用获取路径的方法得到圆形窗体

1.

[System.Runtime.InteropServices.DllImport("gdi32")]
   private static extern IntPtr BeginPath(IntPtr hdc);
  
   [System.Runtime.InteropServices.DllImport("gdi32")]
   private static extern int SetBkMode(IntPtr hdc,int nBkMode);
   const int TRANSPARENT = 1;
  
   [System.Runtime.InteropServices.DllImport("gdi32")]
   private static extern IntPtr EndPath(IntPtr hdc);  [System.Runtime.InteropServices.DllImport("gdi32")]
   private static extern IntPtr PathToRegion(IntPtr hdc);
  
   [System.Runtime.InteropServices.DllImport("gdi32")]
   private static extern int Ellipse(IntPtr hdc, int X1,int Y1, int X2,int Y2);
  
   [System.Runtime.InteropServices.DllImport("user32")]
   private static extern IntPtr SetWindowRgn(IntPtr hwnd,IntPtr hRgn,bool bRedraw);
  
   [System.Runtime.InteropServices.DllImport("user32")]
   private static extern IntPtr GetDC(IntPtr hwnd);

 
2.创建窗体

private void Form1_Load(object sender, System.EventArgs e)
   {
        IntPtr dc;
        IntPtr region;
        dc=GetDC(this.Handle); 
        BeginPath(dc);
        //根据路径创建不规则窗体
        SetBkMode(dc,TRANSPARENT);       //设置为透明模式
        Ellipse(dc,20,20,220,220);
        EndPath(dc);
        region=PathToRegion(dc);
        SetWindowRgn(this.Handle,region,true);  
   }

 
3.移动窗体过程

const int WM_NCHITTEST = 0x0084;
  const int HTCLIENT = 0x0001;
  const int HTCAPTION = 0x0002;
  protected override void WndProc(ref System.Windows.Forms.Message m)
   {
    switch(m.Msg)
    {
     case WM_NCHITTEST:
      base.WndProc(ref m);
      if (m.Result==(IntPtr)HTCLIENT)
       m.Result=(IntPtr)HTCAPTION;
      break;
     default:
      base.WndProc(ref m);
      break;
    }
  
   }