DDOVERLAYFX structure (ddraw.h)

Article
11/23/2021

The DDOVERLAYFX structure passes overlay information to the IDirectDrawSurface7::UpdateOverlay method.

Syntax

typedef struct _DDOVERLAYFX {
  DWORD      dwSize;
  DWORD      dwAlphaEdgeBlendBitDepth;
  DWORD      dwAlphaEdgeBlend;
  DWORD      dwReserved;
  DWORD      dwAlphaDestConstBitDepth;
#if ...
  union {
    DWORD               dwAlphaDestConst;
    LPDIRECTDRAWSURFACE lpDDSAlphaDest;
  } DUMMYUNIONNAMEN;
  DWORD      dwAlphaSrcConstBitDepth;
#else
  union {
    DWORD               dwAlphaSrcConst;
    LPDIRECTDRAWSURFACE lpDDSAlphaSrc;
  } DUMMYUNIONNAMEN;
#endif
  DDCOLORKEY dckDestColorkey;
  DDCOLORKEY dckSrcColorkey;
  DWORD      dwDDFX;
  DWORD      dwFlags;
} DDOVERLAYFX;

Members

dwSize

Size of the structure, in bytes. This member 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

dwAlphaDestConstBitDepth

Bit depth used to specify the alpha constant for a destination.

DUMMYUNIONNAMEN

See Remarks.

DUMMYUNIONNAMEN.dwAlphaDestConst

Constant to use as the alpha channel for a destination.

DUMMYUNIONNAMEN.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.

DUMMYUNIONNAMEN.dwAlphaSrcConst

Constant to use as the alpha channel for a source.

DUMMYUNIONNAMEN.lpDDSAlphaSrc

Address of a surface to use as the alpha channel for a source.

dckDestColorkey

Destination color key for the overlay.

dckSrcColorkey

Source color key for the overlay.

dwDDFX

The following flags that specify overlay effects.

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

Currently not used and must be set to 0.

Remarks

The unions in this structure have been updated to work with compilers that do not support nameless unions. If your compiler does not support nameless unions, define the NONAMELESSUNION token before including the Ddraw.h header file.

Requirements

Requirement	Value
Header	ddraw.h

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