The WM_MBUTTONDBLCLK message is posted when the user double-clicks 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_MBUTTONDBLCLK
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
Only windows that have the CS_DBLCLKS style can receive WM_MBUTTONDBLCLK messages, which Windows generates whenever the user presses, releases, and again presses the middle mouse button within the system's double-click time limit. Double-clicking the middle mouse button actually generates four messages: WM_MBUTTONDOWN, WM_MBUTTONUP, WM_MBUTTONDBLCLK, and WM_MBUTTONUP again.
An application can use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.
See Also
GetCapture, GetDoubleClickTime, MAKEPOINTS, POINTS, SetCapture, SetDoubleClickTime, WM_MBUTTONDOWN, WM_MBUTTONUP