c# - 如何绘制圆角矩形作为圆角窗体的边框？

Question

我正在创建一个具有圆形边框的表单(如 this question 所示)。
由于这个人似乎也有问题，我似乎无法绘制圆形边框。

这是我用来设置实际边框形状的代码:

// ... within InitializeComponent ...
this.FormBorderStyle = FormBorderStyle.None;
IntPtr handle = CreateRoundRectRgn(0, 0, Width, Height, 20, 20);
Region = System.Drawing.Region.FromHrgn(handle);
DeleteObject(handle);

this.ResizeRedraw = true;

这是覆盖 OnPaint 并绘制边框轮廓的代码。

protected override void OnPaint(PaintEventArgs e)
{
     // I've tried modifying the parameters here.
     GraphicsPath path = MyRoundedRectangle.Create(0, 0, Width, Height, 10, MyRoundedRectangle.RectangleCorners.All);

     Pen p = new Pen(Brushes.Black, 3f);
     e.Graphics.DrawPath(p, path);
}

MyRoundedRectangle 的内容与 this question 中提供的代码相同，其中答案链接到 this page ，其中包含 MyRoundedRectangle 的代码。

我想要一个完整的环绕边框，但我得到的是:

Answer 1

注释中描述内容的基本实现。
表单 frmRoundCorners 提供了一些属性，允许使用自定义 BackColor、自定义 BorderColor 和自定义内部边框颜色绘制其圆形区域，充当 阴影 用于窗体边框的内侧。

Form 本身是使用基类 baseForm 实现的，该基类派生自 Form，因此可以在 Form 中设置 Form 的属性设计师。

透明度被激活，将 Form 的原始 BackColor 设置为其 TrasparencyKey，使其 ClientArea 完全透明，但可绘制。
Form 的原始边框在基类构造函数中设置为 FormBorderStyle.None。
我没有设置特定的 BackColor/TransparencyKey 颜色(它必须在表单设计器中设置)，因为我认为这是需要试验的东西。我建议使用中灰色。避免红色成分。

可以移动表单，点击它的 ClientArea 的任意点并拖动它。

窗体及其自定义边框的最小/最大曲率设置为 15 和 180 度。它不能使用 PropertyGrid 更改为不同的范围。
表单的圆角区域及其边框是使用 GraphicsPath.AddArc() 绘制的方法，然后应用 Matrix在 Scale 和 Transform(位置)组件中转换为 Graphics 对象。 Size 组件保持不变。

这是它的样子:

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

[ToolboxItem(false)]
public partial class frmRoundCorners : baseForm
{
    private GraphicsPath pathRegion = new GraphicsPath(FillMode.Winding);
    private GraphicsPath pathBorder;
    Point pMousePosition = Point.Empty;

    public frmRoundCorners()
    {
        SetStyle(ControlStyles.AllPaintingInWmPaint |
                 ControlStyles.UserPaint |
                 ControlStyles.OptimizedDoubleBuffer |
                 ControlStyles.ResizeRedraw, true);
        InitializeComponent();
    }

    protected override void OnMouseDown(MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left) {
            pMousePosition = e.Location;
        }
        base.OnMouseDown(e);
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left) {
            Point screenPos = PointToScreen(e.Location);
            this.Location = new Point(screenPos.X - pMousePosition.X, screenPos.Y - pMousePosition.Y);
        }
        base.OnMouseMove(e);
    }

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

        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
        e.Graphics.PixelOffsetMode = PixelOffsetMode.Half;
        RoundedCornerRectangle(ClientRectangle);
        RectangleF rect = pathRegion.GetBounds();
        float scaleX = 1 - (BorderSize / rect.Width);
        float scaleY = 1 - (BorderSize / rect.Height);
        using (Pen pen = new Pen(BorderColor, BorderSize))
        using (Pen penBorder = new Pen(InternalBorderColor, 2))
        using (var brush = new SolidBrush(FillColor))
        using (var mx = new Matrix(scaleX, 0, 0, scaleY, (pen.Width / 2), (pen.Width / 2)))
        {
            e.Graphics.Transform = mx;
            e.Graphics.FillPath(brush, pathRegion);
            e.Graphics.DrawPath(penBorder, pathBorder);
            e.Graphics.DrawPath(pen, pathRegion);
        }
    }

    private void RoundedCornerRectangle(Rectangle r)
    {
        pathRegion = new GraphicsPath(FillMode.Alternate);
        float innerCurve = CurveAngle - m_PenSizeOffset;

        pathRegion.StartFigure();
        pathRegion.AddArc(r.X, r.Y, CurveAngle, CurveAngle, 180, 90);
        pathRegion.AddArc(r.Right - CurveAngle, r.Y, CurveAngle, CurveAngle, 270, 90);
        pathRegion.AddArc(r.Right - CurveAngle, r.Bottom - CurveAngle, CurveAngle, CurveAngle, 0, 90);
        pathRegion.AddArc(r.X, r.Bottom - CurveAngle, CurveAngle, CurveAngle, 90, 90);
        pathRegion.CloseFigure();

        pathBorder = new GraphicsPath();
        pathBorder.StartFigure();
        pathBorder.AddArc(r.X + m_PenSizeOffset, r.Y + m_PenSizeOffset, innerCurve, innerCurve, 180, 90);
        pathBorder.AddArc(r.Right - innerCurve - m_PenSizeOffset, r.Y + m_PenSizeOffset, innerCurve, innerCurve, 270, 90);
        pathBorder.AddArc(r.Right - innerCurve - m_PenSizeOffset, r.Bottom - innerCurve- m_PenSizeOffset, innerCurve, innerCurve, 0, 90);
        pathBorder.AddArc(r.X + m_PenSizeOffset, r.Bottom - innerCurve - m_PenSizeOffset, innerCurve, innerCurve, 90, 90);
        pathBorder.CloseFigure();
    }
}

baseForm 类:

public class baseForm : Form
{
    private Color m_InternalBorderColor = Color.FromArgb(128, 128, 128);
    private Color m_BorderColor = Color.Red;
    private Color m_FillColor = Color.WhiteSmoke;
    private float m_PenSize = 6f;
    private float m_CurveAngle = 60.0f;
    internal float m_PenSizeOffset = 3f;

    public baseForm() => InitializeComponent();
    private void InitializeComponent() => FormBorderStyle = FormBorderStyle.None;

    [EditorBrowsable(EditorBrowsableState.Always), Browsable(true), Category("Appearance")]
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
    [DefaultValue(60.0f)]
    public virtual float CurveAngle
    {
        get => m_CurveAngle;
        set {
            m_CurveAngle = Math.Max(Math.Min(value, 180), 15);
            Invalidate();
        }
    }
    [EditorBrowsable(EditorBrowsableState.Always), Browsable(true), Category("Appearance")]
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
    [DefaultValue(6.0f)]
    public virtual float BorderSize
    {
        get => m_PenSize;
        set {
            m_PenSize = value;
            m_PenSizeOffset = value / 2.0f;
            Invalidate();
        }
    }

    [EditorBrowsable(EditorBrowsableState.Always), Browsable(true), Category("Appearance")]
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
    public virtual Color BorderColor
    {
        get => m_BorderColor;
        set {
            m_BorderColor = value;
            Invalidate();
        }
    }

    [EditorBrowsable(EditorBrowsableState.Always), Browsable(true), Category("Appearance")]
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
    public virtual Color FillColor
    {
        get => m_FillColor;
        set {
            m_FillColor = value;
            Invalidate();
        }
    }

    [EditorBrowsable(EditorBrowsableState.Always), Browsable(true), Category("Appearance")]
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
    [Description("Get or Set the Color of the internal border")]
    public virtual Color InternalBorderColor
    {
        get => m_InternalBorderColor;
        set {
            m_InternalBorderColor = value;
            Invalidate();
        }
    }

    [EditorBrowsable(EditorBrowsableState.Never), Browsable(false)]
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    [DefaultValue(FormBorderStyle.None)]
    public new FormBorderStyle FormBorderStyle
    {
        get => base.FormBorderStyle;
        set => base.FormBorderStyle = FormBorderStyle.None;
    }
}