WM_MBUTTONDOWN

The WM_MBUTTONDOWN message is posted when the user presses the middle 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.

WM_MBUTTONDOWN 
fwKeys = wParam;        // key flags 
xPos = LOWORD(lParam);  // horizontal position of cursor 
yPos = HIWORD(lParam);  // vertical position of cursor 
 

Parameters

fwKeys

Value of wParam. Indicates whether various virtual keys are down. This parameter can be any combination of the following values:

Value	Description
MK_CONTROL	Set if the ctrl key is down.
MK_LBUTTON	Set if the left mouse button is down.
MK_MBUTTON	Set if the middle mouse button is down.
MK_RBUTTON	Set if the right mouse button is down.
MK_SHIFT	Set if the shift key is down.

xPos

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

yPos

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

Return Values

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

Remarks

An application can use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in winuser.h.

See Also

Mouse Input Overview, Mouse Input Messages, GetCapture, MAKEPOINTS, POINTS, SetCapture, WM_MBUTTONDBLCLK, WM_MBUTTONUP