How to properly paint content on a wxScrolledWindow? - c++

Question

I am creating an animation timeline widget using wxWidgets.
The widget consist of a wxFrame with a wxScrolledWindow child:
I want to support horizontal zooming by changing the timeline window virtual size when the user rolls mouse middle button.
Zooming without scrolling works well. But when i start scrolling(forward and backward) things get messed up.
So to troubleshoot I decided to do a simple test:
Draw a line from the window top left corner to the bottom right corner. And the test fails!
Without scrolling -> Test pass
Zoom then scroll to right -> Test fails
Scroll back to left -> Test also fails
I have no idea of whats going on. Here my CPP code:
In .H:
class AnimationFrame : public wxFrame
{
public:
AnimationFrame();
private:
void onTimelineMouseWheel(wxMouseEvent& ev);
void onTimelinePaint(wxPaintEvent& ev);
// The scrolled window.
wxScrolledWindow* m_timelineWindow;
};
In .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));
}
Addional information:
As you certainly realised the widget is loaded from CPP using the XRC format. Here the generated code from wxFormBuilder for the widget.
XRC: https://1drv.ms/u/s!Ak_u4fVrMHMkrTe59Fuo4X2b-fRO?e=2Z0lw0
CPP: https://1drv.ms/u/s!Ak_u4fVrMHMkrTi_8w5UIkwFTl9t?e=BZBlLs