ComponentFactory.Krypton.Toolkit.RenderGlassHelpers.DrawBackGlassFade C# (CSharp) Method

        private static IDisposable DrawBackGlassFade(RectangleF drawRect,
                                                     RectangleF outerRect,
                                                     Color color1,
                                                     Color color2,
                                                     Color glassColor1,
                                                     Color glassColor2,
                                                     VisualOrientation orientation,
                                                     Graphics g,
                                                     IDisposable memento)
        {
            // Cannot draw a zero length rectangle
            if ((drawRect.Width > 0) && (drawRect.Height > 0) &&
                (outerRect.Width > 0) && (outerRect.Height > 0))
            {
                bool generate = true;
                MementoBackGlassFade cache;

                // Access a cache instance and decide if cache resources need generating
                if ((memento == null) || !(memento is MementoBackGlassFade))
                {
                    if (memento != null)
                        memento.Dispose();

                    cache = new MementoBackGlassFade(drawRect, outerRect, color1, color2,
                                                     glassColor1, glassColor2, orientation);
                    memento = cache;
                }
                else
                {
                    cache = (MementoBackGlassFade)memento;
                    generate = !cache.UseCachedValues(drawRect, outerRect, color1, color2,
                                                      glassColor1, glassColor2, orientation);
                }

                // Do we need to generate the contents of the cache?
                if (generate)
                {
                    // Dispose of existing values
                    cache.Dispose();

                    // Create gradient rect from the drawing rect
                    RectangleF gradientRect = new RectangleF(drawRect.X - 1, drawRect.Y - 1, drawRect.Width + 2, drawRect.Height + 2);

                    // Cannot draw a zero sized rectangle
                    if ((gradientRect.Width > 0) && (gradientRect.Height > 0))
                    {
                        // Draw a gradient from first to second over the length, but use the
                        // first color for the first 33% of distance and fade over the rest
                        cache.mainBrush = new LinearGradientBrush(gradientRect, color1, color2, AngleFromOrientation(orientation));
                        cache.mainBrush.Blend = _glassFadeBlend;
                    }

                    float glassLength;

                    // Glass covers 33% of the orienatated length
                    if (VerticalOrientation(orientation))
                        glassLength = (int)(outerRect.Height * 0.33f) + outerRect.Y - drawRect.Y;
                    else
                        glassLength = (int)(outerRect.Width * 0.33f) + outerRect.X - drawRect.X;

                    RectangleF glassRect;
                    RectangleF mainRect;

                    // Create rectangles that cover the glass and main area
                    switch (orientation)
                    {
                        case VisualOrientation.Left:
                            glassRect = new RectangleF(drawRect.X, drawRect.Y, glassLength, drawRect.Height);
                            break;
                        case VisualOrientation.Right:
                            mainRect = new RectangleF(drawRect.X, drawRect.Y, drawRect.Width - glassLength, drawRect.Height);
                            glassRect = new RectangleF(mainRect.Right, drawRect.Y, glassLength, drawRect.Height);
                            break;
                        case VisualOrientation.Top:
                        default:
                            glassRect = new RectangleF(drawRect.X, drawRect.Y, drawRect.Width, glassLength);
                            break;
                        case VisualOrientation.Bottom:
                            mainRect = new RectangleF(drawRect.X, drawRect.Y, drawRect.Width, drawRect.Height - glassLength);
                            glassRect = new RectangleF(drawRect.X, mainRect.Bottom, drawRect.Width, glassLength);
                            break;
                    }

                    // Create gradient rectangles
                    RectangleF glassGradientRect = new RectangleF(glassRect.X - 1, glassRect.Y - 1, glassRect.Width + 2, glassRect.Height + 2);

                    // Cannot draw a zero sized rectangle
                    if ((glassRect.Width > 0) && (glassRect.Height > 0) &&
                        (glassGradientRect.Width > 0) && (glassGradientRect.Height > 0))
                    {
                        // Use semi-transparent white colors to create the glass effect
                        cache.topBrush = new LinearGradientBrush(glassGradientRect, glassColor1, glassColor2, AngleFromOrientation(orientation));
                        cache.glassRect = glassRect;
                    }
                }

                if (cache.mainBrush != null)
                    g.FillRectangle(cache.mainBrush, drawRect);

                if (cache.topBrush != null)
                    g.FillRectangle(cache.topBrush, cache.glassRect);
            }

            return memento;
        }