() []interface{} { return []interface{}{u.Tile} }