The WM_MBUTTONUP message is posted when the user releases 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_MBUTTONUP
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_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.
An application can use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.
See Also
GetCapture, MAKEPOINTS, POINTS, SetCapture, WM_MBUTTONDBLCLK, WM_MBUTTONDOWN