ExtSelectClipRgn info Overview Group

The ExtSelectClipRgn function combines the specified region with the current clipping region by using the specified mode.

int ExtSelectClipRgn(

Parameters

hdc

Identifies the device context.

hrgn

Identifies the region to be selected. This handle can only be NULL when the RGN_COPY mode is specified.

fnMode

Specifies the operation to be performed. It must be one of the following values:

Value	Meaning
RGN_AND	The new clipping region combines the overlapping areas of the current clipping region and the region identified by hrgn.
RGN_COPY	The new clipping region is a copy of the region identified by hrgn. This is identical to SelectClipRgn. If the region identified by hrgn is NULL, the new clipping region is the default clipping region (the default clipping region is a null region).
RGN_DIFF	The new clipping region combines the areas of the current clipping region with those areas excluded from the region identified by hrgn.
RGN_OR	The new clipping region combines the current clipping region and the region identified by hrgn.
RGN_XOR	The new clipping region combines the current clipping region and the region identified by hrgn but excludes any overlapping areas.

The return value specifies the new clipping region’s complexity; it can be any one of the following values:

Value	Meaning
NULLREGION	Region is empty.
SIMPLEREGION	Region is a single rectangle.
COMPLEXREGION	Region is more than one rectangle.
ERROR	An error occurred.

If an error occurs when this function is called, the previous clipping region for the specified device context is not affected.

The ExtSelectClipRgn function assumes that the coordinates for the specified region are specified in device units.

Only a copy of the region identified by the hrgn parameter is used. The region itself can be reused after this call or it can be deleted.