ForegroundIdleProc callback function

Article
03/30/2018

An application-defined or library-defined callback function used with the SetWindowsHookEx function. The system calls this function whenever the foreground thread is about to become idle.

The HOOKPROC type defines a pointer to this callback function. ForegroundIdleProc is a placeholder for the application-defined or library-defined function name.

Syntax

DWORD CALLBACK ForegroundIdleProc(
  _In_ int   code,
       DWORD wParam,
       LONG  lParam
);

Parameters

code [in]
Type: int

If code is HC_ACTION, the hook procedure must process the message. If code is less than zero, the hook procedure must pass the message to the CallNextHookEx function without further processing and should return the value returned by CallNextHookEx.
wParam
Type: DWORD

This parameter is not used.
lParam
Type: LONG

This parameter is not used.

Return value

Type: ****

Type: DWORD

If code is less than zero, the hook procedure must return the value returned by CallNextHookEx.

If code is greater than or equal to zero, it is highly recommended that you call CallNextHookEx and return the value it returns; otherwise, other applications that have installed WH_FOREGROUNDIDLE hooks will not receive hook notifications and may behave incorrectly as a result. If the hook procedure does not call CallNextHookEx, the return value should be zero.

Remarks

An application installs this hook procedure by specifying the WH_FOREGROUNDIDLE hook type and the pointer to the hook procedure in a call to the SetWindowsHookEx function.

While processing this callback function, avoid calling any functions that retrieve window messages from the calling thread's message queue. This includes GetMessage, PeekMessage, modal dialog box, and COM functions. Calling such functions may result in the thread not returning from GetMessage or WaitMessage when there are messages in the calling thread's message queue.

Requirements

Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	Winuser.h (include Windows.h)