doodle/doodads/actor.go

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package doodads
import (
"git.kirsle.net/apps/doodle/level"
"git.kirsle.net/apps/doodle/render"
)
// Actor is a reusable run-time drawing component used in Doodle. Actors are an
// active instance of a Doodad which have a position, velocity, etc.
type Actor interface {
ID() string
// Position and velocity, not saved to disk.
Position() render.Point
Velocity() render.Point
Size() render.Rect
Grounded() bool
SetGrounded(bool)
// Movement commands.
MoveBy(render.Point) // Add {X,Y} to current Position.
MoveTo(render.Point) // Set current Position to {X,Y}.
// Implement the Draw function.
Draw(render.Engine)
}
// GetBoundingRect computes the full pairs of points for the collision box
// around a doodad actor.
func GetBoundingRect(d Actor) render.Rect {
var (
P = d.Position()
S = d.Size()
)
return render.Rect{
X: P.X,
Y: P.Y,
W: S.W,
H: S.H,
}
}
// ScanBoundingBox scans all of the pixels in a bounding box on the grid and
// returns if any of them intersect with level geometry.
func (c *Collide) ScanBoundingBox(box render.Rect, grid *level.Chunker) bool {
col := GetCollisionBox(box)
c.ScanGridLine(col.Top[0], col.Top[1], grid, Top)
c.ScanGridLine(col.Bottom[0], col.Bottom[1], grid, Bottom)
c.ScanGridLine(col.Left[0], col.Left[1], grid, Left)
c.ScanGridLine(col.Right[0], col.Right[1], grid, Right)
return c.IsColliding()
}
// ScanGridLine scans all of the pixels between p1 and p2 on the grid and tests
// for any pixels to be set, implying a collision between level geometry and the
// bounding boxes of the doodad.
func (c *Collide) ScanGridLine(p1, p2 render.Point, grid *level.Chunker, side Side) {
for point := range render.IterLine2(p1, p2) {
if _, err := grid.Get(point); err == nil {
// A hit!
switch side {
case Top:
c.Top = true
c.TopPoint = point
case Bottom:
c.Bottom = true
c.BottomPoint = point
case Left:
c.Left = true
c.LeftPoint = point
case Right:
c.Right = true
c.RightPoint = point
}
}
}
}