WinQueryWindowPtr
This function retrieves a pointer value from the memory of the reserved window word.
Syntax
WinQueryWindowPtr(hwnd, index)
Parameters
- hwnd (HWND) - Input
- Window handle which has the pointer to retrieve.
- index (LONG) - Input
- Zero-based index of the pointer value to retrieve.
- The units of index are bytes. Valid values are zero through (cbWindowData - 4), where cbWindowData is the parameter in WinRegisterClass that specifies the number of bytes available for application-defined storage.
- The value QWP_PFNWP can be used for the address of the window's window procedure.
Returns
- pRet (PVOID) - returns
- NULL Error occurred.
- Other Pointer value.
Parameters
- hwnd (HWND) - Input
- Window handle which has the pointer to retrieve.
- index (LONG) - Input
- Zero-based index of the pointer value to retrieve.
- The units of index are bytes. Valid values are zero through (cbWindowData - 4), where cbWindowData is the parameter in WinRegisterClass that specifies the number of bytes available for application-defined storage.
- The value QWP_PFNWP can be used for the address of the window's window procedure.
- pRet (PVOID) - returns
- NULL Error occurred.
- Other Pointer value.
Remarks
The index parameter is valid only if all of the bytes referenced are within the reserved memory.
Errors
Possible returns from WinGetLastError:
- PMERR_INVALID_HWND (0x1001) An invalid window handle was specified.
- PMERR_PARAMETER_OUT_OF_RANGE (0x1003) The value of a parameter was not within the defined valid range for that parameter.
Example Code
#define INCL_WINWINDOWMGR /* Or use INCL_WIN, INCL_PM, */ #include <os2.h> HWND hwnd; /* Window handle which has the pointer to retrieve. */ LONG index; /* Zero-based index of the pointer value to retrieve. */ PVOID pRet; /* Pointer value. */ pRet = WinQueryWindowPtr(hwnd, index);
This function retrieves a pointer value from the memory of the reserved window word.
MyWindowProc(HWND hwnd, ULONG msg, MPARAM mp1, MPARAM mp2)
{
MYINSTANCEDATA *InstanceData; /* application defined structure */
switch (msg) {
case WM_CREATE:
DosAllocMem(&InstanceData, sizeof(MYINSTANCEDATA), fALLOC);
/* WindowProcedure initializes instance data for this window */
.
.
/* set pointer to instance in window words */
WinSetWindowPtr(hwnd, 0, InstanceData);
break;
case WM_USER + 1: /* application defined message */
/* Window procedure retrieves instance data to */
/* process this message */
InstanceData = WinQueryWindowPtr(hwnd, 0);
.
.
break;
.
.