I'm currently trying to override the OnPaint() method of a Custom Control I'm building.
The object is just a simple Panel, but I'm trying to make it look a different type of way, like this:

.

I'm using a GraphicsPath to help me try and complete this task, but it's not looking/behaving how I expected it to work as it currently looks like this:

.

Here is the code I've been working on to recreate Fig 1:

private GraphicsPath GetFigurePath(RectangleF rect)
{
    GraphicsPath path = new GraphicsPath();

    Point TopLeft = new Point((int)rect.X, (int)rect.Y);
    Point TopRight = new Point((int)rect.X   (int)rect.Width, (int)rect.Height);
    Point BottomLeft = new Point((int)rect.X, (int)rect.Y   (int)rect.Height);
    Point BottomRight = new Point((int)rect.X   (int)rect.Width, (int)rect.Y   (int)rect.Height);

    Point MidPoint = new Point((TopLeft.X   BottomLeft.X) / 2, (TopLeft.Y   BottomLeft.Y) / 2);
    Point Fulcrum = new Point((int)MidPoint.X   (int)rect.Width, MidPoint.Y);

    path.StartFigure();

    // The rectangle
    path.AddLine(TopLeft, TopRight);
    path.AddLine(TopRight, BottomRight);
    path.AddLine(BottomRight, BottomLeft);
    path.AddLine(BottomLeft, TopLeft);

    // The pointy end
    path.AddLine(TopRight, Fulcrum);
    path.AddLine(Fulcrum, BottomRight);

    path.CloseFigure();

    return path;
}

protected override void OnPaint(PaintEventArgs e)
{
    if (HasBorderStyle) {
        base.OnPaint(e);

        this.FlatStyle = FlatStyle.Flat;
        this.Size = new Size(DEFAULT_WIDTH, DEFAULT_HEIGHT);
        this.BackColor = Color.Silver;
        this.ForeColor = Color.White;
        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;


        RectangleF rectSurface = new RectangleF(0, 0, this.DEFAULT_WIDTH, this.DEFAULT_HEIGHT);
        RectangleF rectBorder = new RectangleF(1, 1, this.DEFAULT_WIDTH - 0.8f, this.DEFAULT_HEIGHT - 1);

        using (GraphicsPath pathSurface = GetFigurePath(rectSurface))
        using (GraphicsPath pathBorder = GetFigurePath(rectBorder))
        using (Pen penSurface = new Pen(this.Parent.BackColor, 2))
        using (Pen penBorder = new Pen(borderColour, borderSize)) {
            penBorder.Alignment = PenAlignment.Inset;
            this.Region = new Region(pathSurface);

            e.Graphics.DrawPath(penSurface, pathSurface);
            e.Graphics.DrawPath(penBorder, pathBorder);
        }
    }
}

Could anyone tell me what I'm missing or I'm doing wrong?

CodePudding user response：

A few pointers and an example on the use of

And at Run-Time:

See also:
How to avoid visual artifacts of colored border of zoomable UserControl with rounded corners?
How can I draw a rounded rectangle as the border for a rounded Form?
A shadow created with PathGradientBrush shows undesired thorn results

Custom Control:

using System.ComponentModel;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

[ToolboxItem(true)]
[DesignerCategory("code")]
public class NavigationShape : Control
{
    private Color m_ArrowColor = Color.SteelBlue;
    private Color m_BorderColor = Color.Orange;
    private float m_BorderSize = 1.5f;
    private bool m_BorderVisible = true;

    public NavigationShape() {
        SetStyle(ControlStyles.OptimizedDoubleBuffer | 
                 ControlStyles.AllPaintingInWmPaint | 
                 ControlStyles.ResizeRedraw, true);
        MinimumSize = new Size(40, 20);
    }

    protected override void OnResize(EventArgs e)
    {
        base.OnResize(e);
        Region = new Region(GetRegionPath());
    }

    private GraphicsPath GetRegionPath()
    {
        // The arrow shape begins at 3/4 or the current width of the container
        float arrowSection = ClientSize.Width * .75f;
        PointF[] arrowPoints = new PointF[] {
            new PointF (0, 0), 
            new PointF (arrowSection, 0),
            new PointF(ClientSize.Width, ClientSize.Height / 2.0f),
            new PointF (arrowSection, ClientSize.Height),
            new PointF (0, ClientSize.Height),
            new PointF (0, 0)
        };
        var path = new GraphicsPath();
        path.AddLines(arrowPoints);
        path.CloseFigure();
        return path;
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
        float border = m_BorderVisible ? m_BorderSize : .5f;

        using (var path = GetRegionPath()) {
            var rect = path.GetBounds();
            float scaleX = 1.0f - ((border * 2.5f) / rect.Width);
            float scaleY = 1.0f - ((border * 2.0f) / rect.Height);

            using (var mx = new Matrix(scaleX, 0, 0, scaleY, border, border))
            using (var brush = new SolidBrush(m_ArrowColor)) {
                path.Transform(mx);
                e.Graphics.FillPath(brush, path);
                if (m_BorderVisible) {
                    using (Pen pen = new Pen(m_BorderColor, m_BorderSize)) {
                        e.Graphics.DrawPath(pen, path);
                    }
                }
            }
        }
        base.OnPaint(e);
    }


    [DefaultValue(typeof(Color), "SteelBlue")]
    [Description("Color of the shape")]
    public Color ArrowColor {
        get => m_ArrowColor;
        set {
            if (m_ArrowColor != value) {
                m_ArrowColor = value;
                Invalidate();
            }
        }
    }

    [DefaultValue(true)]
    [Description("Show or hide the Border")]
    public bool BorderVisible {
        get => m_BorderVisible;
        set {
            m_BorderVisible = value;
            Invalidate();
        }
    }

    [DefaultValue(typeof(Color), "Orange")]
    [Description("Color of the Border")]
    public Color BorderColor {
        get => m_BorderColor;
        set {
            if (m_BorderColor != value) {
                m_BorderColor = value;
                Invalidate();
            }
        }
    }

    [DefaultValue(1.5f)]
    [Description("Size of the Border [1.0, 6.0]")]
    public float BorderSize {
        get => m_BorderSize;
        set {
            if (m_BorderSize != value) {
                m_BorderSize = Math.Max(Math.Min(value, 6.0f), 1.0f);
                Invalidate();
            }
        }
    }

    [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public BorderStyle BorderStyle{ get; set; }  // Implement if needed
}