ichigo/engine/anim.go

70 lines
1.3 KiB
Go

package engine
import "encoding/gob"
// Ensure Anim satisfies Animer.
var _ Animer = &Anim{}
func init() {
gob.Register(&Anim{})
}
// AnimFrame describes a frame in an animation.
type AnimFrame struct {
Frame int // show this frame
Duration int // for this long, in ticks
}
// Anim is n animation being displayed, together with the current state.
// A nil *Anim can be used, but always returns 0 for the current frame.
type Anim struct {
Frames []AnimFrame
OneShot bool
Index int
Ticks int
}
// Copy makes a shallow copy of the anim.
func (a *Anim) Copy() *Anim {
if a == nil {
return nil
}
a2 := *a
return &a2
}
// CurrentFrame returns the frame number for the current index.
func (a *Anim) CurrentFrame() int {
if a == nil {
return 0
}
return a.Frames[a.Index].Frame
}
// Reset resets both Index and Ticks to 0.
func (a *Anim) Reset() {
if a == nil {
return
}
a.Index, a.Ticks = 0, 0
}
// Update increments the tick count and advances the frame if necessary.
func (a *Anim) Update() error {
if a == nil {
return nil
}
a.Ticks++
if a.OneShot && a.Index == len(a.Frames)-1 {
// on the last frame of a one shot so remain on final frame
return nil
}
if a.Ticks >= a.Frames[a.Index].Duration {
a.Ticks = 0
a.Index++
}
if !a.OneShot && a.Index >= len(a.Frames) {
a.Index = 0
}
return nil
}