//////////////////////////////////////////////////////////////////////////////
//
//  This file is part of the Atari Machine Specific Library,
//  and is Copyright 1992 by Warwick W. Allison.
//
//  You are free to copy and modify these sources, provided you acknoledge
//  the origin by retaining this notice, and adhere to the conditions
//  described in the file COPYING.
//
//////////////////////////////////////////////////////////////////////////////

#ifndef _DoubleBuffer_h
#define _DoubleBuffer_h
//
//  Encapsulated Double Buffering support.
//
//  Various other modules in this library write to the current double
//  buffer page.  Double buffering provides smoothe output, even at
//  slow update rates.
//
//  To use, simply create two Screens you want to use as the two pages,
//  and create Pages with them.  eg. Pages=new DoubleBuffer(This,That);
//
//  Once created, use Pages->Flip() to swap pages.  This call includes
//  a wait for vertical retrace.
//
//  Too write on the double buffer (as Sprites do), write to the screen
//  specified by Pages->Current(), or just access Pages->Location().
//
//  Use Flop() if, for some reason, you don't want the retrace to be
//  waited for.
//
//  NowShowing() gives the page PHYSICALLY showing, whereas Location() is
//  the page not showing.  For double buffering to work correctly, you
//  should never write on the currently shown page.
//

#include "screen.h"

class DoubleBuffer
{
public:
	DoubleBuffer();
	DoubleBuffer(Screen&,Screen&);

	void	Flip();	// Swap pages smoothly (synced to retrace)
	void	Flop();	// Swap pages immediately (unsynced)
	char 	*Location();
	char 	*NowShowing();
	Screen&	Current();

	short Pulse;

private:
	Screen* Canvas[2];
};

extern	DoubleBuffer *Pages;


inline char *DoubleBuffer::Location() { return Canvas[Pulse]->Location(); }
inline char *DoubleBuffer::NowShowing() { return Canvas[1-Pulse]->Location(); }
inline Screen&	DoubleBuffer::Current() { return *Canvas[Pulse]; }

#endif