c# – 如何在.Net WinForms控件上绘制自定义边框

我一直在尝试为现有的.Net WinForms控件绘制自定义边框.我试过这个是通过创建一个类来控制我想要改变它的边框颜色,然后在绘画过程中尝试几个东西.我尝试过以下方法：

1.捕获WM_NCPAINT.这有点起作用.下面的代码的问题是,当控件调整大小时,边框将在右侧和底侧被切断.不好.

protected override void WndProc(ref Message m)
{
  if (m.Msg == NativeMethods.WM_NCPAINT) {
    WmNcPaint(ref m);
    return;
  }
  base.WndProc(ref m);
}

private void WmNcPaint(ref Message m)
{
  if (BorderStyle == BorderStyle.None) {
    return;
  }

  IntPtr hDC = NativeMethods.GetWindowDC(m.HWnd);
  if (hDC != IntPtr.Zero) {
    using (Graphics g = Graphics.FromHdc(hDC)) {
      ControlPaint.DrawBorder(g,new Rectangle(0,this.Width,this.Height),_BorderColor,ButtonBorderStyle.Solid);
    }
    m.Result = (IntPtr)1;
    NativeMethods.ReleaseDC(m.HWnd,hDC);
  }
}

2.覆盖void OnPaint.这适用于某些控件,但不是全部.这还要求您将BorderStyle设置为BorderStyle.None,并且您必须手动清除paint上的背景,否则调整大小时的you get this.

protected override void OnPaint(PaintEventArgs e)
{
  base.OnPaint(e);
  ControlPaint.DrawBorder(e.Graphics,ButtonBorderStyle.Solid);
}

3.重写void OnResize和void OnPaint(如方法2中所示).通过这种方式,它可以很好地调整大小,但是当Panel启用了AutoScroll时则不会,在这种情况下,当向下滚动时它将是look like this.如果我尝试使用WM_NCPAINT绘制边框,则Refresh()无效.

protected override void OnResize(EventArgs eventargs)
{
  base.OnResize(eventargs);
  Refresh();
}

建议非常欢迎.我想知道最好的方法是什么,对于多种类型的控件(我必须为多个默认的WinForms控件执行此操作).

解决方法

编辑：所以我想出了导致我最初问题的原因.经过很长一段时间的修补,试验和查看.Net框架源代码,这里有一个明确的方法(考虑到你有一个控件继承自你想要绘制自定义边框的控件)：

[DllImport("user32.dll")]
public static extern bool RedrawWindow(IntPtr hWnd,IntPtr lprcUpdate,IntPtr hrgnUpdate,RedrawWindowFlags flags);

[Flags()]
public enum RedrawWindowFlags : uint
{
  Invalidate = 0X1,InternalPaint = 0X2,Erase = 0X4,Validate = 0X8,NoInternalPaint = 0X10,NoErase = 0X20,NoChildren = 0X40,AllChildren = 0X80,UpdateNow = 0X100,EraseNow = 0X200,Frame = 0X400,NoFrame = 0X800
}

// Make sure that WS_BORDER is a style,otherwise borders aren't painted at all
protected override CreateParams CreateParams
{
  get
  {
    if (DesignMode) {
      return base.CreateParams;
    }
    CreateParams cp = base.CreateParams;
    cp.ExStyle &= (~0x00000200); // WS_EX_CLIENTEDGE
    cp.Style |= 0x00800000; // WS_BORDER
    return cp;
  }
}

// During OnResize,call RedrawWindow with Frame|UpdateNow|Invalidate so that the frame is always redrawn accordingly
protected override void OnResize(EventArgs e)
{
  base.OnResize(e);
  if (DesignMode) {
    RecreateHandle();
  }
  RedrawWindow(this.Handle,IntPtr.Zero,RedrawWindowFlags.Frame | RedrawWindowFlags.UpdateNow | RedrawWindowFlags.Invalidate);
}

// Catch WM_NCPAINT for painting
protected override void WndProc(ref Message m)
{
  if (m.Msg == NativeMethods.WM_NCPAINT) {
    WmNcPaint(ref m);
    return;
  }
  base.WndProc(ref m);
}

// Paint the custom frame here
private void WmNcPaint(ref Message m)
{
  if (BorderStyle == BorderStyle.None) {
    return;
  }

  IntPtr hDC = NativeMethods.GetWindowDC(m.HWnd);
  using (Graphics g = Graphics.FromHdc(hDC)) {
    g.DrawRectangle(new Pen(_BorderColor),this.Width - 1,this.Height - 1));
  }
  NativeMethods.ReleaseDC(m.HWnd,hDC);
}

简而言之,保持OnPaint不变,确保设置了WS_BORDER,然后捕获WM_NCPAINT并通过hDC绘制边框,并确保在OnResize中调用RedrawWindow.

这甚至可以扩展以绘制自定义滚动条,因为这是在WM_NCPAINT期间可以绘制的窗口框架的一部分.

我从中删除了我的旧答案.

编辑2：对于ComboBox,你必须在WndProc()中捕获WM_PAINT,因为由于某种原因,用于绘制ComboBox的.Net源不使用OnPaint(),而是使用WM_PAINT.所以像这样：

protected override void WndProc(ref Message m)
{
  base.WndProc(ref m);

  if (m.Msg == NativeMethods.WM_PAINT) {
    OnWmPaint();
  }
}

private void OnWmPaint()
{
  using (Graphics g = CreateGraphics()) {
    if (!_HasBorders) {
      g.DrawRectangle(new Pen(BackColor),this.Height - 1));
      return;
    }
    if (!Enabled) {
      g.DrawRectangle(new Pen(_BorderColorDisabled),this.Height - 1));
      return;
    }
    if (ContainsFocus) {
      g.DrawRectangle(new Pen(_BorderColorActive),this.Height - 1));
      return;
    }
    g.DrawRectangle(new Pen(_BorderColor),this.Height - 1));
  }
}

c# – 如何在.Net WinForms控件上绘制自定义边框

解决方法

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