WM_NCHITTEST
xPos = (int) LOWORD(lParam); /* horizontal position of cursor */
yPos = (int) HIWORD(lParam); /* vertical position of cursor */The WM_NCHITTEST message is sent to the window that contains the cursor or to the window that used the SetCapture function to capture the mouse input. It is sent every time the mouse is moved.
xPos
Value of the low-order word of lParam. Specifies the x-coordinate of the cursor, in screen coordinates.
yPos
Value of the high-order word of lParam. Specifies the y-coordinate of the cursor, in screen coordinates.
The return value of the DefWindowProc function is one of the following values indicating the position of the cursor:
| Value | Meaning |
| 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 area |
| 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 the horizontal scroll bar |
| HTLEFT | In the left border of a window |
| HTMAXBUTTON | In a Maximize button |
| HTMENU | In a menu area |
| HTMINBUTTON | In a 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 (sometimes referred to as a Control 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 |
The MAKEPOINT macro can be used to convert the lParam parameter to a POINT structure.
This example shows a portion of a subclass procedure that detects mouse messages in a static window:
LONG lRetVal;
case WM_NCHITTEST:
lRetVal = DefWindowProc(hwnd, msg, wParam, lParam);
if (lRetVal == HTTRANSPARENT) {
.
. /* Process mouse events in static window. */
.
}
break;
default:
CallWindowProc(lpStaticProc, hwnd, msg, wParam, lParam);