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 WM_MBUTTONDBLCLK

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.

A window receives this message through its WindowProc function.

    LRESULT CALLBACK WindowProc(
      HWND hwnd,       // handle to window
      UINT uMsg,       // WM_MBUTTONDBLCKL
      WPARAM wParam,   // key indicator
      LPARAM lParam    // horizontal and vertical position
    );

Parameters

• wParam Indicates whether various virtual keys are down. This parameter can be one or more of the following values. Value Description MK_CONTROL The CTRL key is down. MK_LBUTTON The left mouse button is down. MK_MBUTTON The middle mouse button is down. MK_RBUTTON The right mouse button is down. MK_SHIFT The SHIFT key is down. MK_XBUTTON1 Windows 2000 or later: The first X button is down. MK_XBUTTON2 Windows 2000 or later: The second X button is down.
• lParam The low-order word specifies the x-coordinate of the cursor. The coordinate is relative to the upper-left corner of the client area. The high-order word 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

Use the following code to obtain the horizontal and vertical position:

xPos = GET_X_LPARAM(lParam); yPos = GET_Y_LPARAM(lParam); You can also use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.

Only windows that have the CS_DBLCLKS style can receive WM_MBUTTONDBLCLK messages, which the system generates when 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.

Requirements

  Windows NT/2000 or later: Requires Windows NT 3.1 or later.
  Windows 95/98/Me: Requires Windows 95 or later.
  Header: Declared in Winuser.h; include Windows.h.

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Notebook exported on Monday, 7 July 2008, 18:56:50 PM Eastern Daylight Time