System.Windows.Forms.CustomTabControl.CustomPaint C# (CSharp) Method

        private void CustomPaint(Graphics screenGraphics)
        {
            //	We render into a bitmap that is then drawn in one shot rather than using
            //	double buffering built into the control as the built in buffering
            // 	messes up the background painting.
            //	Equally the .Net 2.0 BufferedGraphics object causes the background painting
            //	to mess up, which is why we use this .Net 1.1 buffering technique.

            //	Buffer code from Gil. Schmidt http://www.codeproject.com/KB/graphics/DoubleBuffering.aspx

            if (this.Width > 0 && this.Height > 0){
                if (this._BackImage == null){
                    //	Cached Background Image
                    this._BackImage = new Bitmap(this.Width, this.Height);
                    Graphics backGraphics = Graphics.FromImage(this._BackImage);
                    backGraphics.Clear(Color.Transparent);
                    this.PaintTransparentBackground(backGraphics, this.ClientRectangle);
                }

                this._BackBufferGraphics.Clear(Color.Transparent);
                this._BackBufferGraphics.DrawImageUnscaled(this._BackImage, 0, 0);

                this._TabBufferGraphics.Clear(Color.Transparent);

                if (this.TabCount > 0) {

                    //	When top or bottom and scrollable we need to clip the sides from painting the tabs.
                    //	Left and right are always multiline.
                    if (this.Alignment <= TabAlignment.Bottom && !this.Multiline){
                        this._TabBufferGraphics.Clip = new Region(new RectangleF(this.ClientRectangle.X + 3, this.ClientRectangle.Y, this.ClientRectangle.Width - 6, this.ClientRectangle.Height));
                    }

                    //	Draw each tabpage from right to left.  We do it this way to handle
                    //	the overlap correctly.
                    if (this.Multiline) {
                        for (int row = 0; row < this.RowCount; row++) {
                            for (int index = this.TabCount - 1; index >= 0; index--) {
                                if (index != this.SelectedIndex && (this.RowCount == 1 || this.GetTabRow(index) == row)) {
                                    this.DrawTabPage(index, this._TabBufferGraphics);
                                }
                            }
                        }
                    } else {
                        for (int index = this.TabCount - 1; index >= 0; index--) {
                            if (index != this.SelectedIndex) {
                                this.DrawTabPage(index, this._TabBufferGraphics);
                            }
                        }
                    }

                    //	The selected tab must be drawn last so it appears on top.
                    if (this.SelectedIndex > -1) {
                        this.DrawTabPage(this.SelectedIndex, this._TabBufferGraphics);
                    }
                }
                this._TabBufferGraphics.Flush();

                //	Paint the tabs on top of the background

                // Create a new color matrix and set the alpha value to 0.5
                ColorMatrix alphaMatrix = new ColorMatrix();
                alphaMatrix.Matrix00 = alphaMatrix.Matrix11 = alphaMatrix.Matrix22 = alphaMatrix.Matrix44 = 1;
                alphaMatrix.Matrix33 = this._StyleProvider.Opacity;

                // Create a new image attribute object and set the color matrix to
                // the one just created
                using (ImageAttributes alphaAttributes = new ImageAttributes()){

                    alphaAttributes.SetColorMatrix(alphaMatrix);

                    // Draw the original image with the image attributes specified
                    this._BackBufferGraphics.DrawImage(this._TabBuffer,
                                                       new Rectangle(0,0,this._TabBuffer.Width, this._TabBuffer.Height),
                                                       0,0,this._TabBuffer.Width, this._TabBuffer.Height, GraphicsUnit.Pixel,
                                                       alphaAttributes);
                }

                this._BackBufferGraphics.Flush();

                //	Now paint this to the screen

                //	We want to paint the whole tabstrip and border every time
                //	so that the hot areas update correctly, along with any overlaps

                //	paint the tabs etc.
                if (this.RightToLeftLayout){
                    screenGraphics.DrawImageUnscaled(this._BackBuffer, -1, 0);
                } else {
                    screenGraphics.DrawImageUnscaled(this._BackBuffer, 0, 0);
                }
            }
        }