WM_MBUTTONDOWN
fwKeys = wParam; /* key flags */
xPos = LOWORD(lParam); /* horizontal position of cursor */
yPos = HIWORD(lParam); /* vertical position of cursor */The WM_MBUTTONDOWN message is sent when the user presses the middle mouse button.
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 CTRL key is down. |
| MK_LBUTTON | Set if left button is down. |
| MK_RBUTTON | Set if right button is down. |
| MK_SHIFT | Set if 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 window.
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 window.
An application should return zero if it processes this message.