The WM_LBUTTONUP message is posted when the user releases the left mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.

A window receives this message through its WindowProc function.

Syntax

WM_LBUTTONUP

    WPARAM wParam
    LPARAM lParam;
    

Parameters

wParam

Indicates whether various virtual keys are down. This parameter can be one or more of the following values.

MK_CONTROL

The CTRL key is down.

MK_MBUTTON

The middle mouse button is down.

MK_RBUTTON

The right mouse button is down.

MK_SHIFT

The SHIFT key is down.

MK_XBUTTON1

Windows 2000/XP: The first X button is down.

MK_XBUTTON2

Windows 2000/XP: The second X button is down.

lParam

The low-order word specifies the x-coordinate of the cursor. The coordinate is relative to the upper-left corner of the client area.

The high-order word specifies the y-coordinate of the cursor. The coordinate is relative to the upper-left corner of the client area.

Return Value

If an application processes this message, it should return zero.

Remarks

Use the following code to obtain the horizontal and vertical position:

xPos = GET_X_LPARAM(lParam); 
yPos = GET_Y_LPARAM(lParam); 

You can also use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.

Notification Requirements

Minimum DLL Version	None
Header	Declared in Winuser.h, include Windows.h
Minimum operating systems	Windows 95, Windows NT 3.1

See Also

Mouse Input Overview, GET_X_LPARAM, GET_Y_LPARAM, GetCapture, SetCapture, MAKEPOINTS, POINTS, WM_LBUTTONDBLCLK, WM_LBUTTONDOWN