[This is preliminary documentation and is subject to change.]

The LowLevelMouseProc hook procedure is an application-defined or library-defined callback function used with the SetWindowsHookEx function. The system call this function every time a new mouse input event is about to be posted into a thread input queue. The mouse input can come from the local mouse driver or from calls to the mouse_event function. If the input comes from a call to mouse_event, the input was "injected". However, the WH_MOUSE_LL hook is not injected into another process. Instead, the context switches back to the process that installed the hook and it is called in its original context. Then the context switches back to the application that generated the event.

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

Namespace: Tools.DevicesT
Assembly: Tools.Win (in Tools.Win.dll) Version: 1.5.3.38916 (1.5.3.38916)

Syntax

C#
protected override IntPtr HookProc(
	int nCode,
	IntPtr wParam,
	IntPtr lParam
)
Visual Basic
Protected Overrides Function HookProc ( _
	nCode As Integer, _
	wParam As IntPtr, _
	lParam As IntPtr _
) As IntPtr
Visual C++
protected:
virtual IntPtr HookProc(
	int nCode, 
	IntPtr wParam, 
	IntPtr lParam
) override
F#
abstract HookProc : 
        nCode:int * 
        wParam:IntPtr * 
        lParam:IntPtr -> IntPtr 
override HookProc : 
        nCode:int * 
        wParam:IntPtr * 
        lParam:IntPtr -> IntPtr
JScript
protected override function HookProc(
	nCode : int, 
	wParam : IntPtr, 
	lParam : IntPtr
) : IntPtr

Parameters

nCode
Type: System..::..Int32
Specifies a code the hook procedure uses to determine how to process the message. If nCode is less than zero, the hook procedure must pass the message to the CallNextHook(Int32, IntPtr, IntPtr) function without further processing and should return the value returned by CallNextHook(Int32, IntPtr, IntPtr).
wParam
Type: System..::..IntPtr
Specifies the identifier of the mouse message. This parameter can be one of the following messages: WM_LBUTTONDOWN, WM_LBUTTONUP, WM_MOUSEMOVE, WM_MOUSEWHEEL, WM_MOUSEHWHEEL, WM_RBUTTONDOWN, or WM_RBUTTONUP.
lParam
Type: System..::..IntPtr
[in] Pointer to an MSLLHOOKSTRUCT structure.

Return Value

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

If nCode is greater than or equal to zero, and the hook procedure did not process the message, it is highly recommended that you call CallNextHookEx and return the value it returns; otherwise, other applications that have installed WH_MOUSE_LL hooks will not receive hook notifications and may behave incorrectly as a result. If the hook procedure processed the message, it may return a nonzero value to prevent the system from passing the message to the rest of the hook chain or the target window procedure.

See Also