[MFC] 无边框窗口的Resize拖动效果的实现（上）

众所周知：当窗口是Resizing类型时 会自带resize效果（鼠标悬停在窗口边缘时 会有resize光标 点击拖动可以修改窗口的宽高）

但是 实际的窗口程序因为考虑到界面美化 通常需要去掉自带的border 这样窗口就没有自带的resize功能了

针对这类窗口 如何实现resize效果？实现这几个消息的响应函数即可：

WM_NCHITTEST

WM_SETCURSOR

WM_NCLBUTTONDOWN

代码如下：

#define RESIZE_REGION_SIZE  5

LRESULT CMyDlg::OnNcHitTest(CPoint pt)
{
RECT rcWindow;
::GetWindowRect(m_hWnd, &rcWindow);

// 最好将四个角的判断放在前面
if (pt.x <= rcWindow.left + RESIZE_REGION_SIZE && pt.y <= rcWindow.top + RESIZE_REGION_SIZE)
return HTTOPLEFT;
else if (pt.x >= rcWindow.right - RESIZE_REGION_SIZE && pt.y <= rcWindow.top + RESIZE_REGION_SIZE)
return HTTOPRIGHT;
else if (pt.x <= rcWindow.left + RESIZE_REGION_SIZE && pt.y >= rcWindow.bottom - RESIZE_REGION_SIZE)
return HTBOTTOMLEFT;
else if (pt.x >= rcWindow.right - RESIZE_REGION_SIZE && pt.y >= rcWindow.bottom - RESIZE_REGION_SIZE)
return HTBOTTOMRIGHT;
else if (pt.x <= rcWindow.left + RESIZE_REGION_SIZE)
return HTLEFT;
else if (pt.x >= rcWindow.right - RESIZE_REGION_SIZE)
return HTRIGHT;
else if (pt.y <= rcWindow.top + RESIZE_REGION_SIZE)
return HTTOP;
else if (pt.y >= rcWindow.bottom - RESIZE_REGION_SIZE)
return HTBOTTOM;

return HTCAPTION; // 为了实现“鼠标按下客户区时也能移动主窗口”
//return __super::OnNcHitTest(pt);
}

BOOL CMyDlg::OnSetCursor(CWnd* pWnd, UINT nHitTest, UINT message)
{
switch (nHitTest)
{
case HTTOP:
case HTBOTTOM:
SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_SIZENS)));
return TRUE;

case HTLEFT:
case HTRIGHT:
SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_SIZEWE)));
return TRUE;

case HTTOPLEFT:
case HTBOTTOMRIGHT:
SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_SIZENWSE)));
return TRUE;

case HTTOPRIGHT:
case HTBOTTOMLEFT:
SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_SIZENESW)));
return TRUE;

default:
return __super::OnSetCursor(pWnd, nHitTest, message);
}
}

void CMyDlg::OnNcLButtonDown(UINT nHitTest, CPoint point)
{
switch (nHitTest)
{
case HTTOP:
SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_TOP, MAKELPARAM(point.x, point.y));
break;
case HTBOTTOM:
SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_BOTTOM, MAKELPARAM(point.x, point.y));
break;
case HTLEFT:
SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_LEFT, MAKELPARAM(point.x, point.y));
break;
case HTRIGHT:
SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_RIGHT, MAKELPARAM(point.x, point.y));
break;
case HTTOPLEFT:
SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_TOPLEFT, MAKELPARAM(point.x, point.y));
break;
case HTTOPRIGHT:
SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_TOPRIGHT, MAKELPARAM(point.x, point.y));
break;
case HTBOTTOMLEFT:
SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_BOTTOMLEFT, MAKELPARAM(point.x, point.y));
break;
case HTBOTTOMRIGHT:
SendMessage(WM_SYSCOMMAND, SC_SIZE | WMSZ_BOTTOMRIGHT, MAKELPARAM(point.x, point.y));
break;
default:
__super::OnNcLButtonDown(nHitTest, point);
}
}

demo下载（VS2013）  

实际上这种方法 也有一个潜在的问题，我另一篇博文中会提出其不足，并给出另一种实现resize的方法，具体请参考这篇博文