WinForm Controls + Transparency

Answer 1

Short version:

I found a way around the problem.

It has to do with using the control's REGION.

By altering the Region of the control, I managed to fake a functional transparency system. It may not be the most efficient or user-friendly method, but it gets the job done.

        int SizeW = this.Size.Width;
        int SizeH = this.Size.Height;
        int ArcSize = (int)((float)SizeW * 0.40 );

        if (tabType == TabType.LeftTab)
        {
            //Make a six-sided polygon, a rectangle with the "outside" corners cut off.
            //The next step will round the corners with Arcs
            Point[] points = new Point[] { 
                new Point(SizeW, 0), new Point(ArcSize, 0),
                new Point(0,ArcSize), new Point(0,SizeH-ArcSize), 
                new Point(ArcSize,SizeH), new Point(SizeW,SizeH)};
            Byte[] bytes = new byte[] { 
                1, 1, 
                1, 1, 
                1, 1};
            System.Drawing.Drawing2D.FillMode fm =
                System.Drawing.Drawing2D.FillMode.Winding;

            System.Drawing.Drawing2D.GraphicsPath tempGP =
                new System.Drawing.Drawing2D.GraphicsPath(points, bytes, fm);

            //add the arcs
            ArcSize = ArcSize * 2;
            tempGP.AddArc(0, 0, ArcSize, ArcSize, -90, -90);
            tempGP.CloseFigure();
            tempGP.AddArc(0, SizeH - ArcSize, ArcSize, ArcSize, 180, -90);
            tempGP.CloseFigure();

            Region tempRegion = new Region(tempGP);
            this.Region = new Region(tempGP);
        }