GreSelectClipRegion

GreSelectClipRegion specifies the region to be used for clipping.

This function can be hooked by the presentation driver.

Simulation support: This function is simulated by a handling routine in the graphics engine.

Syntax

GreSelectClipRegion(hdc, hrgn, phrgnOld, pInstance, lFunction)

Parameters

hdc (HDC) - input: Device context handle.
hrgn (HRGN) - input: Region handle.; When NULL, the clip region is set to clipping (the initial state).
phrgnOld (PHRGN) - output: Pointer to previously selected region handle. If this is a NULL handle, there was no clip region.
pInstance (PVOID) - input: Pointer to instance data.
lFunction (ULONG) - input: High-order WORD=flags; low-order WORD=NGreSelectClipRegion.

Return Code

rc (LONG) - returns

Return codes.

This function returns an integer (lComplexity) indicating the complexity of the DC region:

RGN_ERROR Error
RGN_NULL Null region
RGN_RECT Rectangular region
RGN_COMPLEX Complex region (more than 1 rectangle)

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_DEV_FUNC_NOT_INSTALLED
PMERR_HDC_BUSY
PMERR_HRGN_BUSY
PMERR_INSUFFICIENT_MEMORY
PMERR_INV_COORDINATE
PMERR_INV_HDC
PMERR_INV_HRGN
PMERR_INV_IN_AREA
PMERR_INV_IN_PATH
PMERR_INV_RECT
PMERR_INV_REGION_CONTROL
PMERR_REGION_IS_CLIP_REGION

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

Remarks

A region can only be selected by one DC at a time. As soon as a region is selected, operations that reference its handle are invalid. The coordinates of the region are in device coordinates within the DC. Clipping is inclusive at the left and bottom boundaries, exclusive at the right and top boundaries. Functions that modify the clipping region also modify the region when its handle is returned by a subsequent GreSelectClipRegion.

GreSelectClipRegion passes the handle of the previously selected clip region back to the calling routine at the location addressed by phrgnOld. If this handle is not NULL, the calling routine is responsible for deleting the previous clip region. If the default clip region is in use when GreSelectClipRegion is called, a null region handle is returned.

Note: The clip region should be deleted whether it was created explicitly, or in a call to GreIntersectClipRectangle or GreExcludeClipRectangle.

Declaration

#define INCL_GRE_CLIP
#include <os2.h>

HDC      hdc;        /*  Device context handle. */
HRGN     hrgn;       /*  Region handle. */
PHRGN    phrgnOld;
PVOID    pInstance;  /*  Pointer to instance data. */
ULONG    lFunction;
LONG     rc;         /*  Return codes. */

rc = GreSelectClipRegion(hdc, hrgn, phrgnOld, pInstance, lFunction);