/*

File: BitHolder.h

Abstract: Protocol for a layer that acts as a container for Bits.

Version: 1.0

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*/

#import <Quartz/Quartz.h>

@class Bit;

/** Protocol for a layer that acts as a container for Bits. */

@protocol BitHolder <NSObject>

/** Current Bit, or nil if empty */

@property (retain) Bit* bit;

/** Conveniences for comparing self.bit with nil */

@property (readonly, getter=isEmpty) BOOL empty;

/** BitHolders will be highlighted while the target of a drag operation */

@property BOOL highlighted;

/** Tests whether the bit is allowed to be dragged out of me.

    Returns the input bit, or possibly a different Bit to drag instead, or nil if not allowed.

    Either -cancelDragBit: or -draggedBit:to: must be called next. */

- (Bit*) canDragBit: (Bit*)bit;

/** Cancels a pending drag (begun by -canDragBit:). */

- (void) cancelDragBit: (Bit*)bit;

/** Called after a drag finishes. */

- (void) draggedBit: (Bit*)bit to: (id<BitHolder>)dst;

/** Tests whether the bit is allowed to be dropped into me.

    Either -willNotDropBit: or -dropBit:atPoint: must be called next. */

- (BOOL) canDropBit: (Bit*)bit atPoint: (CGPoint)point;

/** Cancels a pending drop (after -canDropBit:atPoint: was already called.) */

- (void) willNotDropBit: (Bit*)bit;

/** Finishes a drop. */

- (BOOL) dropBit: (Bit*)bit atPoint: (CGPoint)point;

@end

/** A basic implementation of the BitHolder protocol. */

@interface BitHolder : CALayer <BitHolder>

{

    @protected

    Bit *_bit;

    BOOL _highlighted;

}

@end