对话框中画线

Question

画线invalidate

Answer 1

if (IsIconic())
{
CPaintDC dc(this); // 用于绘制的设备上下文 SendMessage(WM_ICONERASEBKGND, reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0); // 使图标在工作区矩形中居中
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2; // 绘制图标
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDC* pDC = GetDC();
pDC -> MoveTo(CPoint(0,0));
pDC -> LineTo(curMousePoint);
ReleaseDC(pDC);
CDialog::OnPaint();
}

Answer 2

else
{
CPaintDC dc(this); // 用于绘制的设备上下文
//    CDC* pDC = GetDC(); 不是这个DC
dc.MoveTo(CPoint(0,0));
dc. LineTo(curMousePoint);
//    CDialog::OnPaint();
}

Answer 3

把你OnPaint里的内容都删掉
重新写成下面这样就可以了void    CxxxxDlg::OnPaint()
{
    CPaintDC dc(this); 
    dc. MoveTo(CPoint(0,0));
    dc.LineTo(curMousePoint);
}

Answer 4

那就是CDC和CPaintDC的区别造成的了，谢谢了，我去查查两者的区别

Answer 5

用于无效区的DC
CPaintDC
用于有效区的DC
CClientDC
CWindowDC

Answer 6

if (IsIconic())
{
    CPaintDC dc(this); // 用于绘制的设备上下文
 
    SendMessage(WM_ICONERASEBKGND, reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0);
 
    // 使图标在工作区矩形中居中
    int cxIcon = GetSystemMetrics(SM_CXICON);
    int cyIcon = GetSystemMetrics(SM_CYICON);
    CRect rect;
    GetClientRect(&rect);
    int x = (rect.Width() - cxIcon + 1) / 2;
    int y = (rect.Height() - cyIcon + 1) / 2;
 
    // 绘制图标
    dc.DrawIcon(x, y, m_hIcon);
}
else
{
    CDC* pDC = GetDC();
    pDC -> MoveTo(CPoint(0,0));
    pDC -> LineTo(curMousePoint); //curMousePointy该对应到一个特点点
    ReleaseDC(pDC);
//    CDialog::OnPaint();  此句必须去掉
}