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 sent to the window that has captured the mouse.
WM_NCHITTEST
xPos = LOWORD(lParam); // horizontal position of cursor
yPos = HIWORD(lParam); // vertical position of cursor
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 resizable window (the user can click the mouse to resize the window vertically) |
HTBOTTOMLEFT | In the lower-left corner of a border of a resizable window (the user can click the mouse to resize the window diagonally) |
HTBOTTOMRIGHT | In the lower-right corner of a border of a resizable window (the user can click the mouse to resize the window diagonally) |
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 resizable window (the user can click the mouse to resize the window horizontally) |
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 resizable window (the user can click the mouse to resize the window horizontally) |
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 in the same thread (the message will be sent to underlying windows in the same thread until one of them returns a code that is not HTTRANSPARENT) |
HTVSCROLL | In the vertical scroll bar |
HTZOOM | In a Maximize button |
An application can use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in winuser.h.
Mouse Input Overview, Mouse Input Messages, DefWindowProc, MAKEPOINTS, POINTS