Function EnumChildFindPoint

source/script2.cpp:5510–5560

BOOL CALLBACK EnumChildFindPoint(HWND aWnd, LPARAM lParam)
// This is called by more than one caller.  It finds the most appropriate child window that contains
// the specified point (the point should be in screen coordinates).
{
	point_and_hwnd_type &pah = *(point_and_hwnd_type *)lParam;  // For performance and convenience.
	if (!IsWindowVisible(aWnd) // Omit hidden controls, like Window Spy does.
		|| (pah.ignore_disabled_controls && !IsWindowEnabled(aWnd))) // For ControlClick, also omit disabled controls, since testing shows that the OS doesn't post mouse messages to them.
		return TRUE;
	RECT rect;
	if (!GetWindowRect(aWnd, &rect))
		return TRUE;
	// The given point must be inside aWnd's bounds.  Then, if there is no hwnd found yet or if aWnd
	// is entirely contained within the previously found hwnd, update to a "better" found window like
	// Window Spy.  This overcomes the limitations of WindowFromPoint() and ChildWindowFromPoint().
	// The pixel at (left, top) lies inside the control, whereas MSDN says "the pixel at (right, bottom)
	// lies immediately outside the rectangle" -- so use < instead of <= below:
	if (pah.pt.x >= rect.left && pah.pt.x < rect.right && pah.pt.y >= rect.top && pah.pt.y < rect.bottom)
	{
		// If the window's center is closer to the given point, break the tie and have it take
		// precedence.  This solves the problem where a particular control from a set of overlapping
		// controls is chosen arbitrarily (based on Z-order) rather than based on something the
		// user would find more intuitive (the control whose center is closest to the mouse):
		double center_x = rect.left + (double)(rect.right - rect.left) / 2;
		double center_y = rect.top + (double)(rect.bottom - rect.top) / 2;
		// Taking the absolute value first is not necessary because it seems that qmathHypot()
		// takes the square root of the sum of the squares, which handles negatives correctly:
		double distance = qmathHypot(pah.pt.x - center_x, pah.pt.y - center_y);
		//double distance = qmathSqrt(qmathPow(pah.pt.x - center_x, 2) + qmathPow(pah.pt.y - center_y, 2));
		bool update_it = !pah.hwnd_found;
		if (!update_it)
		{
			// If the new window's rect is entirely contained within the old found-window's rect, update
			// even if the distance is greater.  Conversely, if the new window's rect entirely encloses
			// the old window's rect, do not update even if the distance is less:
			if (rect.left >= pah.rect_found.left && rect.right <= pah.rect_found.right
				&& rect.top >= pah.rect_found.top && rect.bottom <= pah.rect_found.bottom)
				update_it = true; // New is entirely enclosed by old: update to the New.
			else if (   distance < pah.distance &&
				(pah.rect_found.left < rect.left || pah.rect_found.right > rect.right
					|| pah.rect_found.top < rect.top || pah.rect_found.bottom > rect.bottom)   )
				update_it = true; // New doesn't entirely enclose old and new's center is closer to the point.
		}
		if (update_it)
		{
			pah.hwnd_found = aWnd;
			pah.rect_found = rect; // And at least one caller uses this returned rect.
			pah.distance = distance;
		}
	}
	return TRUE; // Continue enumeration all the way through.
}