实现无边框窗体的拖动及窗体大小变化

无边框窗体如何实现用鼠标拖动窗体边缘实现窗体大小变动呢？通过以下几个步骤即可实现：
1.实现WM_NCHITTEST消息，实现四条边框的模拟
2.实现WM_NCLBUTTONDOWN，发送窗体拖曳变化的消息
 

具体阐述如下：

1. 实现WM_NCHITTEST消息，实现四条边框的模拟，参考代码如下：

LRESULT CNoBorderWndChangeSizeDlg::OnNcHitTest(CPoint point)  {  // TODO: 在此添加消息处理程序代码和/或调用默认值     CRect rect;  GetWindowRect(&rect);  CRect rect1 = rect;  rect1.DeflateRect(10, 10, -10, -10);  rect1.NormalizeRect();  if (point.x <= rect.left+3)      return HTLEFT;  else if (point.x >= rect.right-3)      return HTRIGHT;  else if (point.y <= rect.top+3)      return HTTOP;  else if (point.y >= rect.bottom-3)      return HTBOTTOM;  else if (point.x <= rect.left+10 && point.y <= rect.top+10)      return HTTOPLEFT;  else if (point.x >= rect.right-10 && point.y <= rect.top+10)      return HTTOPRIGHT;  else if (point.x <= rect.left+10 && point.y >= rect.bottom-10)      return HTBOTTOMLEFT;  else if (point.x >= rect.right-10 && point.y >= rect.bottom-10)      return HTBOTTOMRIGHT;  else if (!rect.IsRectEmpty())  {      LRESULT uRet = CWnd::OnNcHitTest(point);      uRet = (uRet == HTCLIENT) ? HTCAPTION : uRet;      return uRet;  }  else  {      return CWnd::OnNcHitTest(point);  }  return 0;  } 

2. 实现WM_NCLBUTTONDOWN，发送窗体拖曳变化的消息

void CNoBorderWndChangeSizeDlg::OnNcLButtonDown(UINT nHitTest, CPoint point)  {      // TODO: 在此添加消息处理程序代码和/或调用默认值          if (nHitTest == HTTOP)      {                 SendMessage( WM_SYSCOMMAND, SC_SIZE | WMSZ_TOP, MAKELPARAM(point.x, point.y));      }      else if (nHitTest == HTBOTTOM)          SendMessage( WM_SYSCOMMAND, SC_SIZE | WMSZ_BOTTOM, MAKELPARAM(point.x, point.y));      else if (nHitTest == HTLEFT)          SendMessage( WM_SYSCOMMAND, SC_SIZE | WMSZ_LEFT, MAKELPARAM(point.x, point.y));      else if (nHitTest == HTRIGHT)          SendMessage( WM_SYSCOMMAND, SC_SIZE | WMSZ_RIGHT, MAKELPARAM(point.x, point.y));      else if (nHitTest == HTTOPLEFT)          SendMessage( WM_SYSCOMMAND, SC_SIZE | WMSZ_TOPLEFT, MAKELPARAM(point.x, point.y));      else if (nHitTest == HTTOPRIGHT)          SendMessage( WM_SYSCOMMAND, SC_SIZE | WMSZ_TOPRIGHT, MAKELPARAM(point.x, point.y));      else if (nHitTest == HTBOTTOMLEFT)          SendMessage( WM_SYSCOMMAND, SC_SIZE | WMSZ_BOTTOMLEFT, MAKELPARAM(point.x, point.y));      else if (nHitTest == HTBOTTOMRIGHT)          SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_BOTTOMRIGHT, MAKELPARAM(point.x, point.y));      else if (nHitTest==HTCAPTION)          SendMessage(WM_SYSCOMMAND, SC_MOVE | 4, MAKELPARAM(point.x, point.y));  } 

通常，使用上述的代码即可实现要求。
我们进行一下扩展。在窗体大小发生变化时，有两种表现形式：一种是出现虚线框，一种没有。这个选择依赖于操作系统，你可以右击桌面/属性/外观/效果中通过选择或取消“拖动时显示窗口内容”来表现这两种形式。那么如何在程序中实现而不依赖于当前机器的设置呢（这里的意思是不依赖手动选择“拖动时显示窗口内容”项），我们可以在OnNcLButtonDown函数中通过加入如下的代码实现:

if(nHitTest == HTTOP)  {             SystemParametersInfo(SPI_SETDRAGFULLWINDOWS, TRUE, NULL, 0);      SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_TOP, MAKELPARAM(point.x, point.y));      SystemParametersInfo(SPI_SETDRAGFULLWINDOWS, FALSE, NULL, 0);  }  

这段代码意思是在拖动上边缘动作之前，设置“拖动时显示窗口内容”，当该动作结束后，恢复原来的设置。当然，更好的做法是你首先获取机器当前的选项是什么，函数依旧是SystemParametersInfo，只是选项变化，具体查看MSDN即可。