#ifndef	_DISPLAY_H
#define	_DISPLAY_H	1

//---
//	Types and constants.
//---

enum Color
{
	Color_White	= 0,	// White	(AND 0)
	Color_Black	= 1,	// Black	(OR 1)
	Color_None	= 2,	// Transparent	(NOP)
	Color_Invert	= 3,	// Invert	(XOR 1)
};

/*
	enum BlendingMode
	Describes the various blending modes available for drawing images.
	Blending modes may be combined for special effects! For instance:
	- Or		Only sets black pixels.
	- And		Only erases white pixels.
	- Or | And	Fully draws the bitmap.
	- Invert	Inverts pixels where the bitmap is black.
	- Or | Invert	Erases black pixels.
	Adding Checker to an existing combination limits the operation to
	pixels (x, y) that satisfy (x + y) & 1 == 1.
	Operations are done in the following order : Or - Invert - And.
*/
enum BlendingMode
{
	Blend_Or	= 0x01,
	Blend_Invert	= 0x02,
	Blend_And	= 0x04,

	Blend_Checker	= 0x10,
};

enum ImageFormat
{
	ImageFormat_Mono	= 0x01,
	ImageFormat_Gray	= 0x02,

	ImageFormat_Alpha	= 0x10,

	ImageFormat_ColorMask	= 0x0f,
};

struct Image
{
	unsigned char width;
	unsigned char height;
	unsigned char format;

	// Ensures data is 4-aligned.
	unsigned char gap;

	const unsigned char __attribute__((aligned(4))) data[];

} __attribute__((aligned(4)));

typedef struct Image Image;



#define	DISPLAY_WIDTH	128
#define	DISPLAY_HEIGHT	64



//---
//	Generic functions.
//---

/*
	display_getLocalVRAM()
	Returns the local video ram. This address should not be used directly
	when running the gray engine.

	@return	Video ram address of the monochrome display module.
*/
void *display_getLocalVRAM(void);

/*
	display_useVRAM()
	Changes the current video ram address. Expects a *4-aligned* 1024-byte
	buffer.
	Do not use this function while running the gray engine.

	@arg	New video ram address.
*/
void display_useVRAM(void *vram);



//---
//	Global drawing functions.
//---

/*
	dupdate()
	Displays the vram on the physical screen.
*/
void dupdate(void);

/*
	dclear()
	Clears the whole video ram.
*/
void dclear(void);

/*
	dclear_area()
	Clears an area of the video ram.

	@arg	x1
	@arg	y1
	@arg	x2
	@arg	y2
*/
void dclear_area(int x1, int y1, int x2, int y2);

/*
	dreverse_area()
	Reverses an area of the screen.

	@arg	x1
	@arg	y1
	@arg	x2
	@arg	y2
*/
void dreverse_area(int x1, int y1, int x2, int y2);



//---
//	Local drawing functions.
//---

/*
	dpixel()
	Puts a pixel on the screen.

	@arg	x
	@arg	y
	@arg	color
*/
void dpixel(int x, int y, enum Color color);

/*
	dline()
	Draws a line on the screen. Automatically optimizes horizontal and
	vertical lines.

	Uses an algorithm written by PierrotLL for MonochromeLib.

	@arg	x1
	@arg	y1
	@arg	x2
	@arg	y2
	@arg	color
*/
void dline(int x1, int y1, int x2, int y2, enum Color color);



//---
//	Image drawing.
//---

/*
	dimage()
	Displays an image in the vram.

	@arg	image
	@arg	x
	@arg	y
	@arg	mode
*/
void dimage(struct Image *image, int x, int y, enum BlendingMode mode);

#endif	// _DISPLAY_H