求助：如何实现按下鼠标左键拖动对话框移动的功能？

[gxqcdit]

用VS2003实现功能：在一个非模态对话框客户区（对话框没有TITLE，BORDER类型为NONE）按下鼠标左键然后移动鼠标从而拖动该对话框，我用如下代码，实现的效果可以拖动该对话框，但在拖动的过程中对话框不停的闪烁和抖动，为何？


void CShowWnd::OnLButtonDown(UINT nFlags, CPoint point)
{
m_bLBPressed = true;

m_nPrePtX = point.x;
m_nPrePtY = point.y;

CDialog::OnLButtonDown(nFlags, point);
}

void CShowWnd::OnLButtonUp(UINT nFlags, CPoint point)
{
m_bLBPressed = false;
CDialog::OnLButtonUp(nFlags, point);
}
void CShowWnd::OnMouseMove(UINT nFlags, CPoint point)
{
if (m_bLBPressed)
{
CRect rct;
::GetWindowRect(this->GetSafeHwnd(), &rct);
int nSpanX = point.x - m_nPrePtX;
int nSpanY = point.y - m_nPrePtY;

::SetWindowPos(this->GetSafeHwnd(), HWND_TOP, rct.left+nSpanX, rct.top+nSpanY, rct.Width(), rct.Height(), SWP_FRAMECHANGED);

m_nPrePtX = point.x;
m_nPrePtY = point.y;
}

CDialog::OnMouseMove(nFlags, point);
}

请高手们赐教啊。

[gxqcdit]

CShowWnd类就是该非模态对话框类，为什么会抖动呢？

[gxqcdit]

呵呵，我搜索了以前的帖子，解决了 void CShowWnd::OnLButtonDown(UINT nFlags, CPoint point) { // TODO: Add your message handler code here and/or call default PostMessage(WM_NCLBUTTONDOWN,HTCAPTION,MAKELPARAM(point.x,point.y)); CDialog::OnLButtonDown(nFlags, point); }

[菜牛]

响应WM_NCHITTEST消息返回HTCAPTION即可。