The WM_RBUTTONDOWN message is posted when the user presses the right 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_RBUTTONDOWN fwKeys = wParam; // key flags xPos = LOWORD(lParam); // horizontal position of cursor yPos = HIWORD(lParam); // vertical position of cursor
| 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. | 
If an application processes this message, it should return zero.
An application can use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.
GetCapture, MAKEPOINTS, POINTS, SetCapture, WM_RBUTTONDBLCLK, WM_RBUTTONUP