32 lines
1.1 KiB
Go
32 lines
1.1 KiB
Go
package gohan
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import (
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"errors"
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"github.com/hajimehoshi/ebiten/v2"
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)
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// System represents a system that runs continuously.
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//
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// Systems may specify any number of required components by adding public
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// fields to their struct. When no required components are specified, the
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// system will run for every active entity.
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//
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// While systems must implement the Update and Draw methods, the special error
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// value ErrUnregister may be returned at any time by systems to indicate the
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// method returning the error should not be called again.
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//
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// Systems do not need to implement locking to prevent race conditions between
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// Update and Draw methods. Ebitengine calls only one of these methods at a time.
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type System interface {
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// Update is called once for each matching Entity each time the game state is updated.
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Update(e Entity) error
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// Draw is called once for each matching Entity each time the game is drawn to the screen.
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Draw(e Entity, screen *ebiten.Image) error
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}
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// ErrUnregister is a special error value which may be used to unregister a
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// system from Draw or Update events.
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var ErrUnregister = errors.New("unregister system")
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