protected override void WndProc(ref Message m) { base.WndProc(ref m); if (!HandleMouseOnGlass || !_glassEnabled) { return; } // Respond to hit test messages with Caption if mouse on glass: // this automatically enables form dragging on glass if (m.Msg == (int)WindowMessage.WM_NCHITTEST && m.Result.ToInt32() == (int)HitTest.HTCLIENT) { // Check if mouse pointer is on glass part of form if (_glassFull) { m.Result = (IntPtr)HitTest.HTCAPTION; } else { uint lparam = (uint)m.LParam.ToInt32(); ushort x = IntHelpers.LowWord(lparam); ushort y = IntHelpers.HighWord(lparam); var clientPoint = PointToClient(new System.Drawing.Point(x, y)); if (_glassMargins.IsOutside(clientPoint, ClientSize)) { m.Result = (IntPtr)HitTest.HTCAPTION; } } } }