wxScrolledWindow缩放滚动后绘制异常，如何正确绘制内容？

我使用wxWidgets开发一款动画时间轴控件，该控件包含一个wxFrame及其子控件wxScrolledWindow。我希望通过鼠标滚轮修改时间轴窗口的虚拟尺寸以实现水平缩放，无滚动时缩放功能正常，但滚动后绘制内容出现错乱。

为排查问题，我进行了简单测试：绘制一条从窗口左上角到右下角的线条，结果显示无滚动时测试正常，缩放后向右滚动、再滚回左侧时测试均失败。

代码实现 #

头文件（.H） #

class AnimationFrame : public wxFrame
{
public:
    AnimationFrame();

private:
    void onTimelineMouseWheel(wxMouseEvent& ev);
    void onTimelinePaint(wxPaintEvent& ev);

    // The scrolled window.
    wxScrolledWindow* m_timelineWindow;
};

实现文件（.CPP） #

AnimationFrame::AnimationFrame()
{
    assert(wxXmlResource::Get()->LoadFrame(this, NULL, "AnimationFrame"));

    m_timelineWindow = (wxScrolledWindow*)wxWindow::FindWindowByName("TimelineScrolledWindow", this);
    assert(m_timelineWindow);

    wxPanel* headerPanel = (wxPanel*)wxWindow::FindWindowByName("HeaderPanel", this);
    assert(headerPanel);

    // Adjust panel sizes.
    {
        headerPanel->SetMaxSize(wxSize(headerPanel->GetMaxSize().x, 40));
        m_timelineWindow->SetMaxSize(wxSize(m_timelineWindow->GetMaxSize().x, 100));
        this->SetMinSize(wxSize(this->GetSize().x, 250));
        this->SetSize(wxSize(this->GetSize().x, 250));
        this->SetMaxSize(wxSize(this->GetSize().x, 250));
    }

    // Timeline events from the scrolled window.
    m_timelineWindow->Bind(wxEVT_MOUSEWHEEL, &AnimationFrame::onTimelineMouseWheel, this);
    m_timelineWindow->Bind(wxEVT_PAINT, std::bind(&AnimationFrame::onTimelinePaint, this, std::placeholders::_1));
}


void AnimationFrame::onTimelineMouseWheel(wxMouseEvent& ev)
{
    static const nbFloat32 scrollIntensity = 1.20f;
    const nbFloat32 delta = scrollIntensity * (nbFloat32)(ev.GetWheelRotation() / ev.GetWheelDelta());

    const nbFloat32 sizeFactor = delta >= 0.0 ? delta : 1.0f / -delta;

    const wxSize currentVirtualSize = m_timelineWindow->GetVirtualSize();
    wxSize targetVirtualSize = wxSize((nbUint32)((nbFloat32)currentVirtualSize.x * sizeFactor), currentVirtualSize.y);
    targetVirtualSize.x = std::min(targetVirtualSize.x, 5000);
    targetVirtualSize.x = std::max(targetVirtualSize.x, m_timelineWindow->GetSize().x);

    m_timelineWindow->SetVirtualSize(targetVirtualSize);

    this->Refresh();
}


void AnimationFrame::onTimelinePaint(wxPaintEvent& ev)
{
    // Init the DC.
    wxPaintDC dc(m_timelineWindow);
    PrepareDC(dc);// from the scrolling sample. Doesnt seems to do anything.

    /*
    wxFont font(12, wxFONTFAMILY_SWISS, wxFONTSTYLE_NORMAL, wxFONTWEIGHT_NORMAL);
    dc.SetFont(font);
    dc.SetBackgroundMode(wxTRANSPARENT);
    dc.SetTextForeground(*wxBLACK);
    dc.SetTextBackground(*wxWHITE);
    */

    // Now draw line.
    dc.DrawLine(wxPoint(0, 0), wxPoint(m_timelineWindow->GetSize().x, m_timelineWindow->GetSize().y));
}

附加信息 #

该控件通过XRC格式从C++加载，资源由wxFormBuilder生成。

内容的提问来源于stack exchange，提问作者TheChamp