{$ifdef NDS_INTERFACE}
type
  bg_scroll = record
    x: cuint16;
    y: cuint16;
  end;
  Tbg_scroll = bg_scroll;
  Pbg_scroll = ^bg_scroll;

  bg_transform = record
    hdx: cint16;
    vdx: cint16;
    hdy: cint16;
    vdy: cint16;
    dx: cint32;
    dy: cint32;
  end;
  Tbg_transform = bg_transform;
  Pbg_transform = ^bg_transform;

  bg_attribute = record
    control: array [0..3] of cuint16;
    scroll: array [0..3] of bg_scroll;
    bg2_rotation: bg_transform;
    bg3_rotation: bg_transform;
  end;
  Tbg_attribute = bg_attribute;
  Pbg_attribute = ^bg_attribute;


const
  MAP_BASE_SHIFT = 8;
  TILE_BASE_SHIFT = 2;

function BG_TILE_BASE(base: cint): cint; inline; 
function BG_MAP_BASE(base: cint): cint; inline;  
function BG_BMP_BASE(base: cint): cint; inline;  
function BG_PRIORITY(n: cint): cint; inline;
function TILE_PALETTE(n: cint): cint; inline;

const
  TILE_FLIP_H = (1 shl 10);
  TILE_FLIP_V = (1 shl 11);

type
  BackgroundControl = cint;
const
  BG_32x32: BackgroundControl = (0 shl 14);
  BG_64x32: BackgroundControl = (1 shl 14);
  BG_32x64: BackgroundControl = (2 shl 14);
  BG_64x64: BackgroundControl = (3 shl 14);
  
  BG_RS_16x16: BackgroundControl =  (0 shl 14);
  BG_RS_32x32: BackgroundControl =  (1 shl 14);
  BG_RS_64x64: BackgroundControl =  (2 shl 14);
  BG_RS_128x128: BackgroundControl =  (3 shl 14);
  
  BG_BMP8_128x128: BackgroundControl = ((0 shl 14) or (1 shl 7));
  BG_BMP8_256x256: BackgroundControl = ((1 shl 14) or (1 shl 7));
  BG_BMP8_512x256: BackgroundControl = ((2 shl 14) or (1 shl 7));
  BG_BMP8_512x512: BackgroundControl = ((3 shl 14) or (1 shl 7));
  BG_BMP8_1024x512: BackgroundControl = (1 shl 14);
  BG_BMP8_512x1024: BackgroundControl = 0;
  
  BG_BMP16_128x128: BackgroundControl = ((0 shl 14) or (1 shl 7) or (1 shl 2));
  BG_BMP16_256x256: BackgroundControl = ((1 shl 14) or (1 shl 7) or (1 shl 2));
  BG_BMP16_512x256: BackgroundControl = ((2 shl 14) or (1 shl 7) or (1 shl 2));
  BG_BMP16_512x512: BackgroundControl = ((3 shl 14) or (1 shl 7) or (1 shl 2));
  
  BG_MOSAIC_ON: BackgroundControl = ((1 shl 6));
  BG_MOSAIC_OFF: BackgroundControl = (0);
  
  BG_PRIORITY_0: BackgroundControl = (0);
  BG_PRIORITY_1: BackgroundControl = (1);
  BG_PRIORITY_2: BackgroundControl = (2);
  BG_PRIORITY_3: BackgroundControl = (3);
  
  BG_WRAP_OFF: BackgroundControl = (0);
  BG_WRAP_ON: BackgroundControl = (1 shl 13);
  
  BG_PALETTE_SLOT0: BackgroundControl = 0;
  BG_PALETTE_SLOT1: BackgroundControl = 0;
  BG_PALETTE_SLOT2: BackgroundControl = (1 shl 13);
  BG_PALETTE_SLOT3: BackgroundControl = (1 shl 13);
  
  BG_COLOR_256: BackgroundControl = $80;
  BG_COLOR_16: BackgroundControl = $00;

	BACKGROUND: Pbg_attribute = pointer($04000008);
  BG_OFFSET: Pbg_scroll = pointer($04000010);

function BG_MAP_RAM(base: cint): pcuint16; inline;  
function BG_TILE_RAM(base: cint): pcuint16; inline; 
function BG_BMP_RAM(base: cint): pcuint16; inline;  
function CHAR_BASE_BLOCK(n: cint): pcuint16; inline;
function SCREEN_BASE_BLOCK(n: cint): pcuint16; inline;

const
  BGCTRL: pcuint16 = pointer($04000008);
  REG_BG0CNT		: pcuint16 = pointer($4000008);
  REG_BG1CNT		: pcuint16 = pointer($400000A);
  REG_BG2CNT		: pcuint16 = pointer($400000C);
  REG_BG3CNT		: pcuint16 = pointer($400000E);
  
  REG_BGOFFSETS	: pcuint16 = pointer($4000010);
  REG_BG0HOFS		: pcuint16 = pointer($4000010);
  REG_BG0VOFS		: pcuint16 = pointer($4000012);
  REG_BG1HOFS		: pcuint16 = pointer($4000014);
  REG_BG1VOFS		: pcuint16 = pointer($4000016);
  REG_BG2HOFS		: pcuint16 = pointer($4000018);
  REG_BG2VOFS		: pcuint16 = pointer($400001A);
  REG_BG3HOFS		: pcuint16 = pointer($400001C);
  REG_BG3VOFS		: pcuint16 = pointer($400001E);
  
  REG_BG2PA		: pcint16 = pointer($4000020);
  REG_BG2PB		: pcint16 = pointer($4000022);
  REG_BG2PC		: pcint16 = pointer($4000024);
  REG_BG2PD		: pcint16 = pointer($4000026);
  
  REG_BG2X		: pcint32 = pointer($4000028);
  REG_BG2Y		: pcint32 = pointer($400002C);
  
  REG_BG3PA		: pcint16 = pointer($4000030);
  REG_BG3PB		: pcint16 = pointer($4000032);
  REG_BG3PC		: pcint16 = pointer($4000034);
  REG_BG3PD		: pcint16 = pointer($4000036);
  
  REG_BG3X		: pcint32 = pointer($4000038);
  REG_BG3Y		: pcint32 = pointer($400003C);

	BACKGROUND_SUB : Pbg_attribute = pointer($04001008);
  BG_OFFSET_SUB: Pbg_scroll = pointer($04001010);

function BG_MAP_RAM_SUB(base: cint): pcuint16; inline; 
function BG_TILE_RAM_SUB(base: cint): pcuint16; inline; 
function BG_BMP_RAM_SUB(base: cint): pcuint16; inline; 
function SCREEN_BASE_BLOCK_SUB(n: cint): pcuint16; inline;
function CHAR_BASE_BLOCK_SUB(n: cint): pcuint16; inline;


const
  BGCTRL_SUB		: pcuint16 = pointer($4001008);
  REG_BG0CNT_SUB		: pcuint16 = pointer($4001008);
  REG_BG1CNT_SUB		: pcuint16 = pointer($400100A);
  REG_BG2CNT_SUB		: pcuint16 = pointer($400100C);
  REG_BG3CNT_SUB		: pcuint16 = pointer($400100E);

  REG_BGOFFSETS_SUB	: pcuint16 = pointer($4001010);
  REG_BG0HOFS_SUB		: pcuint16 = pointer($4001010);
  REG_BG0VOFS_SUB		: pcuint16 = pointer($4001012);
  REG_BG1HOFS_SUB		: pcuint16 = pointer($4001014);
  REG_BG1VOFS_SUB		: pcuint16 = pointer($4001016);
  REG_BG2HOFS_SUB		: pcuint16 = pointer($4001018);
  REG_BG2VOFS_SUB		: pcuint16 = pointer($400101A);
  REG_BG3HOFS_SUB		: pcuint16 = pointer($400101C);
  REG_BG3VOFS_SUB		: pcuint16 = pointer($400101E);
  
  REG_BG2PA_SUB		: pcint16 = pointer($4001020);
  REG_BG2PB_SUB		: pcint16 = pointer($4001022);
  REG_BG2PC_SUB		: pcint16 = pointer($4001024);
  REG_BG2PD_SUB		: pcint16 = pointer($4001026);
  
  REG_BG2X_SUB		: pcint32 = pointer($4001028);
  REG_BG2Y_SUB		: pcint32 = pointer($400102C);
  
  REG_BG3PA_SUB		: pcint16 = pointer($4001030);
  REG_BG3PB_SUB		: pcint16 = pointer($4001032);
  REG_BG3PC_SUB		: pcint16 = pointer($4001034);
  REG_BG3PD_SUB		: pcint16 = pointer($4001036);
  
  REG_BG3X_SUB		: pcint32 = pointer($4001038);
  REG_BG3Y_SUB		: pcint32 = pointer($400103C);
  
type
  //background state
  TBgState = record
    angle: cint;
    centerX, centerY: cint32;
    scaleX, scaleY: cint32;
    scrollX, scrollY: cint32;
    size: cint;
    _type: cint;
    dirty: cbool;
  end;
  PBgState = ^TBgState;
  
var
  bgControl: array [0..7] of pcuint16; cvar; external;
  bgScrollTable: array [0..7] of Pbg_scroll; cvar; external;
  bgTransform: array [0..7] of Pbg_transform; cvar; external;
  bgState: array [0..7] of TBgState; cvar; external;


type
  BgType = integer;
const
  BgType_Text8bpp   = 0;  
  BgType_Text4bpp   = 1; 
  BgType_Rotation   = 2;
  BgType_ExRotation = 3;
  BgType_Bmp8       = 4;
  BgType_Bmp16      = 5;

type
  BgSize = integer;
const
  BgSize_R_128x128    : BgSize = (0 shl 14);
  BgSize_R_256x256    : BgSize = (1 shl 14);
  BgSize_R_512x512    : BgSize = (2 shl 14);
  BgSize_R_1024x1024  : BgSize = (3 shl 14);	 	         
  BgSize_T_256x256    : BgSize = (0 shl 14) or (1 shl 16);	         
  BgSize_T_512x256    : BgSize = (1 shl 14) or (1 shl 16);	        
  BgSize_T_256x512    : BgSize = (2 shl 14) or (1 shl 16);	         
  BgSize_T_512x512    : BgSize = (3 shl 14) or (1 shl 16);	 	         
  BgSize_ER_128x128   : BgSize = (0 shl 14) or (2 shl 16);	         
  BgSize_ER_256x256   : BgSize = (1 shl 14) or (2 shl 16);	         
  BgSize_ER_512x512   : BgSize = (2 shl 14) or (2 shl 16);	         
  BgSize_ER_1024x1024 : BgSize = (3 shl 14) or (2 shl 16);	 	         
  BgSize_B8_128x128   : BgSize = (0 shl 14) or (1 shl 7) or (3 shl 16);	         
  BgSize_B8_256x256   : BgSize = (1 shl 14) or (1 shl 7) or (3 shl 16);	         
  BgSize_B8_512x256   : BgSize = (2 shl 14) or (1 shl 7) or (3 shl 16);	         
  BgSize_B8_512x512   : BgSize = (3 shl 14) or (1 shl 7) or (3 shl 16);	         
  BgSize_B8_1024x512  : BgSize = (1 shl 14) or (3 shl 16);	         
  BgSize_B8_512x1024  : BgSize = (0 or (3 shl 16));	 	         
  BgSize_B16_128x128  : BgSize = (0 shl 14) or (1 shl 7) or (1 shl 2) or (4 shl 16);	         
  BgSize_B16_256x256  : BgSize = (1 shl 14) or (1 shl 7) or (1 shl 2) or (4 shl 16);	         
  BgSize_B16_512x256  : BgSize = (2 shl 14) or (1 shl 7) or (1 shl 2) or (4 shl 16);	         
  BgSize_B16_512x512  : BgSize = (3 shl 14) or (1 shl 7) or (1 shl 2) or (4 shl 16);

function bgIsText(id: cint): cbool;	cdecl; external; 
function bgInit_call(layer: cint; atype: BgType; size: BgSize; mapBase, tileBase: cint): cint;	cdecl; external; 
function bgInitSub_call(layer: cint; atype: BgType; size: BgSize; mapBase, tileBase: cint): cint;	cdecl; external;

procedure bgUpdate(); cdecl; external;

procedure bgSetRotate(id, angle: cint); inline;
procedure bgRotate(id, angle: cint); inline;
procedure bgSet(id, angle: cint; sx, sy, scrollX, scrollY, rotCenterX, rotCenterY: cint32); inline;
procedure bgSetRotateScale(id, angle: cint; sx, sy: cint32); inline;
procedure bgSetScale(id: cint; sx, sy: cint32); inline;
function bgInit(layer: cint; atype: BgType; size: BgSize; mapBase, tileBase: cint): cint; inline;
function bgInitSub(layer: cint; atype: BgType; size: BgSize; mapBase, tileBase: cint): cint; inline;
function bgSetControlBits(id: cint; bits: cuint16): pcuint16; inline;
procedure bgClearControlBits(id: cint; bits: cuint16); inline;
procedure bgWrapOn(id: cint); inline;
procedure bgWrapOff(id: cint); inline;
procedure bgSetPriority(id: cint; priority: cuint); inline;
procedure bgSetMapBase(id: cint; base: cuint); inline;
procedure bgSetTileBase(id: cint; base: cuint); inline;	
procedure bgSetScrollf(id: cint; x, y: cint32); inline;
procedure bgSetScroll(id, x, y: cint); inline;
procedure bgMosaicEnable(id: cint); inline;
procedure bgMosaicDisable(id: cint); inline;
procedure bgSetMosaic(dx, dy: cuint); inline;
procedure bgSetMosaicSub(dx, dy: cuint); inline;
function bgGetPriority(id: cint): cint; inline;
function bgGetMapBase(id: cint): cint; inline;
function bgGetTileBase(id: cint): cint; inline;
function bgGetMapPtr(id: cint): pcuint16; inline;
function bgGetGfxPtr(id: cint): pcuint16; inline;
procedure bgScrollf(id: cint; dx, dy: cint32); inline;
procedure bgScroll(id, dx, dy: cint); inline;
procedure bgShow(id: cint); inline;
procedure bgHide(id: cint); inline;
procedure bgSetCenterf(id: cint; x, y: cint32); inline;
procedure bgSetCenter(id, x, y: cint); inline;
procedure bgSetAffineMatrixScroll(id, hdx, vdx, hdy, vdy, scrollx, scrolly: cint); inline;

procedure bgExtPaletteEnable(); inline; 
procedure bgExtPaletteEnableSub(); inline; 
procedure bgExtPaletteDisable(); inline; 
procedure bgExtPaletteDisableSub(); inline; 

{$endif NDS_INTERFACE}

{$ifdef NDS_IMPLEMENTATION}
function BG_TILE_BASE(base: cint): cint; inline; 
begin 
  BG_TILE_BASE := ((base) shl 2);
end;

function BG_MAP_BASE(base: cint): cint; inline;  
begin
  BG_MAP_BASE := ((base) shl 8);
end;

function BG_BMP_BASE(base: cint): cint; inline;  
begin
  BG_BMP_BASE := ((base) shl 8);
end;

function BG_PRIORITY(n: cint): cint; inline;
begin
  BG_PRIORITY := (n);
end;

function TILE_PALETTE(n: cint): cint; inline;
begin
  TILE_PALETTE := ((n) shl 12);
end;

function BG_MAP_RAM(base: cint): pcuint16; inline;  
begin
  BG_MAP_RAM := pcuint16(((base) * $800) + $06000000);
end;

function BG_MAP_RAM_SUB(base: cint): pcuint16; inline; 
begin
  BG_MAP_RAM_SUB := pcuint16(((base) * $800) + $06200000);
end;


function BG_TILE_RAM(base: cint): pcuint16; inline; 
begin
  BG_TILE_RAM := pcuint16(((base) * $4000) + $06000000);
end;

function BG_TILE_RAM_SUB(base: cint): pcuint16; inline; 
begin
  BG_TILE_RAM_SUB := pcuint16(((base) * $4000) + $06200000);
end;


function BG_BMP_RAM(base: cint): pcuint16; inline;  
begin
  BG_BMP_RAM := pcuint16(((base) * $4000) + $06000000);
end;

function BG_BMP_RAM_SUB(base: cint): pcuint16; inline; 
begin
  BG_BMP_RAM_SUB := pcuint16(((base) * $4000) + $06200000);
end;

function CHAR_BASE_BLOCK(n: cint): pcuint16; inline;
begin
  CHAR_BASE_BLOCK := pcuint16((n * $4000)+ $06000000);
end;

function CHAR_BASE_BLOCK_SUB(n: cint): pcuint16; inline;
begin		
  CHAR_BASE_BLOCK_SUB := pcuint16((n * $4000)+ $06200000);
end;

function SCREEN_BASE_BLOCK(n: cint): pcuint16; inline;
begin		
  SCREEN_BASE_BLOCK := pcuint16((n * $800) + $06000000);
end;

function SCREEN_BASE_BLOCK_SUB(n: cint): pcuint16; inline;
begin	
  SCREEN_BASE_BLOCK_SUB := pcuint16((n * $800) + $06200000);
end;

procedure bgSetRotate(id, angle: cint); inline;
begin
  bgState[id].angle := angle;
  bgState[id].dirty := true;
end;

procedure bgRotate(id, angle: cint); inline;
begin
  sassert(not bgIsText(id), 'Cannot Rotate a Text Background');
  bgSetRotate(id, angle + bgState[id].angle);
end;

procedure bgSet(id, angle: cint; sx, sy, scrollX, scrollY, rotCenterX, rotCenterY: cint32); inline;
begin
  bgState[id].scaleX := sx;
  bgState[id].scaleY := sy;
  bgState[id].scrollX := scrollX;
  bgState[id].scrollY := scrollY;
  bgState[id].centerX := rotCenterX;
  bgState[id].centerY := rotCenterY;
  bgState[id].angle := angle;
  bgState[id].dirty := true;	 
end;

procedure bgSetRotateScale(id, angle: cint; sx, sy: cint32); inline;
begin
  bgState[id].scaleX := sx;
  bgState[id].scaleY := sy;
  bgState[id].angle := angle;
  bgState[id].dirty := true;
end;

procedure bgSetScale(id: cint; sx, sy: cint32); inline;
begin 
  sassert( not bgIsText(id), 'Cannot Scale a Text Background');
  bgState[id].scaleX := sx;
  bgState[id].scaleY := sy;
  bgState[id].dirty := true;
end;

function bgInit(layer: cint; atype: BgType; size: BgSize; mapBase, tileBase: cint): cint; inline;
begin
  sassert( (layer >= 0) and (layer <= 3), 'Only layers 0 - 3 are supported');
  sassert( (tileBase >= 0) and (tileBase <= 15), 'Background tile base is out of range');
  sassert( (mapBase >=0) and (mapBase <= 31), 'Background Map Base is out of range');
  sassert( (layer <> 0) or not video3DEnabled(), 'Background 0 is currently being used for 3D display');
  sassert( (layer > 1) or (atype = BgType_Text8bpp) or (atype = BgType_Text4bpp), 'Incorrect background type for mode');
  //sassert((size != BgSize_B8_512x1024 && size != BgSize_B8_1024x512) || videoGetMode() == 6, "Incorrect background type for mode");
  sassert( (tileBase = 0) or (atype < BgType_Bmp8), 'Tile base is unused for bitmaps.  Can be offset using mapBase * 16KB');
  sassert( ((mapBase = 0) or (atype <> BgType_Bmp8)) or ((size <> BgSize_B8_512x1024) and (size <> BgSize_B8_1024x512)), 'Large Bitmaps cannot be offset');
  result := bgInit_call(layer, atype, size, mapBase, tileBase);	 
end;

function bgInitSub(layer: cint; atype: BgType; size: BgSize; mapBase, tileBase: cint): cint; inline;
begin
  sassert( (layer >= 0) and (layer <= 3), 'Only layers 0 - 3 are supported');
  sassert( (tileBase >= 0) and (tileBase <= 15), 'Background tile base is out of range');
  sassert( (mapBase >=0) and (mapBase <= 31), 'Background Map Base is out of range');
  sassert( (layer > 1) or (atype = BgType_Text8bpp) or (atype = BgType_Text4bpp), 'Incorrect background type for mode');
  sassert( ((size <> BgSize_B8_512x1024) and (size <> BgSize_B8_1024x512)), 'Sub Display has no large Bitmaps');
  result := bgInitSub_call(layer, atype, size, mapBase, tileBase);
end;

function bgSetControlBits(id: cint; bits: cuint16): pcuint16; inline;
begin
	sassert( (id >= 0) and (id <= 7), 'bgSetControlBits(), id must be the number returned from bgInit or bgInitSub');
  bgControl[id]^ := bgControl[id]^ or bits;
  result := bgControl[id];
end;  
  
procedure bgClearControlBits(id: cint; bits: cuint16); inline;
begin
  bgControl[id]^ := bgControl[id]^ and not bits;	 
end;  

procedure bgWrapOn(id: cint); inline;
begin
  bgSetControlBits(id, BIT(13));
end;

procedure bgWrapOff(id: cint); inline;
begin
  bgClearControlBits(id, BIT(13));
end;

procedure bgSetPriority(id: cint; priority: cuint); inline;
begin
  sassert( (priority < 4), 'Priority must be less than 4');
  bgControl[id]^ := bgControl[id]^ and not 3;
  bgControl[id]^ := bgControl[id]^ or priority;	 	 
end;

procedure bgSetMapBase(id: cint; base: cuint); inline;
begin
  sassert( (base <= 31), 'Map base cannot exceed 31');
  bgControl[id]^ := bgControl[id]^ and not (31 shl MAP_BASE_SHIFT);
  bgControl[id]^ := bgControl[id]^ or (base shl MAP_BASE_SHIFT);
end;
    
procedure bgSetTileBase(id: cint; base: cuint); inline;	
begin
  sassert( (base <= 15), 'Tile base cannot exceed 15');
  bgControl[id]^ := bgControl[id]^ and not (15 shl TILE_BASE_SHIFT);
  bgControl[id]^ := bgControl[id]^ or (base shl TILE_BASE_SHIFT);
end;

procedure bgSetScrollf(id: cint; x, y: cint32); inline;
begin
  bgState[id].scrollX := x;
  bgState[id].scrollY := y;
  bgState[id].dirty := true;
end;

procedure bgSetScroll(id, x, y: cint); inline;
begin
  bgSetScrollf(id, x shl 8, y shl 8);
end;

procedure bgMosaicEnable(id: cint); inline;
begin
  bgControl[id]^ := bgControl[id]^ or BIT(6);
end;

procedure bgMosaicDisable(id: cint); inline;
begin
  bgControl[id]^ := bgControl[id]^ and not BIT(6);
end;

procedure bgSetMosaic(dx, dy: cuint); inline;
begin
  sassert( (dx < 16) and (dy < 16), 'Mosaic range is 0 to 15');
  mosaicShadow := (mosaicShadow and $ff00) or (dx or (dy shl 4));
  REG_MOSAIC^ := mosaicShadow;
end;

procedure bgSetMosaicSub(dx, dy: cuint); inline;
begin
  sassert( (dx < 16) and (dy < 16), 'Mosaic range is 0 to 15');
  mosaicShadowSub := (mosaicShadowSub and $ff00) or (dx or (dy shl 4));
  REG_MOSAIC_SUB^ := mosaicShadowSub;
end;



function bgGetPriority(id: cint): cint; inline;
begin
  result := bgControl[id]^ and 3;
end;

function bgGetMapBase(id: cint): cint; inline;
begin
  result := (bgControl[id]^ shr MAP_BASE_SHIFT) and 31;
end;


function bgGetTileBase(id: cint): cint; inline;
begin
  result := (bgControl[id]^ shr TILE_BASE_SHIFT) and 15;
end;

function bgGetMapPtr(id: cint): pcuint16; inline;
begin
  if (id < 4) then 
    result := pcuint16(BG_MAP_RAM(bgGetMapBase(id))) 
  else
    result := pcuint16(BG_MAP_RAM_SUB(bgGetMapBase(id)));
end;

function bgGetGfxPtr(id: cint): pcuint16; inline;
begin
  if(bgState[id]._type < integer(BgType_Bmp8)) then 
  begin
    if (id < 4) then 
      result := pcuint16(BG_TILE_RAM(bgGetTileBase(id))) 
    else 
      result := pcuint16(BG_TILE_RAM_SUB(bgGetTileBase(id)));	         
  end else	                 
  begin
    if (id < 4) then
      result := pointer(BG_GFX + $2000 * (bgGetMapBase(id))) 
    else 
      result := pointer(BG_GFX_SUB + $2000 * (bgGetMapBase(id)));
  end;
end;

procedure bgScrollf(id: cint; dx, dy: cint32); inline;
begin
  bgSetScrollf(id, bgState[id].scrollX + dx, bgState[id].scrollY + dy);
end;

procedure bgScroll(id, dx, dy: cint); inline;
begin
  bgScrollf(id, dx shl 8, dy shl 8);
end;

procedure bgShow(id: cint); inline;
begin
  if (id < 4) then
    videoBgEnable(id)
  else
    videoBgEnableSub(id and 3);
end;

procedure bgHide(id: cint); inline;
begin
  if (id < 4) then
    videoBgDisable(id)
  else
    videoBgDisableSub(id and 3);
end;

procedure bgSetCenterf(id: cint; x, y: cint32); inline;
begin
  sassert(not bgIsText(id), 'Text Backgrounds have no Center of Rotation');
  bgState[id].centerX := x;
  bgState[id].centerY := y;
  bgState[id].dirty := true;
end;

procedure bgSetCenter(id, x, y: cint); inline;
begin
  bgSetCenterf(id, x shl 8, y shl 8);
end;

procedure bgSetAffineMatrixScroll(id, hdx, vdx, hdy, vdy, scrollx, scrolly: cint); inline;
begin
  sassert(not bgIsText(id), 'Text Backgrounds have no affine matrix and scroll registers.');

  bgTransform[id]^.hdx := hdx;
  bgTransform[id]^.vdx := vdx;
  bgTransform[id]^.hdy := hdy;
  bgTransform[id]^.vdy := vdy;
  
  bgTransform[id]^.dx := scrollx;
  bgTransform[id]^.dy := scrolly;
  
  bgState[id].dirty := false;
end;

procedure bgExtPaletteEnable(); inline; 
begin 
  REG_DISPCNT^ := REG_DISPCNT^ or DISPLAY_BG_EXT_PALETTE; 
end;

procedure bgExtPaletteEnableSub(); inline; 
begin 
  REG_DISPCNT_SUB^ := REG_DISPCNT_SUB^ or DISPLAY_BG_EXT_PALETTE; 
end;

procedure bgExtPaletteDisable(); inline; 
begin 
  REG_DISPCNT^ := REG_DISPCNT^ and not DISPLAY_BG_EXT_PALETTE; 
end;

procedure bgExtPaletteDisableSub(); inline; 
begin 
  REG_DISPCNT_SUB^ := REG_DISPCNT_SUB^ and not DISPLAY_BG_EXT_PALETTE; 
end;

{$endif NDS_IMPLEMENTATION}