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WM_NCLBUTTONDOWN message

Posted when the user presses the left mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.

A window receives this message through its WindowProc function.


#define WM_NCLBUTTONDOWN                0x00A1

Parameters

wParam

The hit-test value returned by the DefWindowProc function as a result of processing the WM_NCHITTEST message. For a list of hit-test values, see WM_NCHITTEST.

lParam

A POINTS structure that contains the x- and y-coordinates of the cursor. The coordinates are relative to the upper-left corner of the screen.

Return value

If an application processes this message, it should return zero.

Remarks

The DefWindowProc function tests the specified point to find the location of the cursor and performs the appropriate action. If appropriate, DefWindowProc sends the WM_SYSCOMMAND message to the window.

You can also use the GET_X_LPARAM and GET_Y_LPARAM macros to extract the values of the x- and y- coordinates from lParam.


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

Important  Do not use the LOWORD or HIWORD macros to extract the x- and y- coordinates of the cursor position because these macros return incorrect results on systems with multiple monitors. Systems with multiple monitors can have negative x- and y- coordinates, and LOWORD and HIWORD treat the coordinates as unsigned quantities.

Requirements

Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]

Header

Winuser.h (include Windowsx.h)

See also

Reference
DefWindowProc
GET_X_LPARAM
GET_Y_LPARAM
WM_NCHITTEST
WM_NCLBUTTONDBLCLK
WM_NCLBUTTONUP
WM_SYSCOMMAND
Conceptual
Mouse Input
Other Resources
MAKEPOINTS
POINTS

 

 

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