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WM_NCHITTEST Overview  Group

The WM_NCHITTEST message is sent to a window when the cursor moves, or when a mouse button is pressed or released. If the mouse is not captured, the message is sent to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse. 

WM_NCHITTEST 

xPos = LOWORD(lParam);  // horizontal position of cursor 

yPos = HIWORD(lParam);  // vertical position of cursor 

 

Parameters

xPos
Value of the low-order word of lParam. Specifies the x-coordinate of the cursor. The coordinate is relative to the upper-left corner of the screen.
yPos
Value of the high-order word of lParam. Specifies the y-coordinate of the cursor. The coordinate is relative to the upper-left corner of the screen.

Return Values

The return value of the DefWindowProc function is one of the following values, indicating the position of the cursor hot spot:

Value

Location of hot spot

HTBORDER

In the border of a window that does not have a sizing border

HTBOTTOM

In the lower horizontal border of a window

HTBOTTOMLEFT

In the lower-left corner of a window border

HTBOTTOMRIGHT

In the lower-right corner of a window border

HTCAPTION

In a title bar

HTCLIENT

In a client area

HTCLOSE

In a close button

HTERROR

On the screen background or on a dividing line between windows (same as HTNOWHERE, except that the DefWindowProc function produces a system beep to indicate an error)

HTGROWBOX

In a size box (same as HTSIZE)

HTHELP

In a Help button

HTHSCROLL

In a horizontal scroll bar

HTLEFT

In the left border of a window

HTMENU

In a menu

HTMAXBUTTON

In Maximize button

HTMINBUTTON

In Minimize button

HTNOWHERE

On the screen background or on a dividing line between windows

HTREDUCE

In a Minimize button

HTRIGHT

In the right border of a window

HTSIZE

In a size box (same as HTGROWBOX)

HTSYSMENU

In a System menu or in a Close button in a child window

HTTOP

In the upper horizontal border of a window

HTTOPLEFT

In the upper-left corner of a window border

HTTOPRIGHT

In the upper right corner of a window border

HTTRANSPARENT

In a window currently covered by another window

HTVSCROLL

In the vertical scroll bar

HTZOOM

In a Maximize button

Remarks

An application can use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.

See Also

DefWindowProc, MAKEPOINTS, POINTS