## DDOVERLAYFX

The DDOVERLAYFX structure passes override information to the IDirectDrawSurface3::UpdateOverlay method.

typedef struct _DDOVERLAYFX{

DWORD dwSize;

DWORD dwAlphaEdgeBlendBitDepth;

DWORD dwAlphaEdgeBlend;

DWORD dwReserved;

DWORD dwAlphaDestConstBitDepth;

union

{

DWORD dwAlphaDestConst;

LPDIRECTDRAWSURFACE lpDDSAlphaDest;

};

DWORD dwAlphaSrcConstBitDepth;

union

{

DWORD dwAlphaSrcConst;

LPDIRECTDRAWSURFACE lpDDSAlphaSrc;

};

DDCOLORKEY dckDestColorkey;

DDCOLORKEY dckSrcColorkey;

DWORD dwDDFX;

DWORD dwFlags;

} DDOVERLAYFX,FAR *LPDDOVERLAYFX;

##### Members

dwSize
  Size of the structure, in bytes. This members must be initialized before the structure is used.
dwAlphaEdgeBlendBitDepth
  Bit depth used to specify the constant for an alpha edge blend.
dwAlphaEdgeBlend
  Constant to use as the alpha for an edge blend.
dwReserved
  Reserved for future use.
dwAlphaDestConstBitDepth
  Bit depth used to specify the alpha constant for a destination.
dwAlphaDestConst
  Constant to use as the alpha channel for a destination.
lpDDSAlphaDest
  Address of a surface to use as the alpha channel for a destination.
dwAlphaSrcConstBitDepth
  Bit depth used to specify the alpha constant for a source.
dwAlphaSrcConst
  Constant to use as the alpha channel for a source.
lpDDSAlphaSrc
  Address of a surface to use as the alpha channel for a source.
dckDestColorkey
  Destination color key override.
dckSrcColorkey
  Source color key override.
dwDDFX
  Overlay FX flags.

  DDOVERFX_ARITHSTRETCHY
  | If stretching, use arithmetic stretching along the y-axis for this overlay.
  DDOVERFX_MIRRORLEFTRIGHT
  | Mirror the overlay around the vertical axis.
  DDOVERFX_MIRRORUPDOWN
  | Mirror the overlay around the horizontal axis.

dwFlags
  This member is currently not used and must be set to 0.