WMRBUTTONDOWN

WMRBUTTONDOWN is often encountered as a mnemonic or alias in discussions and wrappers for the Windows API, but the official Windows message for this event is WM_RBUTTONDOWN. The latter is a standard window message sent to a window procedure when the user presses the right mouse button within the window’s client area. WMRBUTTONDOWN itself is not a formal constant defined in the Windows headers, yet some documentation or libraries may reference it informally as a shorthand for the same event.

When a window procedure receives the WM_RBUTTONDOWN message, it indicates that the right mouse button has been pressed. The wParam parameter contains the state of modifier keys and mouse buttons at the moment of the event, while lParam encodes the cursor position in the window’s client coordinates. Applications commonly extract the x and y coordinates using helper macros and then perform actions such as initiating a custom operation or preparing to display a context menu at that location.

Typical handling in code involves a window procedure dispatching on WM_RBUTTONDOWN to implement right-click behavior. If a default context menu is desired, many applications either process WM_CONTEXTMENU as well, or rely on the default window procedure via DefWindowProc. The exact behavior can vary between apps and frameworks, but the underlying event represents the user’s intention to press the right mouse button within the window.

Related messages include WM_RBUTTONUP, WM_LBUTTONDOWN, WM_MBUTTONDOWN, and WM_CONTEXTMENU, all of which participate in standard mouse interaction patterns in Win32 programming. Understanding WM_RBUTTONDOWN (and any informal alias like WMRBUTTONDOWN) is fundamental for implementing responsive, mouse-driven interfaces in Windows applications.