窗體分為兩部分：客戶區(Client area)和非客戶區(Non-Client area)
WM_PAINT消息、OnPaint()方法、GetDC()API函數都是處理窗體客戶區繪制的
而標題欄處於非客戶區中，所以WM_PAINT消息、OnPaint()方法、GetDC()API函數都用不上
GetWindowDC()是獲得整個窗體的畫布句柄(Device Context翻譯為：設備清單，我習慣稱為畫布句柄)，包括非客戶區
GDI的繪制都離不開DC，因為操作系統必須知道你要在什么地方繪制圖形
當其他窗體遮擋或者移開，系統都會重新繪制窗體。這時就會發出WM_PAINT和WM_NCPAINT消息通知窗體重繪界面。
收到WM_NCPAINT消息(非客戶區繪制消息)說明非客戶區正需要重新繪制
重載WndProc()方法(窗體消息處理過程)，處理WM_NCPAINT等消息即可....
“基本的步驟” 就是：截獲WM_NCPAINT消息、得到窗體完整畫布句柄、在完整畫布上繪制圖形。
WM_NCPAINT WM_NCCALCSIZE WM_NCACTIVATE WM_NCHITTEST
建議樓主搜索關鍵詞：“C# WM_NCPAINT WndProc Graphics”得到更多的參考資料
貼
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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();
//標題欄按鈕的矩形區域。
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轉換為.NET的Graphics就可以很方便地使用Framework提供的繪圖功能了
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();
//釋放GDI資源
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;
}
}
}
//在窗口大小改變時及時更新按鈕的區域。
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;
}
}
}