WM_XBUTTONUP message

Posted when the user releases the first or second X 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.

#define WM_XBUTTONUP                    0x020C

Parameters

wParam

The low-order word indicates whether various virtual keys are down. It can be one or more of the following values.

Value	Meaning
MK_CONTROL 0x0008	The CTRL key is down.
MK_LBUTTON 0x0001	The left mouse button is down.
MK_MBUTTON 0x0010	The middle mouse button is down.
MK_RBUTTON 0x0002	The right mouse button is down.
MK_SHIFT 0x0004	The SHIFT key is down.
MK_XBUTTON1 0x0020	The first X button is down.
MK_XBUTTON2 0x0040	The second X button is down.

The high-order word indicates which button was released. It can be one of the following values:

Value	Meaning
XBUTTON1 0x0001	The first X button was released.
XBUTTON2 0x0002	The second X button was released.

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 value

If an application processes this message, it should return TRUE. For more information about processing the return value, see the Remarks section.

Remarks

Use the following code to get the information in the wParam parameter:

fwKeys = GET_KEYSTATE_WPARAM (wParam); 
fwButton = GET_XBUTTON_WPARAM (wParam); 

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

xPos = GET_X_LPARAM(lParam); 
yPos = GET_Y_LPARAM(lParam); 

As noted above, the x-coordinate is in the low-order short of the return value; the y-coordinate is in the high-order short (both represent signed values because they can take negative values on systems with multiple monitors). If the return value is assigned to a variable, you can use the MAKEPOINTS macro to obtain a POINTS structure from the return value. You can also use the GET_X_LPARAM or GET_Y_LPARAM macro to extract the x- or y-coordinate.

Unlike the WM_LBUTTONUP, WM_MBUTTONUP, and WM_RBUTTONUP messages, an application should return TRUE from this message if it processes it. Doing so will allow software that simulates this message on Windows systems earlier than Windows 2000 to determine whether the window procedure processed the message or called DefWindowProc to process it.

Requirements

See also

Reference

GET_KEYSTATE_WPARAM

GET_X_LPARAM

GET_XBUTTON_WPARAM

GET_Y_LPARAM

GetCapture

SetCapture

WM_XBUTTONDBLCLK

WM_XBUTTONDOWN

Conceptual

Mouse Input

Other Resources

MAKEPOINTS

POINTS