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#define INCL_GPIPRIMITIVES
 
BOOL GpiSetBackMix(hps, lMixMode)
HPS hps;          /* presentation-space handle */
LONG lMixMode;    /* background-mix mode       */
 
The GpiSetBackMix function sets the current background-mix mode for all
primitive types. The background-mix mode specifies how the background color
is combined with colors in underlying primitives. The available
background-mix modes depend on the device associated with the presentation
space, but all devices support the BM_LEAVEALONE and BM_OVERPAINT mix modes.
If the mix mode specified by lMixMode is not supported, the function uses
FM_LEAVEALONE instead. The DevQueryCaps function can be used to determine
which mix modes are supported.
 
If the attribute mode is AM_PRESERVE, the function saves the previous
background-mix mode on the attribute stack when it sets the new mode. The
previous background-mix mode can be retrieved by using the GpiPop function.
 
Parameter  Description
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hps        Identifies the presentation space.
 
lMixMode   Specifies the background-mix mode. It can be one of the following
           values:
 
           Value          Meaning
           ─────────────────────────────────────────────────────────────────
           BM_DEFAULT     The default value (BM_LEAVEALONE).
 
           BM_LEAVEALONE  The background color is ignored. The existing
                          color remains unchanged.
 
           BM_OR          The individual pel colors are combined using the
                          OR operator.
 
           BM_OVERPAINT   The background color replaces the existing color.
 
           BM_XOR         The individual pel colors are combined using the
                          XOR operator.
 
Return Value
 
The return value is GPI_OK if the function is successful or GPI_ERROR if an
error occurred.
 
Errors
 
Use the WinGetLastError function to retrieve the error value, which may be
the following:
 
     PMERR_INV_BACKGROUND_MIX_ATTR
     PMERR_INV_HPS
     PMERR_PS_BUSY
 
Comments
 
The background-mix mode is used when drawing areas, images, markers, and
characters. For areas and images, the mix mode applies to pels that are not
set by the shading pattern. For markers, the mix mode applies to pels not
set by the marker pattern. For characters, the mix mode applies to pels not
set by the character pattern.
 
See Also
 
DevQueryCaps, GpiPop, GpiSetBackColor, WinGetLastError
 
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