Custom Resize Handle in Border-less Form C#

Question

I\'m attempting to make border-less forms that pop out of a tool bar. I want the user to be able to grab at the bottom-right corner (a \"resize handle\") and be able to resi

Answer 1

just little modification to your code. I've added WM_MOUSEMOVE message handling:

    protected override void WndProc(ref Message m)
    {
        const UInt32 WM_NCHITTEST = 0x0084;
        const UInt32 WM_MOUSEMOVE = 0x0200;
        const UInt32 HTBOTTOMRIGHT = 17;
        const int RESIZE_HANDLE_SIZE = 10;
        bool handled = false;
        if (m.Msg == WM_NCHITTEST || m.Msg == WM_MOUSEMOVE )
        {
            Size formSize = this.Size;
            Point screenPoint = new Point(m.LParam.ToInt32());
            Point clientPoint = this.PointToClient(screenPoint);
            Rectangle hitBox = new Rectangle(formSize.Width - RESIZE_HANDLE_SIZE, formSize.Height - RESIZE_HANDLE_SIZE, RESIZE_HANDLE_SIZE, RESIZE_HANDLE_SIZE);
            if (hitBox.Contains(clientPoint))
            {
                m.Result = (IntPtr)HTBOTTOMRIGHT;
                handled = true;
            }
        }

        if (!handled)
            base.WndProc(ref m);
    }

by the way, you can draw system specific window size grip with ControlPaint.DrawSizeGrip Method http://msdn.microsoft.com/en-us/library/2e1yx2sa.aspx