ShellProc

The ShellProc hook procedure is an application-defined or library-defined callback function used with the SetWindowsHookEx function. The function receives notifications of shell events from the system.

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

LRESULT CALLBACK ShellProc(
  int nCode,      // hook code
  WPARAM wParam,  // event-specific information
  LPARAM lParam   // event-specific information
);
 

Parameters

nCode

Specifies the hook code. This parameter can be one of the following values.

Value	Meaning
HSHELL_ACCESSIBILITYSTATE	Windows NT 5.0 and later: The accessibility state has changed.
HSHELL_ACTIVATESHELLWINDOW	The shell should activate its main window.
HSHELL_GETMINRECT	A window is being minimized or maximized. The system needs the coordinates of the minimized rectangle for the window.
HSHELL_LANGUAGE	Keyboard language was changed or a new keyboard layout was loaded.
HSHELL_REDRAW	The title of a window in the task bar has been redrawn.
HSHELL_TASKMAN	The user has selected the task list. A shell application that provides a task list should return TRUE to prevent Windows from starting its task list.
HSHELL_WINDOWACTIVATED	The activation has changed to a different top-level, unowned window.
HSHELL_WINDOWCREATED	A top-level, unowned window has been created. The window exists when the system calls a ShellProc function.
HSHELL_WINDOWDESTROYED	A top-level, unowned window is about to be destroyed. The window still exists when the system calls a ShellProc function.

If nCode 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

The value depends on the value of the nCode parameter, as shown in the following table.

nCode	wParam
HSHELL_ACCESSIBILITYSTATE	Indicates which accessibility feature has changed state. This value is one of the following: ACCESS_FILTERKEYS, ACCESS_MOUSEKEYS, or ACCESS_STICKYKEYS.
HSHELL_GETMINRECT	Handle to the minimized or maximized window.
HSHELL_LANGUAGE	Handle to the window.
HSHELL_REDRAW	Handle to the redrawn window.
HSHELL_WINDOWACTIVATED	Handle to the activated window.
HSHELL_WINDOWCREATED	Handle to the created window.
HSHELL_WINDOWDESTROYED	Handle to the destroyed window.

lParam

The value depends on the value of the nCode parameter, as shown in the following table.

nCode	lParam
HSHELL_GETMINRECT	Pointer to a RECT structure.
HSHELL_LANGUAGE	Handle to a keyboard layout.
HSHELL_REDRAW	The value is TRUE if the window is flashing, or FALSE otherwise.
HSHELL_WINDOWACTIVATED	The value is TRUE if the window is in full-screen mode, or FALSE otherwise.

Return Values

The return value should be zero.

Remarks

Install this hook procedure by specifying the WH_SHELL hook type and the address of the hook procedure in a call to the SetWindowsHookEx function.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in winuser.h.
  Import Library: User-defined.

See Also

Hooks Overview, Hook Functions, CallNextHookEx, SendMessage, SetWindowsHookEx