GreRectVisible

GreRectVisible checks whether any part of the given rectangle is visible within the DC region. The DC region is the intersection of the application clipping and the window 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

GreRectVisible(hdc, prclRect, pInstance, lFunction)

Parameters

hdc (HDC) - input

Device context handle.

prclRect (PRECTL) - input

Pointer to rectangle in world or screen coordinates. RECTL structure:

xLeft Minimum x-coordinate of rectangle
yBottom Minimum y-coordinate
xRight Maximum x-coordinate of rectangle
yTop Maximum y-coordinate

pInstance (PVOID) - input: Pointer to instance data.
lFunction (ULONG) - input: High-order WORD=flags; low-order WORD=NGreRectVisible.

Return Code

rc (LONG) - returns

Return codes.

This function returns an integer (lVisible) indicating the visibility of the rectangle.

RVIS_ERROR Error
RVIS_INVISIBLE Not visible
RVIS_PARTIAL Partially visible
RVIS_VISIBLE All visible

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_COORDINATE_OVERFLOW
PMERR_DEV_FUNC_NOT_INSTALLED
PMERR_HDC_BUSY
PMERR_INV_COORD_SPACE
PMERR_INV_COORDINATE
PMERR_INV_HDC
PMERR_INV_LENGTH_OR_COUNT
PMERR_INV_RECT

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

Declaration

#define INCL_GRE_CLIP
#include <os2.h>

HDC       hdc;        /*  Device context handle. */
PRECTL    prclRect;   /*  Pointer to rectangle in world or screen coordinates. RECTL structure: */
PVOID     pInstance;  /*  Pointer to instance data. */
ULONG     lFunction;  /*  High-order WORD=flags; low-order WORD=NGreRectVisible. */
LONG      rc;         /*  Return codes. */

rc = GreRectVisible(hdc, prclRect, pInstance, lFunction);