WM_NCHITTEST

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
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)
HTHSCROLL	In a horizontal scroll bar
HTLEFT	In the left border of a window
HTMENU	In a menu
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

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