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);