Used by UpdateLayeredWindowIndirect to provide position, size, shape, content, and translucency information for a layered window.

Syntax

typedef struct tagUPDATELAYEREDWINDOWINFO {
    DWORD cbSize;
    HDC hdcDst;
    const POINT *pptDst;
    const SIZE *psize;
    HDC hdcSrc;
    const POINT *pptSrc;
    COLORREF crKey;
    const BLENDFUNCTION *pblend;
    DWORD dwFlags;
    const RECT *prcDirty;
} UPDATELAYEREDWINDOWINFO, *PUPDATELAYEREDWINDOWINFO;

Members

cbSize

Size, in bytes, of this structure.

hdcDst

Handle to a device context (DC) for the screen. This handle is obtained by specifying NULL in this member when calling UpdateLayeredWindowIndirect. The handle is used for palette color matching when the window contents are updated. If hdcDst is NULL, the default palette is used.

If hdcSrc is NULL, hdcDst must be NULL.

pptDst

Pointer to a POINT structure that specifies the new screen position of the layered window. If the new position is unchanged from the current position, pptDst can be NULL.

psize

Pointer to a SIZE structure that specifies the new size of the layered window. If the size of the window will not change, this parameter can be NULL. If hdcSrc is NULL, psize must be NULL.

hdcSrc

Handle to the DC for the surface that defines the layered window. This handle can be obtained by calling the CreateCompatibleDC function. If the shape and visual context of the window will not change, hdcSrc can be NULL.

pptSrc

Pointer to a POINT structure that specifies the location of the layer in the device context. If hdcSrc is NULL, pptSrc should be NULL.

crKey

COLORREF structure that specifies the color key to be used when composing the layered window. To generate a COLORREF, use the RGB macro.

pblend

Pointer to a BLENDFUNCTION structure that specifies the transparency value to be used when composing the layered window.

dwFlags

This parameter can be one of the following values.

ULW_ALPHA

Use pblend as the blend function. If the display mode is 256 colors or less, the effect of this value is the same as the effect of ULW_OPAQUE.

ULW_COLORKEY

Use crKey as the transparency color.

ULW_OPAQUE

Draw an opaque layered window.

If hdcSrc is NULL, dwFlags should be zero.

prcDirty

Pointer to a RECT structure that specifies the area to be updated. This parameter can be NULL. If it is non-NULL, only the area in this rectangle is updated from the source DC.

Structure Information

Header	Declared in Winuser.h, include Windows.h
Minimum operating systems	Windows Vista

See Also

UpdateLayeredWindow, Layered Windows