/*
	For more information, please see:
	- http://cgfm2.emuviews.com/txt/msvdp.txt
	- http://www.smspower.org/forums/viewtopic.php?p=44198

A scanline contains the following sections:
  - horizontal sync     1  ED      => HSYNC high/increment line counter/generate interrupts/etc
  - left blanking       2  ED-EE
  - color burst        14  EE-EF
  - left blanking       8  F5-F9
  - left border        13  F9-FF
  - active display    256  00-7F
  - right border       15  80-87
  - right blanking      8  87-8B
  - horizontal sync    25  8B-97   => HSYNC low


NTSC frame timing
                       256x192         256x224        256x240 (doesn't work on real hardware)
  - vertical blanking   3  D5-D7        3  E5-E7       3  EE-F0
  - top blanking       13  D8-E4       13  E8-F4      13  F1-FD
  - top border         27  E5-FF       11  F5-FF       3  FD-FF
  - active display    192  00-BF      224  00-DF     240  00-EF
  - bottom border      24  C0-D7        8  E0-E7       0  F0-F0
  - bottom blanking     3  D8-DA        3  E8-EA       3  F0-F2


PAL frame timing
                       256x192         256x224        256x240
  - vertical blanking   3  BA-BC        3  CA-CC       3  D2-D4
  - top blanking       13  BD-C9       13  CD-D9      13  D5-E1
  - top border         54  CA-FF       38  DA-FF      30  E2-FF
  - active display    192  00-BF      224  00-DF     240  00-EF
  - bottom border      48  C0-EF       32  E0-FF      24  F0-07
  - bottom blanking     3  F0-F2        3  00-02       3  08-0A

*/

#include "driver.h"
#include "video/smsvdp.h"
#include "includes/sms.h"
#include "video/generic.h"
#include "cpu/z80/z80.h"

#define IS_SMS1_VDP		( features & MODEL_315_5124 )
#define IS_SMS2_VDP		( features & MODEL_315_5246 )
#define IS_GAMEGEAR_VDP		( features & MODEL_315_5378 )

#define STATUS_VINT		(0x80)	/* Pending vertical interrupt flag */
#define STATUS_SPROVR		(0x40)	/* Sprite overflow flag */
#define STATUS_SPRCOL		(0x20)	/* Object collision flag */
#define STATUS_HINT		(0x02)	/* Pending horizontal interrupt flag */

#define GG_CRAM_SIZE		(0x40)	/* 32 colors x 2 bytes per color = 64 bytes */
#define SMS_CRAM_SIZE		(0x20)	/* 32 colors x 1 bytes per color = 32 bytes */
#define MAX_CRAM_SIZE		0x40

#define VRAM_SIZE		(0x4000)

#define PRIORITY_BIT		0x1000
#define BACKDROP_COLOR		( ( vdp_mode == 4 ? 0x10 : 0x00 ) + (reg[0x07] & 0x0F))

#define NUM_OF_REGISTER		(0x10)  /* 16 registers */

#define INIT_VCOUNT		0
#define VERTICAL_BLANKING	1
#define TOP_BLANKING		2
#define TOP_BORDER		3
#define ACTIVE_DISPLAY_V	4
#define BOTTOM_BORDER		5
#define BOTTOM_BLANKING		6

static UINT8 sms_ntsc_192[7] = { 0xD5, 3, 13, 27, 192, 24, 3 };
static UINT8 sms_ntsc_224[7] = { 0xE5, 3, 13, 11, 224,  8, 3 };
static UINT8 sms_ntsc_240[7] = { 0xEE, 3, 13,  3, 240,  0, 3 };
static UINT8 sms_pal_192[7]  = { 0xBA, 3, 13, 54, 192, 48, 3 };
static UINT8 sms_pal_224[7]  = { 0xCA, 3, 13, 38, 224, 32, 3 };
static UINT8 sms_pal_240[7]  = { 0xD2, 3, 13, 30, 240, 24, 3 };

UINT8 *sms_frame_timing;

UINT8 reg[NUM_OF_REGISTER];
UINT8 *VRAM = NULL;
UINT8 *CRAM = NULL;
int CRAMMask;
UINT8 *lineCollisionBuffer;
UINT8 reg9copy;

int addr;
int code;
int pending;
int latch;
int buffer;
int statusReg;
int ggSmsMode;
UINT32 features;

int isCRAMDirty;

int lineCountDownCounter;
int irqState;			/* The status of the IRQ line, as seen by the VDP */
int y_pixels;			/* 192, 224, 240 */
int vdp_mode;			/* current mode of the VDP: 0,1,2,3,4 */

mame_bitmap *prevBitMap;

/* lineBuffer will be used to hold 5 lines of line data. Line #0 is the regular blitting area.
   Lines #1-#4 will be used as a kind of cache to be used for vertical scaling in the gamegear
   sms compatibility mode.
 */
int *lineBuffer = NULL;
int currentPalette[32];
int prevBitMapSaved;
void (*int_callback)(int);
mame_timer *smsvdp_display_timer = NULL;

static TIMER_CALLBACK(smsvdp_display_callback);
void sms_refresh_line(mame_bitmap *bitmap, int offsetx, int offsety, int line);
void sms_update_palette(void);

static void set_display_settings( void ) {
	int M1, M2, M3, M4;
	M1 = reg[0x01] & 0x10;
	M2 = reg[0x00] & 0x02;
	M3 = reg[0x01] & 0x08;
	M4 = reg[0x00] & 0x04;
	y_pixels = 192;
	if ( M4 ) {
		/* mode 4 */
		vdp_mode = 4;
		if ( M2 && ( IS_SMS2_VDP || IS_GAMEGEAR_VDP ) ) {
			/* Is it 224-line display */
			if ( M1 && ! M3 ) {
				y_pixels = 224;
			} else if ( ! M1 && M3 ) {
				/* 240-line display */
				y_pixels = 240;
			}
		}
	} else {
		/* original TMS9918 mode */
		if ( ! M1 && ! M2 && ! M3 ) {
			vdp_mode = 0;
		} else
//		if ( M1 && ! M2 && ! M3 ) {
//			vdp_mode = 1;
//		} else
		if ( ! M1 && M2 && ! M3 ) {
			vdp_mode = 2;
//		} else
//		if ( ! M1 && ! M2 && M3 ) {
//			vdp_mode = 3;
		} else {
			logerror( "Unknown video mode detected (M1=%c, M2=%c, M3=%c, M4=%c)\n", M1 ? '1' : '0', M2 ? '1' : '0', M3 ? '1' : '0', M4 ? '1' : '0');
		}
	}
	switch( y_pixels ) {
	case 192:
		sms_frame_timing = ( Machine->screen[0].height == PAL_Y_PIXELS ) ? sms_pal_192 : sms_ntsc_192;
		break;
	case 224:
		sms_frame_timing = ( Machine->screen[0].height == PAL_Y_PIXELS ) ? sms_pal_224 : sms_ntsc_224;
		break;
	case 240:
		sms_frame_timing = ( Machine->screen[0].height == PAL_Y_PIXELS ) ? sms_pal_240 : sms_ntsc_240;
		break;
	}
	isCRAMDirty = 1;
}

 READ8_HANDLER(sms_vdp_vcount_r) {
	return ( sms_frame_timing[ INIT_VCOUNT ] + video_screen_get_vpos(0) ) & 0xFF;
}

READ8_HANDLER(sms_vdp_hcount_r) {
	return video_screen_get_hpos(0) >> 1;
}

void sms_set_ggsmsmode( int mode ) {
	ggSmsMode = mode;
}

int smsvdp_video_init( const smsvdp_configuration *config ) {

	features = config->model;
	int_callback = config->int_callback;

	/* Allocate video RAM
	   In theory the driver could have a REGION_GFX1 and/or REGION_GFX2 memory region
	   of it's own. So this code could potentially cause a clash.
	*/
	VRAM = new_memory_region( Machine, REGION_GFX1, VRAM_SIZE, ROM_REQUIRED );
	CRAM = new_memory_region( Machine, REGION_GFX2, MAX_CRAM_SIZE, ROM_REQUIRED );
	lineBuffer = auto_malloc( 256 * 5 * sizeof(int) );
	memset( lineBuffer, 0, 256 * 5 * sizeof(int) );

	/* Clear RAM */
	memset(reg, 0, NUM_OF_REGISTER);
	isCRAMDirty = 1;
	memset(VRAM, 0, VRAM_SIZE);
	memset(CRAM, 0, MAX_CRAM_SIZE);
	reg[0x01] |= 0x20;
	reg[0x02] = 0x0E;			/* power up default */
	reg[0x0a] = 0xff;

	CRAMMask = ( IS_GAMEGEAR_VDP && ! ggSmsMode ) ? ( GG_CRAM_SIZE - 1 ) : ( SMS_CRAM_SIZE - 1 );

	/* Initialize VDP state variables */
	addr = code = pending = latch = buffer = statusReg = \
	lineCountDownCounter = irqState = 0;

	lineCollisionBuffer = auto_malloc(SMS_X_PIXELS);

	/* Make temp bitmap for rendering */
	tmpbitmap = auto_bitmap_alloc(Machine->screen[0].width, Machine->screen[0].height, BITMAP_FORMAT_INDEXED32);

	prevBitMapSaved = 0;
	prevBitMap = auto_bitmap_alloc(Machine->screen[0].width, Machine->screen[0].height, BITMAP_FORMAT_INDEXED32);

	set_display_settings();

	smsvdp_display_timer = mame_timer_alloc( smsvdp_display_callback );
	mame_timer_adjust( smsvdp_display_timer, video_screen_get_time_until_pos( 0, 0, 0 ), 0, video_screen_get_scan_period( 0 ) );
	return (0);
}

static TIMER_CALLBACK(smsvdp_display_callback)
{
	rectangle rec;
	int vpos = video_screen_get_vpos(0);
	int vpos_limit = sms_frame_timing[VERTICAL_BLANKING] + sms_frame_timing[TOP_BLANKING]
	               + sms_frame_timing[TOP_BORDER] + sms_frame_timing[ACTIVE_DISPLAY_V]
	               + sms_frame_timing[BOTTOM_BORDER] + sms_frame_timing[BOTTOM_BLANKING];

	rec.min_y = rec.max_y = vpos;

	/* Check if we're on the last line of a frame */
	if ( vpos == vpos_limit - 1 ) {
		check_pause_button();
		return;
	}

	vpos_limit -= sms_frame_timing[BOTTOM_BLANKING];

	/* Check if we're below the bottom border */
	if ( vpos >= vpos_limit ) {
		return;
	}

	vpos_limit -= sms_frame_timing[BOTTOM_BORDER];

	/* Check if we're in the bottom border area */
	if ( vpos >= vpos_limit ) {
		if ( vpos == vpos_limit ) {
			if ( lineCountDownCounter == 0x00 ) {
				lineCountDownCounter = reg[0x0A];
				statusReg |= STATUS_HINT;
				irqState = 1;
				if ( reg[0x00] & 0x10 ) {
					if ( int_callback ) {
						int_callback( ASSERT_LINE );
					}
				}
			}

		}
		if ( vpos == vpos_limit + 1 ) {
			statusReg |= STATUS_VINT;
			irqState = 1;
			if ( reg[0x01] & 0x20 ) {
				if ( int_callback ) {
					int_callback( ASSERT_LINE );
				}
			}
		}
		if ( video_skip_this_frame() ) {
			return;
		}
		sms_update_palette();
		/* Draw left border */
		rec.min_x = LBORDER_START;
		rec.max_x = LBORDER_START + LBORDER_X_PIXELS - 1;
		fillbitmap( tmpbitmap, Machine->pens[currentPalette[BACKDROP_COLOR]], &rec );
		/* Draw right border */
		rec.min_x = LBORDER_START + LBORDER_X_PIXELS + 256;
		rec.max_x = rec.min_x + RBORDER_X_PIXELS - 1;
		fillbitmap( tmpbitmap, Machine->pens[currentPalette[BACKDROP_COLOR]], &rec );
		/* Draw middle of the border */
		/* We need to do this through the regular drawing function so it will */
		/* be included in the gamegear scaling functions */
		sms_refresh_line( tmpbitmap, LBORDER_START + LBORDER_X_PIXELS, vpos_limit - sms_frame_timing[ACTIVE_DISPLAY_V], vpos - ( vpos_limit - sms_frame_timing[ACTIVE_DISPLAY_V] ) );
		return;
	}

	vpos_limit -= sms_frame_timing[ACTIVE_DISPLAY_V];

	/* Check if we're in the active display area */
	if ( vpos >= vpos_limit ) {
		if ( vpos == vpos_limit ) {
			lineCountDownCounter = reg[0x0A];
			reg9copy = reg[0x09];
		}
		if ( lineCountDownCounter == 0x00 ) {
			lineCountDownCounter = reg[0x0A];
			statusReg |= STATUS_HINT;
			irqState = 1;
			if ( reg[0x00] & 0x10 ) {
				if ( int_callback ) {
					int_callback( ASSERT_LINE );
				}
			}
		} else {
			lineCountDownCounter -= 1;
		}
		if ( video_skip_this_frame() ) {
			return;
		}
		sms_update_palette();

		/* Check if display is disabled */
		if ( ! ( reg[0x01] & 0x40 ) ) {
			/* set whole line to backdrop color */
			rec.min_x = LBORDER_START;
			rec.max_x = LBORDER_START + LBORDER_X_PIXELS + 255 + RBORDER_X_PIXELS;
			fillbitmap( tmpbitmap, Machine->pens[currentPalette[BACKDROP_COLOR]], &rec );
		} else {
			/* Draw left border */
			rec.min_x = LBORDER_START;
			rec.max_x = LBORDER_START + LBORDER_X_PIXELS - 1;
			fillbitmap( tmpbitmap, Machine->pens[currentPalette[BACKDROP_COLOR]], &rec );
			/* Draw right border */
			rec.min_x = LBORDER_START + LBORDER_X_PIXELS + 256;
			rec.max_x = rec.min_x + RBORDER_X_PIXELS - 1;
			fillbitmap( tmpbitmap, Machine->pens[currentPalette[BACKDROP_COLOR]], &rec );
			sms_refresh_line( tmpbitmap, LBORDER_START + LBORDER_X_PIXELS, vpos_limit, vpos - vpos_limit );
		}
		return;
	}

	vpos_limit -= sms_frame_timing[TOP_BORDER];

	/* Check if we're in the top border area */
	if ( vpos >= vpos_limit ) {
		if ( video_skip_this_frame() ) {
			return;
		}
		sms_update_palette();
		/* Draw left border */
		rec.min_x = LBORDER_START;
		rec.max_x = LBORDER_START + LBORDER_X_PIXELS - 1;
		fillbitmap( tmpbitmap, Machine->pens[currentPalette[BACKDROP_COLOR]], &rec );
		/* Draw right border */
		rec.min_x = LBORDER_START + LBORDER_X_PIXELS + 256;
		rec.max_x = rec.min_x + RBORDER_X_PIXELS - 1;
		fillbitmap( tmpbitmap, Machine->pens[currentPalette[BACKDROP_COLOR]], &rec );
		/* Draw middle of the border */
		/* We need to do this through the regular drawing function so it will */
		/* be included in the gamegear scaling functions */
		sms_refresh_line( tmpbitmap, LBORDER_START + LBORDER_X_PIXELS, vpos_limit + sms_frame_timing[TOP_BORDER], vpos - ( vpos_limit + sms_frame_timing[TOP_BORDER] ) );
		return;
	}
}

 READ8_HANDLER(sms_vdp_data_r) {
	int temp;

	/* SMS 2 & GG behaviour. Seems like the latched data is passed straight through */
	/* to the address register when in the middle of doing a command.               */
	/* Cosmic Spacehead needs this, among others                                    */
	if ( pending ) {
		addr = ( addr & 0xff00 ) | latch;
		/* Clear pending write flag */
		pending = 0;
	}

	/* Return read buffer contents */
	temp = buffer;

	/* Load read buffer */
	buffer = VRAM[(addr & 0x3FFF)];

	/* Bump internal address register */
	addr += 1;
	return (temp);
}

 READ8_HANDLER(sms_vdp_ctrl_r) {
	int temp = statusReg;

	/* Clear pending write flag */
	pending = 0;

	statusReg &= ~( STATUS_VINT | STATUS_SPROVR | STATUS_SPRCOL | STATUS_HINT );

	if (irqState == 1) {
		irqState = 0;
		if ( int_callback ) {
			int_callback( CLEAR_LINE );
		}
	}

	return (temp);
}

WRITE8_HANDLER(sms_vdp_data_w) {
	/* SMS 2 & GG behaviour. Seems like the latched data is passed straight through */
	/* to the address register when in the middle of doing a command.               */
        /* Cosmic Spacehead needs this, among others                                    */
	if ( pending ) {
		addr = ( addr & 0xff00 ) | latch;
		/* Clear pending write flag */
		pending = 0;
	}

	switch(code) {
		case 0x00:
		case 0x01:
		case 0x02: {
			int address = (addr & 0x3FFF);

			VRAM[address] = data;
		}
		break;
		case 0x03: {
			int address = addr & CRAMMask;

			if (data != CRAM[address]) {
				CRAM[address] = data;
				isCRAMDirty = 1;
			}
		}
		break;
	}

	//buffer = data;
	addr += 1;
}

WRITE8_HANDLER(sms_vdp_ctrl_w) {
	int regNum;

	if (pending == 0) {
		latch = data;
		pending = 1;
	} else {
		/* Clear pending write flag */
		pending = 0;

		code = (data >> 6) & 0x03;
		switch( code ) {
		case 0:		/* VRAM reading mode */
			addr = ( data << 8 ) | latch;
			buffer = VRAM[ addr & 0x3FFF ];
			addr += 1;
			break;
		case 1:		/* VRAM writing mode */
			addr = ( data << 8 ) | latch;
			break;
		case 2:		/* VDP register write */
			regNum = data & 0x0F;
			reg[regNum] = latch;
			if (regNum == 0 && latch & 0x02) {
				logerror("overscan enabled.\n");
			}
			if ( regNum == 0 || regNum == 1 ) {
				set_display_settings();
			}
			if ( ( regNum == 1 ) && ( reg[0x01] & 0x20 ) && ( statusReg & STATUS_VINT ) ) {
				int_callback( ASSERT_LINE );
			}
			code = 0;
			break;
		case 3:		/* CRAM writing mode */
			addr = ( data << 8 ) | latch;
			break;
		}
	}
}

void sms_refresh_line_mode4(int *lineBuffer, int line) {
	int tileColumn;
	int xScroll, yScroll, xScrollStartColumn;
	int spriteIndex;
	int pixelX, pixelPlotX, prioritySelected[256];
	int spriteX, spriteY, spriteLine, spriteTileSelected, spriteHeight, spriteZoom;
	int spriteBuffer[8], spriteBufferCount, spriteBufferIndex;
	int bitPlane0, bitPlane1, bitPlane2, bitPlane3;
	UINT16 nameTableAddress;
	UINT8 *nameTable;
	UINT8 *spriteTable = &VRAM[(reg[0x05] << 7) & 0x3F00];

	if ( y_pixels != 192 ) {
		nameTableAddress = (((reg[0x02] & 0x0C) << 10) | 0x0700) + ((((line + reg9copy) % 256) >> 3) << 6);
	} else {
		nameTableAddress = ((reg[0x02] << 10) & 0x3800) + ((((line + reg9copy) % 224) >> 3) << 6);
	}
	if ( IS_SMS1_VDP ) {
		nameTableAddress = nameTableAddress & (((reg[0x02] & 0x01) << 10) | 0x3BFF);
	}
	nameTable = VRAM + nameTableAddress;

	/* if top 2 rows of screen not affected by horizontal scrolling, then xScroll = 0 */
	/* else xScroll = reg[0x08] (SMS Only)                                            */
	if ( IS_GAMEGEAR_VDP ) {
		xScroll = 0x0100 - reg[0x08];
	} else {
		xScroll = (((reg[0x00] & 0x40) && (line < 16)) ? 0 : 0x0100 - reg[0x08]);
	}

	xScrollStartColumn = (xScroll >> 3);			 /* x starting column tile */

	/* Draw background layer */
	for (tileColumn = 0; tileColumn < 33; tileColumn++) {
		UINT16 tileData;
		int tileSelected, palletteSelected, horizSelected, vertSelected, prioritySelect;
		int tileLine;

		/* Rightmost 8 columns for SMS (or 2 columns for GG) not affected by */
		/* vertical scrolling when bit 7 of reg[0x00] is set */
		if ( IS_GAMEGEAR_VDP ) {
			yScroll = (((reg[0x00] & 0x80) && (tileColumn > 29)) ? 0 : (reg9copy) % 224);
		} else {
			yScroll = (((reg[0x00] & 0x80) && (tileColumn > 23)) ? 0 : (reg9copy) % 224);
		}

		tileLine = ( ( tileColumn + xScrollStartColumn ) & 0x1F ) * 2;
		tileData = nameTable[ tileLine ] | ( nameTable[ tileLine + 1 ] << 8 );

		tileSelected = (tileData & 0x01FF);
		prioritySelect = tileData & PRIORITY_BIT;
		palletteSelected = (tileData >> 11) & 0x01;
		vertSelected = (tileData >> 10) & 0x01;
		horizSelected = (tileData >> 9) & 0x01;

		tileLine = line - ((0x07 - (yScroll & 0x07)) + 1);
		if (vertSelected) {
			tileLine = 0x07 - tileLine;
		}
		bitPlane0 = VRAM[((tileSelected << 5) + ((tileLine & 0x07) << 2)) + 0x00];
		bitPlane1 = VRAM[((tileSelected << 5) + ((tileLine & 0x07) << 2)) + 0x01];
		bitPlane2 = VRAM[((tileSelected << 5) + ((tileLine & 0x07) << 2)) + 0x02];
		bitPlane3 = VRAM[((tileSelected << 5) + ((tileLine & 0x07) << 2)) + 0x03];

		for (pixelX = 0; pixelX < 8 ; pixelX++) {
			UINT8 penBit0, penBit1, penBit2, penBit3;
			UINT8 penSelected;

			penBit0 = (bitPlane0 >> (7 - pixelX)) & 0x01;
			penBit1 = (bitPlane1 >> (7 - pixelX)) & 0x01;
			penBit2 = (bitPlane2 >> (7 - pixelX)) & 0x01;
			penBit3 = (bitPlane3 >> (7 - pixelX)) & 0x01;

			penSelected = (penBit3 << 3 | penBit2 << 2 | penBit1 << 1 | penBit0);
			if (palletteSelected) {
				penSelected |= 0x10;
			}

			if (!horizSelected) {
				pixelPlotX = pixelX;
			} else {
				pixelPlotX = 7 - pixelX;
			}
			pixelPlotX = (0 - (xScroll & 0x07) + (tileColumn << 3) + pixelPlotX);
			if (pixelPlotX >= 0 && pixelPlotX < 256) {
//				logerror("%x %x\n", pixelPlotX + pixelOffsetX, pixelPlotY);
				lineBuffer[pixelPlotX] = currentPalette[penSelected];
				prioritySelected[pixelPlotX] = prioritySelect | ( penSelected & 0x0F );
			}
		}
	}

	/* Draw sprite layer */
	spriteHeight = (reg[0x01] & 0x02 ? 16 : 8);
	spriteZoom = 1;
	if (reg[0x01] & 0x01) {
		/* sprite doubling */
		spriteZoom = 2;
	}
	spriteBufferCount = 0;
	for (spriteIndex = 0; (spriteIndex < 64) && (spriteTable[spriteIndex] != 0xD0 || y_pixels != 192) && (spriteBufferCount < 9); spriteIndex++) {
		spriteY = spriteTable[spriteIndex] + 1; /* sprite y position starts at line 1 */
		if (spriteY > 240) {
			spriteY -= 256; /* wrap from top if y position is > 240 */
		}
		if ((line >= spriteY) && (line < (spriteY + spriteHeight * spriteZoom))) {
			if (spriteBufferCount < 8) {
				spriteBuffer[spriteBufferCount] = spriteIndex;
			} else {
				/* Too many sprites per line */
				statusReg |= STATUS_SPROVR;
			}
			spriteBufferCount++;
		}
	}
	if ( spriteBufferCount > 8 ) {
		spriteBufferCount = 8;
	}
	memset(lineCollisionBuffer, 0, SMS_X_PIXELS);
	spriteBufferCount--;
	for (spriteBufferIndex = spriteBufferCount; spriteBufferIndex >= 0; spriteBufferIndex--) {
		spriteIndex = spriteBuffer[spriteBufferIndex];
		spriteY = spriteTable[spriteIndex] + 1; /* sprite y position starts at line 1 */
		if (spriteY > 240) {
			spriteY -= 256; /* wrap from top if y position is > 240 */
		}

		spriteX = spriteTable[0x80 + (spriteIndex << 1)];
		if (reg[0x00] & 0x08) {
			spriteX -= 0x08;	 /* sprite shift */
		}
		spriteTileSelected = spriteTable[0x81 + (spriteIndex << 1)];
		if (reg[0x06] & 0x04) {
			spriteTileSelected += 256; /* pattern table select */
		}
		if (reg[0x01] & 0x02) {
			spriteTileSelected &= 0x01FE; /* force even index */
		}
		spriteLine = ( line - spriteY ) / spriteZoom;

		if (spriteLine > 0x07) {
			spriteTileSelected += 1;
		}

		bitPlane0 = VRAM[((spriteTileSelected << 5) + ((spriteLine & 0x07) << 2)) + 0x00];
		bitPlane1 = VRAM[((spriteTileSelected << 5) + ((spriteLine & 0x07) << 2)) + 0x01];
		bitPlane2 = VRAM[((spriteTileSelected << 5) + ((spriteLine & 0x07) << 2)) + 0x02];
		bitPlane3 = VRAM[((spriteTileSelected << 5) + ((spriteLine & 0x07) << 2)) + 0x03];

		for (pixelX = 0; pixelX < 8 ; pixelX++) {
			UINT8 penBit0, penBit1, penBit2, penBit3;
			int penSelected;

			penBit0 = (bitPlane0 >> (7 - pixelX)) & 0x01;
			penBit1 = (bitPlane1 >> (7 - pixelX)) & 0x01;
			penBit2 = (bitPlane2 >> (7 - pixelX)) & 0x01;
			penBit3 = (bitPlane3 >> (7 - pixelX)) & 0x01;

			penSelected = (penBit3 << 3 | penBit2 << 2 | penBit1 << 1 | penBit0) | 0x10;

			if ( penSelected == 0x10 ) {	/* Transparent palette so skip draw */
				continue;
			}

			if (reg[0x01] & 0x01) {
				/* sprite doubling is enabled */
				pixelPlotX = spriteX + (pixelX << 1);

				/* check to prevent going outside of active display area */
				if ( pixelPlotX > 256 ) {
					continue;
				}

				if ( ! ( prioritySelected[pixelPlotX] & PRIORITY_BIT ) ) {
					lineBuffer[pixelPlotX] = currentPalette[penSelected];
					lineBuffer[pixelPlotX+1] = currentPalette[penSelected];
				} else {
					if ( prioritySelected[pixelPlotX] == PRIORITY_BIT ) {
						lineBuffer[pixelPlotX] = currentPalette[penSelected];
					}
					if ( prioritySelected[pixelPlotX + 1] == PRIORITY_BIT ) {
						lineBuffer[pixelPlotX+1] = currentPalette[penSelected];
					}
				}
				if (lineCollisionBuffer[pixelPlotX] != 1) {
					lineCollisionBuffer[pixelPlotX] = 1;
				} else {
					/* sprite collision occurred */
					statusReg |= STATUS_SPRCOL;
				}
				if (lineCollisionBuffer[pixelPlotX + 1] != 1) {
					lineCollisionBuffer[pixelPlotX + 1] = 1;
				} else {
					/* sprite collision occurred */
					statusReg |= STATUS_SPRCOL;
				}
			} else {
				pixelPlotX = spriteX + pixelX;

				/* check to prevent going outside of active display area */
				if ( pixelPlotX > 256 ) {
					continue;
				}

				if ( ! ( prioritySelected[pixelPlotX] & PRIORITY_BIT ) ) {
					lineBuffer[pixelPlotX] = currentPalette[penSelected];
				} else {
					if ( prioritySelected[pixelPlotX] == PRIORITY_BIT ) {
						lineBuffer[pixelPlotX] = currentPalette[penSelected];
					}
				}
				if (lineCollisionBuffer[pixelPlotX] != 1) {
					lineCollisionBuffer[pixelPlotX] = 1;
				} else {
					/* sprite collision occurred */
					statusReg |= STATUS_SPRCOL;
				}
			}
		}
	}

	/* Fill column 0 with overscan color from reg[0x07] */
	if (reg[0x00] & 0x20) {
		lineBuffer[0] = currentPalette[BACKDROP_COLOR];
		lineBuffer[1] = currentPalette[BACKDROP_COLOR];
		lineBuffer[2] = currentPalette[BACKDROP_COLOR];
		lineBuffer[3] = currentPalette[BACKDROP_COLOR];
		lineBuffer[4] = currentPalette[BACKDROP_COLOR];
		lineBuffer[5] = currentPalette[BACKDROP_COLOR];
		lineBuffer[6] = currentPalette[BACKDROP_COLOR];
		lineBuffer[7] = currentPalette[BACKDROP_COLOR];
	}
}

void sms_refresh_tms9918_sprites(int *lineBuffer, int line) {
	int pixelPlotX;
	int spriteHeight, spriteBufferCount, spriteIndex, spriteBuffer[4], spriteBufferIndex;
	UINT8 *spriteTable, *spritePatternTable;

	/* Draw sprite layer */
	spriteTable = VRAM + ( ( reg[0x05] & 0x7F ) << 7 );
	spritePatternTable = VRAM + ( ( reg[0x06] & 0x07 ) << 11 );
	spriteHeight = 8;
	if ( reg[0x01] & 0x02 )                         /* Check if SI is set */
		spriteHeight = spriteHeight * 2;
	if ( reg[0x01] & 0x01 )                         /* Check if MAG is set */
		spriteHeight = spriteHeight * 2;
	spriteBufferCount = 0;
	for ( spriteIndex = 0; (spriteIndex < 32*4 ) && ( spriteTable[spriteIndex] != 0xD0 ) && ( spriteBufferCount < 5); spriteIndex+= 4 ) {
		int spriteY = spriteTable[spriteIndex] + 1;
		if ( spriteY > 240 ) {
			spriteY -= 256;
		}
		if ( ( line >= spriteY ) && ( line < ( spriteY + spriteHeight ) ) ) {
			if ( spriteBufferCount < 5 ) {
				spriteBuffer[spriteBufferCount] = spriteIndex;
			} else {
				/* Too many sprites per line */
				statusReg |= STATUS_SPROVR;
			}
			spriteBufferCount++;
		}
	}
	if ( spriteBufferCount > 4 ) {
		spriteBufferCount = 4;
	}
	memset( lineCollisionBuffer, 0, SMS_X_PIXELS );
	spriteBufferCount--;
	for ( spriteBufferIndex = spriteBufferCount; spriteBufferIndex >= 0; spriteBufferIndex-- ) {
		int penSelected;
		int spriteLine, pixelX, spriteX, spriteTileSelected;
		int spriteY;
		UINT8 pattern;
		spriteIndex = spriteBuffer[ spriteBufferIndex ];
		spriteY = spriteTable[ spriteIndex ] + 1;
		if ( spriteY > 240 ) {
			spriteY -= 256;
		}
		spriteX = spriteTable[ spriteIndex + 1 ];
		penSelected = spriteTable[ spriteIndex + 3 ] & 0x0F;
		if ( IS_GAMEGEAR_VDP ) {
			penSelected |= 0x10;
		}
		if ( spriteTable[ spriteIndex + 3 ] & 0x80 ) {
			spriteX -= 32;
		}
		spriteTileSelected = spriteTable[ spriteIndex + 2 ];
		spriteLine = line - spriteY;
		if ( reg[0x01] & 0x01 ) {
			spriteLine >>= 1;
		}
		if ( reg[0x01] & 0x02 ) {
			spriteTileSelected &= 0xFC;
			if ( spriteLine > 0x07 ) {
				spriteTileSelected += 1;
				spriteLine -= 8;
			}
		}
		pattern = spritePatternTable[ spriteTileSelected * 8 + spriteLine ];

		for ( pixelX = 0; pixelX < 8; pixelX++ ) {
			if ( reg[0x01] & 0x01 ) {
				pixelPlotX = spriteX + pixelX * 2;
				if ( pixelPlotX < 0 || pixelPlotX > 255 ) {
					continue;
				}
				if ( penSelected && ( pattern & ( 1 << ( 7 - pixelX ) ) ) ) {
					lineBuffer[pixelPlotX] = currentPalette[penSelected];
					if ( lineCollisionBuffer[pixelPlotX] != 1 ) {
						lineCollisionBuffer[pixelPlotX] = 1;
					} else {
						statusReg |= STATUS_SPRCOL;
					}
					lineBuffer[pixelPlotX+1] = currentPalette[penSelected];
					if ( lineCollisionBuffer[pixelPlotX + 1] != 1 ) {
						lineCollisionBuffer[pixelPlotX + 1] = 1;
					} else {
						statusReg |= STATUS_SPRCOL;
					}
				}
			} else {
				pixelPlotX = spriteX + pixelX;
				if ( pixelPlotX < 0 || pixelPlotX > 255 ) {
					continue;
				}
				if ( penSelected && ( pattern & ( 1 << ( 7 - pixelX ) ) ) ) {
					lineBuffer[pixelPlotX] = currentPalette[penSelected];
					if ( lineCollisionBuffer[pixelPlotX] != 1 ) {
						lineCollisionBuffer[pixelPlotX] = 1;
					} else {
						statusReg |= STATUS_SPRCOL;
					}
				}
			}
		}
	
		if ( reg[0x01] & 0x02 ) {
			spriteTileSelected += 2;
			pattern = spritePatternTable[ spriteTileSelected * 8 + spriteLine ];
			spriteX += ( reg[0x01] & 0x01 ? 16 : 8 );
			for ( pixelX = 0; pixelX < 8; pixelX++ ) {
				if ( reg[0x01] & 0x01 ) {
					pixelPlotX = spriteX + pixelX * 2;
					if ( pixelPlotX < 0 || pixelPlotX > 255 ) {
						continue;
					}
					if ( penSelected && ( pattern & ( 1 << ( 7 - pixelX ) ) ) ) {
						lineBuffer[pixelPlotX] = currentPalette[penSelected];
						if ( lineCollisionBuffer[pixelPlotX] != 1 ) {
							lineCollisionBuffer[pixelPlotX] = 1;
						} else {
							statusReg |= STATUS_SPRCOL;
						}
						lineBuffer[pixelPlotX+1] = currentPalette[penSelected];
						if ( lineCollisionBuffer[pixelPlotX + 1] != 1 ) {
							lineCollisionBuffer[pixelPlotX + 1] = 1;
						} else {
							statusReg |= STATUS_SPRCOL;
						}
					}
				} else {
					pixelPlotX = spriteX + pixelX;
					if ( pixelPlotX < 0 || pixelPlotX > 255 ) {
						continue;
					}
					if ( penSelected && ( pattern & ( 1 << ( 7 - pixelX ) ) ) ) {
						lineBuffer[pixelPlotX] = currentPalette[penSelected];
						if ( lineCollisionBuffer[pixelPlotX] != 1 ) {
							lineCollisionBuffer[pixelPlotX] = 1;
						} else {
							statusReg |= STATUS_SPRCOL;
						}
					}
				}
			}
		}
	}
}

void sms_refresh_line_mode2(int *lineBuffer, int line) {
	int tileColumn;
	int pixelX, pixelPlotX;
	UINT8 *nameTable, *colorTable, *patternTable;
	int patternMask, colorMask, patternOffset;

	/* Draw background layer */
	nameTable = VRAM + ( ( reg[0x02] & 0x0F ) << 10 ) + ( ( line >> 3 ) * 32 );
	colorTable = VRAM + ( ( reg[0x03] & 0x80 ) << 6 );
	colorMask = ( ( reg[0x03] & 0x7F ) << 3 ) | 0x07;
	patternTable = VRAM + ( ( reg[0x04] & 0x04 ) << 11 );
	patternMask = ( ( reg[0x04] & 0x03 ) << 8 ) | 0xFF;
	patternOffset = ( line & 0xC0 ) << 2;
	for ( tileColumn = 0; tileColumn < 32; tileColumn++ ) {
		UINT8 pattern;
		UINT8 colors;
		pattern = patternTable[ ( ( ( patternOffset + nameTable[tileColumn] ) & patternMask ) * 8 ) + ( line & 0x07 ) ];
		colors = colorTable[ ( ( ( patternOffset + nameTable[tileColumn] ) & colorMask ) * 8 ) + ( line & 0x07 ) ];
		for ( pixelX = 0; pixelX < 8; pixelX++ ) {
			UINT8 penSelected;
			if ( pattern & ( 1 << ( 7 - pixelX ) ) ) {
				penSelected = colors >> 4;
			} else {
				penSelected = colors & 0x0F;
			} 
			if ( ! penSelected ) {
				penSelected = BACKDROP_COLOR;
			}
			pixelPlotX = ( tileColumn << 3 ) + pixelX;
			if ( IS_GAMEGEAR_VDP ) {
				penSelected |= 0x10;
			}
			lineBuffer[pixelPlotX] = currentPalette[penSelected];
		}
	}

	/* Draw sprite layer */
	sms_refresh_tms9918_sprites( lineBuffer, line );
}

void sms_refresh_line_mode0(int *lineBuffer, int line) {
	int tileColumn;
	int pixelX, pixelPlotX; 
	UINT8 *nameTable, *colorTable, *patternTable;

	/* Draw background layer */
	nameTable = VRAM + ( ( reg[0x02] & 0x0F ) << 10 ) + ( ( line >> 3 ) * 32 );
	colorTable = VRAM + ( ( reg[0x03] << 6 ) & ( VRAM_SIZE - 1 ) );
	patternTable = VRAM + ( ( reg[0x04] << 11 ) & ( VRAM_SIZE - 1 ) ); 
	for ( tileColumn = 0; tileColumn < 32; tileColumn++ ) {
		UINT8 pattern;
		UINT8 colors;
		pattern = patternTable[ ( nameTable[tileColumn] * 8 ) + ( line & 0x07 ) ];
		colors = colorTable[ nameTable[tileColumn] >> 3 ];
		for ( pixelX = 0; pixelX < 8; pixelX++ ) {
			int penSelected;
			if ( pattern & ( 1 << ( 7 - pixelX ) ) ) {
				penSelected = colors >> 4;
			} else {
				penSelected = colors & 0x0F;
			}
			if ( IS_GAMEGEAR_VDP ) {
				penSelected |= 0x10;
			}
			pixelPlotX = ( tileColumn << 3 ) + pixelX;
			lineBuffer[pixelPlotX] = currentPalette[penSelected];
		}
	}

	/* Draw sprite layer */
	sms_refresh_tms9918_sprites( lineBuffer, line );
}

void sms_refresh_line( mame_bitmap *bitmap, int pixelOffsetX, int pixelPlotY, int line ) {
	int x;
	int *blitLineBuffer = lineBuffer;

	if ( line >= 0 && line < sms_frame_timing[ACTIVE_DISPLAY_V] ) {
		switch( vdp_mode ) {
		case 0:
			sms_refresh_line_mode0( blitLineBuffer, line );
			break;
		case 2:
			sms_refresh_line_mode2( blitLineBuffer, line );
			break;
		case 4:
		default:
			sms_refresh_line_mode4( blitLineBuffer, line );
			break;
		}
	} else {
		for ( x = 0; x < 256; x++ ) {
			blitLineBuffer[x] = currentPalette[BACKDROP_COLOR];
		}
	}

	if ( IS_GAMEGEAR_VDP && ggSmsMode ) {
		int *combineLineBuffer = lineBuffer + ( ( line & 0x03 ) + 1 ) * 256;
		int plotX = 48;

		/* Do horizontal scaling */
		for( x = 8; x < 248; ) {
			int	combined;

			/* Take red and green from first pixel, and blue from second pixel */
			combined = ( blitLineBuffer[x] & 0x00FF ) | ( blitLineBuffer[x+1] & 0x0F00 );
			combineLineBuffer[plotX] = combined;

			/* Take red from second pixel, and green and blue from third pixel */
			combined = ( blitLineBuffer[x+1] & 0x000F ) | ( blitLineBuffer[x+2] & 0x0FF0 );
			combineLineBuffer[plotX+1] = combined;
			x += 3;
			plotX += 2;
		}

		/* Do vertical scaling for a screen with 192 or 224 lines
		   Lines 0-2 and 221-223 have no effect on the output on the GG screen.
		   We will calculate the gamegear lines as follows:
		   GG_0 = 1/6 * SMS_3 + 1/3 * SMS_4 + 1/3 * SMS_5 + 1/6 * SMS_6
		   GG_1 = 1/6 * SMS_4 + 1/3 * SMS_5 + 1/3 * SMS_6 + 1/6 * SMS_7
		   GG_2 = 1/6 * SMS_6 + 1/3 * SMS_7 + 1/3 * SMS_8 + 1/6 * SMS_9
		   GG_3 = 1/6 * SMS_7 + 1/3 * SMS_8 + 1/3 * SMS_9 + 1/6 * SMS_10
		   GG_4 = 1/6 * SMS_9 + 1/3 * SMS_10 + 1/3 * SMS_11 + 1/6 * SMS_12
		   .....
		   GG_142 = 1/6 * SMS_216 + 1/3 * SMS_217 + 1/3 * SMS_218 + 1/6 * SMS_219
		   GG_143 = 1/6 * SMS_217 + 1/3 * SMS_218 + 1/3 * SMS_219 + 1/6 * SMS_220
		*/
		{
			int	ggLine;
			int	myLine = pixelPlotY + line - ( TBORDER_START + NTSC_224_TBORDER_Y_PIXELS );
			int	*line1, *line2, *line3, *line4;

			/* First make sure there's enough data to draw anything */
			/* We need one more line of data if we're on line 8, 11, 14, 17, etc */
			if ( myLine < 6 || myLine > 220 || ( ( myLine - 8 ) % 3 == 0 ) ) {
				return;
			}
			ggLine = ( ( myLine - 6 ) / 3 ) * 2;
			/* If we're on SMS line 7, 10, 13, etc we're on an odd GG line */
			if ( myLine % 3 ) {
				ggLine++;
			}
			/* Calculate the line we will be drawing on */
			pixelPlotY = TBORDER_START + NTSC_192_TBORDER_Y_PIXELS + 24 + ggLine;

			/* Setup our source lines */
			line1 = lineBuffer + ( ( ( myLine - 3 ) & 0x03 ) + 1 ) * 256;
			line2 = lineBuffer + ( ( ( myLine - 2 ) & 0x03 ) + 1 ) * 256;
			line3 = lineBuffer + ( ( ( myLine - 1 ) & 0x03 ) + 1 ) * 256;
			line4 = lineBuffer + ( ( ( myLine - 0 ) & 0x03 ) + 1 ) * 256;

			for( x = 0+48; x < 160+48; x++ ) {
				rgb_t	c1 = Machine->pens[line1[x]];
				rgb_t	c2 = Machine->pens[line2[x]];
				rgb_t	c3 = Machine->pens[line3[x]];
				rgb_t	c4 = Machine->pens[line4[x]];
				*BITMAP_ADDR32( bitmap, pixelPlotY, pixelOffsetX + x) =
					MAKE_RGB( ( RGB_RED(c1)/6 + RGB_RED(c2)/3 + RGB_RED(c3)/3 + RGB_RED(c4)/6 ),
						( RGB_GREEN(c1)/6 + RGB_GREEN(c2)/3 + RGB_GREEN(c3)/3 + RGB_GREEN(c4)/6 ),
						( RGB_BLUE(c1)/6 + RGB_BLUE(c2)/3 + RGB_BLUE(c3)/3 + RGB_BLUE(c4)/6 ) );
			}
			return;
		}
		blitLineBuffer = combineLineBuffer;
	}

	for( x = 0; x < 256; x++ ) {
		*BITMAP_ADDR32( bitmap, pixelPlotY + line, pixelOffsetX + x) = Machine->pens[blitLineBuffer[x]];
	}
}

void sms_update_palette(void) {
	int i;

	/* Exit if palette is has no changes */
	if (isCRAMDirty == 0) {
		return;
	}
	isCRAMDirty = 0;

	if ( vdp_mode != 4 && ! IS_GAMEGEAR_VDP ) {
		for( i = 0; i < 16; i++ ) {
			currentPalette[i] = 64+i;
		}
		return;
	}

	if ( IS_GAMEGEAR_VDP ) {
		if ( ggSmsMode ) {
			for ( i = 0; i < 32; i++ ) {
				currentPalette[i] = ( ( CRAM[i] & 0x30 ) << 6 ) | ( ( CRAM[i] & 0x0C ) << 4 ) | ( ( CRAM[i] & 0x03 ) << 2 );
			}
		} else {
			for ( i = 0; i < 32; i++ ) {
				currentPalette[i] = ( ( CRAM[i*2+1] << 8 ) | CRAM[i*2] ) & 0x0FFF;
			}
		}
	} else {
		for ( i = 0; i < 32; i++ ) {
			currentPalette[i] = CRAM[i] & 0x3F;
		}
	}
}

VIDEO_UPDATE(sms) {
	int x, y;

	if (prevBitMapSaved) {
	for (y = 0; y < Machine->screen[0].height; y++) {
		for (x = 0; x < Machine->screen[0].width; x++) {
			*BITMAP_ADDR32(bitmap, y, x) = (*BITMAP_ADDR32(tmpbitmap, y, x) + *BITMAP_ADDR32(prevBitMap, y, x)) >> 2;
			logerror("%x %x %x\n", *BITMAP_ADDR32(tmpbitmap, y, x), *BITMAP_ADDR32(prevBitMap, y, x), (*BITMAP_ADDR32(tmpbitmap, y, x) + *BITMAP_ADDR32(prevBitMap, y, x)) >> 2);
		}
	}
	} else {
		copybitmap(bitmap, tmpbitmap, 0, 0, 0, 0, &Machine->screen[0].visarea, TRANSPARENCY_NONE, 0);
	}
	if (!prevBitMapSaved) {
		copybitmap(prevBitMap, tmpbitmap, 0, 0, 0, 0, &Machine->screen[0].visarea, TRANSPARENCY_NONE, 0);
	//prevBitMapSaved = 1;
	}
	return 0;
}