C# 绘制窗体客户非客户区要用WM_PAINT和WM_NCPAINT

窗体分为两部分：客户区(Client area)和非客户区(Non-Client area) 
WM_PAINT消息、OnPaint()方法、GetDC()API函数都是处理窗体客户区绘制的 
  
而标题栏处于非客户区中，所以WM_PAINT消息、OnPaint()方法、GetDC()API函数都用不上 
  
GetWindowDC()是获得整个窗体的画布句柄(Device Context翻译为：设备清单，我习惯称为画布句柄)，包括非客户区 
  
GDI的绘制都离不开DC，因为操作系统必须知道你要在什么地方绘制图形 
  
当其他窗体遮挡或者移开，系统都会重新绘制窗体。这时就会发出WM_PAINT和WM_NCPAINT消息通知窗体重绘界面。 
  
收到WM_NCPAINT消息(非客户区绘制消息)说明非客户区正需要重新绘制 
  
重载WndProc()方法(窗体消息处理过程)，处理WM_NCPAINT等消息即可.... 
  
“基本的步骤” 就是：截获WM_NCPAINT消息、得到窗体完整画布句柄、在完整画布上绘制图形。 
    WM_NCPAINT WM_NCCALCSIZE WM_NCACTIVATE WM_NCHITTEST
建议楼主搜索关键词：“C# WM_NCPAINT WndProc Graphics”得到更多的参考资料 
贴

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[DllImport   ( "User32.dll ")] 

private   static   extern   IntPtr   GetWindowDC(IntPtr   hwnd); 

[DllImport   ( "User32.dll ")] 

private   static   extern   int   ReleaseDC(IntPtr   hwnd,   IntPtr   hdc); 

[DllImport   ( "Kernel32.dll ")] 

private   static   extern   int   GetLastError(); 

//标题栏按钮的矩形区域。 

Rectangle   m_rect   =   new   Rectangle(205,   6,   20,   20); 

protected   override   void   WndProc(ref   Message   m) 

{ 

base.WndProc(ref   m); 

switch(m.Msg) 

{ 

case   0x86://WM_NCACTIVATE 

goto   case   0x85; 

case   0x85://WM_NCPAINT 

{ 

IntPtr   hDC   =   GetWindowDC(m.HWnd); 

//把DC转换为.NET的Graphics就可以很方便地使用Framework提供的绘图功能了 

Graphics   gs   =   Graphics.FromHdc(hDC); 

gs.FillRectangle(new   LinearGradientBrush(m_rect,   Color.Pink,   Color.Purple,   LinearGradientMode.BackwardDiagonal),   m_rect); 

StringFormat   strFmt   =   new   StringFormat(); 

strFmt.Alignment   =   StringAlignment.Center; 

strFmt.LineAlignment   =   StringAlignment.Center; 

gs.DrawString( "√ ",   this.Font,   Brushes.BlanchedAlmond,   m_rect,   strFmt); 

gs.Dispose(); 

//释放GDI资源 

ReleaseDC(m.HWnd,   hDC); 

break; 

} 

case   0xA1://WM_NCLBUTTONDOWN 

{ 

Point   mousePoint   =   new   Point((int)m.LParam); 

mousePoint.Offset(-this.Left,   -this.Top); 

if(m_rect.Contains(mousePoint)) 

{ 

MessageBox.Show( "hello "); 

} 

break; 

} 

} 

} 

//在窗口大小改变时及时更新按钮的区域。 

private   void   Form1_SizeChanged(object   sender,   System.EventArgs   e) 

{ 

m_rect.X   =   this.Bounds.Width   -   95; 

m_rect.Y   =   6; 

m_rect.Width   =   m_rect.Height   =   20; 

} 

} 

}