CONST_DDOVERFLAGS
The flags in the CONST_DDOVERFLAGS enumeration are used by the flags member of the DirectDrawSurface7.UpdateOverlay method to modify the visual attributes on an overlay. 
Enum CONST_DDOVERFLAGS
    DDOVER_ADDDIRTYRECT             = 32768
    DDOVER_ALPHADEST                = 1
    DDOVER_ALPHADESTCONSTOVERRIDE   = 2
    DDOVER_ALPHADESTNEG             = 4
    DDOVER_ALPHADESTSURFACEOVERRIDE = 8
    DDOVER_ALPHAEDGEBLEND           = 16 
    DDOVER_ALPHASRC                 = 32
    DDOVER_ALPHASRCCONSTOVERRIDE    = 64
    DDOVER_ALPHASRCNEG              = 128
    DDOVER_ALPHASRCSURFACEOVERRIDE  = 256
    DDOVER_ARGBSCALEFACTORS         = 33554432
    DDOVER_AUTOFLIP                 = 1048576 
    DDOVER_BOB                      = 2097152 
    DDOVER_DDFX                     = 524288
    DDOVER_DEGRADEARGBSCALING       = 67108864
    DDOVER_HIDE                     = 512
    DDOVER_INTERLEAVED              = 8388608
    DDOVER_KEYDEST                  = 1024
    DDOVER_KEYDESTOVERRIDE          = 2048
    DDOVER_KEYSRC                   = 4096
    DDOVER_KEYSRCOVERRIDE           = 8192
    DDOVER_OVERRIDEBOBWEAVE         = 4194304
    DDOVER_REFRESHALL               = 131072
    DDOVER_REFRESHDIRTYRECTS        = 65536
    DDOVER_SHOW                     = 16384
End Enum
- DDOVER_ADDDIRTYRECT
- Adds a dirty rectangle to an emulated overlay surface. 
- DDOVER_ALPHADEST
- Obsolete.
- DDOVER_ALPHADESTCONSTOVERRIDE
- Uses the lAlphaDestConst member of the DDOVERLAYFX type as the destination  for this overlay. 
- DDOVER_ALPHADESTNEG
- The destination surface becomes more transparent as the alpha value increases (0 is opaque). 
- DDOVER_ALPHADESTSURFACEOVERRIDE
- Uses the lpDDSAlphaDest member of the DDOVERLAYFX type as the  destination for this overlay. 
- DDOVER_ALPHAEDGEBLEND
- Uses the lAlphaEdgeBlend member of the DDOVERLAYFX type as the  for the edges of the image that border the  colors. 
- DDOVER_ALPHASRC 
- Uses either the alpha information in pixel format or the  surface attached to the source surface as the source  for this overlay. 
- DDOVER_ALPHASRCCONSTOVERRIDE 
- Uses the lAlphaSrcConst member of the DDOVERLAYFX type as the source  for this overlay. 
- DDOVER_ALPHASRCNEG
- The source surface becomes more transparent as the alpha value increases (0 is opaque). 
- DDOVER_ALPHASRCSURFACEOVERRIDE
- Uses the lpDDSAlphaSrc member of the DDOVERLAYFX structure as the  source for this overlay.
- DDOVER_ARGBSCALEFACTORS
- New for DirectX 7.0. Overlay FX structure contains valid ARGB scaling factors.
- DDOVER_AUTOFLIP
- Automatically flips to the next surface in the flip chain each time a video port VSYNC occurs.
- DDOVER_BOB
- Displays each  of the interlaced video stream individually without causing any artifacts.
- DDOVER_DDFX
- When calling the DirectDrawSurface7.UpdateOverlayFx, setting this flag uses the flags set in the ddoverfx parameter to define special overlay effects. This flag must be set, or the ddoverfx parameter is ignored.
- DDOVER_DEGRADEARGBSCALING
- New for DirectX 7.0. ARGB scaling factors can be degraded to fit driver capabilities.
- DDOVER_HIDE 
- Turns off this overlay. 
- DDOVER_INTERLEAVED
- The surface memory is composed of interleaved fields.
- DDOVER_KEYDEST
- Uses the  associated with the destination surface. 
- DDOVER_KEYDESTOVERRIDE
- Uses the dckDestColorkey member of the DDOVERLAYFX type as the  for the destination surface. 
- DDOVER_KEYSRC 
- Uses the  associated with the source surface. 
- DDOVER_KEYSRCOVERRIDE
- Uses the dckSrcColorkey member of the DDOVERLAYFX type as the  for the source surface.
- DDOVER_OVERRIDEBOBWEAVE 
- Bob and weave decisions should not be overridden by other interfaces.
- DDOVER_REFRESHALL
- Redraws the entire surface on an emulated overlayed surface.
- DDOVER_REFRESHDIRTYRECTS
- Redraws all dirty rectangles on an emulated overlayed surface.
- DDOVER_SHOW
- Turns on this overlay.