如何在.Net WinForms控件上绘制自定义边框

Question

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.抓住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, 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.这也需要你设置BorderStyle为BorderStyle.None,你必须手动清除油漆背景,否则你在调整大小时得到这个.

protected override void OnPaint(PaintEventArgs e)
{
  base.OnPaint(e);
  ControlPaint.DrawBorder(e.Graphics, new Rectangle(0, 0, this.Width, this.Height), _BorderColor, ButtonBorderStyle.Solid);
}

3.覆盖void OnResize和void OnPaint(如方法2).通过这种方式,它可以很好地调整大小,但是当Panel AutoScroll启用时则不会,在这种情况下,向下滚动时它将看起来像这样.如果我尝试使用WM_NCPAINT边框绘制,Refresh()则无效.

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).

Answer 1

编辑：所以我弄清楚是什么导致了我最初的问题。经过很长时间的修补、试验和研究 .Net 框架源代码，这里有一个明确的方法来实现它（考虑到您有一个继承自要在其上绘制自定义边框的控件的控件）：

[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, 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), new Rectangle(0, 0, this.Width - 1, this.Height - 1));
  }
  NativeMethods.ReleaseDC(m.HWnd, hDC);
}

简而言之，保持 OnPaint 不变，确保WS_BORDER已设置，然后WM_NCPAINT通过 hDC 捕获并绘制边框，并确保RedrawWindow在OnResize.

这甚至可以扩展以绘制自定义滚动条，因为这是窗口框架的一部分，您可以在WM_NCPAINT.

我从中删除了我的旧答案。

编辑2：对于ComboBox，您必须捕获WM_PAINT，WndProc()因为由于某种原因，用于绘制 的 .Net 源ComboBox不使用OnPaint()，但是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), new Rectangle(0, 0, this.Width - 1, this.Height - 1));
      return;
    }
    if (!Enabled) {
      g.DrawRectangle(new Pen(_BorderColorDisabled), new Rectangle(0, 0, this.Width - 1, this.Height - 1));
      return;
    }
    if (ContainsFocus) {
      g.DrawRectangle(new Pen(_BorderColorActive), new Rectangle(0, 0, this.Width - 1, this.Height - 1));
      return;
    }
    g.DrawRectangle(new Pen(_BorderColor), new Rectangle(0, 0, this.Width - 1, this.Height - 1));
  }
}