hdc (HDC) - input

Device context handle.

pInstance (PVOID) - input

Pointer to instance data.

lFunction (ULONG) - input

High-order WORD=flags; low-order WORD=NGreQueryClipRegion.

rc (HRGN) - returns

This function returns the handle of the clip region:

hrgn

Region handle
NULL
Null handle (no region selected)
HRGN_ERROR
Error
Possible Errors Detected: When an error is detected, the handling routine must call WinSetErrorInfo to post the condition. Error codes for conditions that the handling routine is expected to check include:

PMERR_HDC_BUSY PMERR_INV_HDC

Refer to the "Error Explanations" section in the Presentation Manager Programming Reference for further explanation.