wxRendererNative::Get does not work with updated wxwidgets 3.1.5 - c++

Question

I came across the following MRE that does not work anymore as it generates the error given below. The user who wrote this MRE at the time claimed that this works but after trying this example now, i get the error given below. My question is that how can I make the MRE working again. That is how to get rid of this error. Also, I want to know why it doesn't work anymore.
Note also that this example was written and provided here by #NewPagodi.
#ifdef WX_PRECOMP
#include "wx_pch.h"
#endif
#ifdef __BORLANDC__
#pragma hdrstop
#endif //__BORLANDC__
#include <wx/dcmemory.h>
#include <wx/renderer.h>
#include <wx/vlbox.h>
#include <wx/sizer.h>
#include <wx/panel.h>
#include <wx/statusbr.h>
#include <wx/frame.h>
#include <wx/app.h>
#include <set>
#include "lock.xpm"
#include "trash.xpm"
wxDECLARE_EVENT(myEVT_VLIST_BUTTON_CLICK, wxCommandEvent);
wxDECLARE_EVENT(myEVT_VLIST_CHECK_CLICK, wxCommandEvent);
class myVListBox:public wxVListBox
{
public:
myVListBox(wxWindow *parent, wxWindowID id=wxID_ANY, const wxPoint &pos=wxDefaultPosition, const wxSize &size=wxDefaultSize, long style=0, const wxString &name=wxVListBoxNameStr);
virtual void OnDrawItem (wxDC &dc, const wxRect &rect, size_t n) const;
virtual wxCoord OnMeasureItem (size_t n) const;
private:
void OnVListLeftUp( wxMouseEvent& event );
wxBitmap CheckPlainBitmap;
wxBitmap CheckCheckedBitmap;
wxBitmap TrashBitmap;
wxBitmap LockBitmap;
//configurable
int CheckSide;
int CheckTextSide;
int ButtonSide;
//computed
int TextStart;
int CheckEnd;
int ButtonWidth;
int BoxHeight;
int CheckGap;
int TextGap;
int ButtonGap;
std::set<int> selected;
};
wxDEFINE_EVENT(myEVT_VLIST_BUTTON_CLICK, wxCommandEvent);
wxDEFINE_EVENT(myEVT_VLIST_CHECK_CLICK, wxCommandEvent);
myVListBox::myVListBox(wxWindow *parent, wxWindowID id, const wxPoint &pos, const wxSize &size, long style, const wxString &name)
:wxVListBox(parent, wxID_ANY, pos, size, style, name)
{
wxDelegateRendererNative rn = wxRendererNative::Get();
wxSize sz = rn.GetCheckBoxSize(this);
CheckPlainBitmap = wxBitmap(sz);
CheckCheckedBitmap = wxBitmap(sz);
wxMemoryDC temp_dc;
temp_dc.SelectObject(CheckPlainBitmap);
rn.DrawCheckBox(this, temp_dc, wxRect(0,0,sz.GetWidth(),sz.GetHeight()),wxCONTROL_NONE );
temp_dc.SelectObject(CheckCheckedBitmap);
rn.DrawCheckBox(this, temp_dc, wxRect(0,0,sz.GetWidth(),sz.GetHeight()),wxCONTROL_CHECKED );
temp_dc.SelectObject(wxNullBitmap);
CheckSide=5;
CheckTextSide=5;
ButtonSide=5;
TrashBitmap=wxBitmap(trash_xpm);
LockBitmap=wxBitmap(lock_xpm);
//computed
CheckEnd=CheckSide+sz.GetX();
TextStart=CheckEnd+CheckTextSide;
ButtonWidth=TrashBitmap.GetWidth();
wxSize textSz = GetTextExtent("Test");
//Compute the box heights and the gaps
BoxHeight = sz.GetHeight();
if(textSz.GetHeight()>BoxHeight)
{
BoxHeight=textSz.GetHeight();
}
if(TrashBitmap.GetHeight()>BoxHeight)
{
BoxHeight=TrashBitmap.GetHeight();
}
BoxHeight+=4;
CheckGap=(BoxHeight-sz.GetHeight())/2;
TextGap=(BoxHeight-textSz.GetHeight())/2;
ButtonGap=(BoxHeight-TrashBitmap.GetHeight())/2;
Bind( wxEVT_LEFT_UP, &myVListBox::OnVListLeftUp , this );
}
wxCoord myVListBox::OnMeasureItem (size_t n) const
{
return BoxHeight;
}
void myVListBox::OnDrawItem(wxDC &dc, const wxRect &rect, size_t n) const
{
int textLeft=rect.GetLeft()+TextStart;
int textTop=rect.GetTop()+TextGap;
int checkLeft=rect.GetLeft()+CheckSide;
int checkTop=rect.GetTop()+CheckGap;
int buttonLeft=rect.GetRight()-ButtonWidth-ButtonSide;
int buttonTop=rect.GetTop()+ButtonGap;
if(selected.find(n) == selected.end())
{
dc.DrawBitmap( CheckPlainBitmap, checkLeft, checkTop );
}
else
{
dc.DrawBitmap( CheckCheckedBitmap, checkLeft, checkTop );
}
if(IsSelected(n) )
{
wxColour c= dc.GetTextForeground();
dc.SetTextForeground(*wxWHITE);
dc.DrawText( wxString::Format("entry %d",n), textLeft, textTop );
dc.SetTextForeground(c);
}
else
{
dc.DrawText( wxString::Format("entry %d",n), textLeft, textTop );
}
if(n%3==1)
{
dc.DrawBitmap( TrashBitmap, buttonLeft,buttonTop, true );
}
else
{
dc.DrawBitmap( LockBitmap, buttonLeft,buttonTop, true );
}
}
void myVListBox::OnVListLeftUp( wxMouseEvent& event )
{
int item = VirtualHitTest(event.GetY());
if(item==wxNOT_FOUND)
{
return;
}
wxRect r=GetItemRect(item);
bool OnButton(false);
if( CheckSide<=event.GetX() && event.GetX()<=CheckEnd )
{
if(r.GetTop()+CheckGap <= event.GetY() &&event.GetY() <=r.GetBottom()-CheckGap )
{
std::set<int>::iterator it= selected.find(item);
if( it == selected.end() )
{
selected.insert(item);
}
else
{
selected.erase(it);
}
RefreshRow(item);
wxCommandEvent event2(myEVT_VLIST_CHECK_CLICK,GetId());
event2.SetEventObject(this);
event2.SetInt(item);
event2.SetExtraLong(it == selected.end());
ProcessWindowEvent(event2);
}
}
else if( r.GetRight()-ButtonSide-ButtonWidth<=event.GetX() && event.GetX()<=r.GetRight()-ButtonSide )
{
if(r.GetTop()+ButtonGap <= event.GetY() &&event.GetY() <=r.GetBottom()-ButtonGap )
{
wxCommandEvent event2(myEVT_VLIST_BUTTON_CLICK,GetId());
event2.SetEventObject(this);
event2.SetInt(item);
ProcessWindowEvent(event2);
}
}
event.Skip();
}
class vlistFrame : public wxFrame
{
public:
vlistFrame( wxWindow* parent, wxWindowID id = wxID_ANY, const wxString& title = wxT("myVListBox demo"), const wxPoint& pos = wxDefaultPosition, const wxSize& size = wxSize( 481,466 ), long style = wxDEFAULT_FRAME_STYLE|wxTAB_TRAVERSAL );
private:
void OnVListButton(wxCommandEvent& event);
void OnVListCheck(wxCommandEvent& event);
myVListBox* m_vlist;
};
vlistFrame::vlistFrame( wxWindow* parent, wxWindowID id, const wxString& title, const wxPoint& pos, const wxSize& size, long style ) : wxFrame( parent, id, title, pos, size, style )
{
wxPanel* m_panel1 = new wxPanel( this, wxID_ANY, wxDefaultPosition, wxDefaultSize, wxTAB_TRAVERSAL );
wxBoxSizer* bSizer2 = new wxBoxSizer( wxVERTICAL );
m_vlist=new myVListBox(m_panel1);
m_vlist->SetItemCount (20);
bSizer2->Add( m_vlist, 1, wxALL|wxEXPAND, 5 );
m_panel1->SetSizer( bSizer2 );
m_panel1->Layout();
bSizer2->Fit( m_panel1 );
CreateStatusBar( 2, wxST_SIZEGRIP, wxID_ANY );
// Connect Events
m_vlist->Bind( myEVT_VLIST_BUTTON_CLICK, &vlistFrame::OnVListButton , this );
m_vlist->Bind( myEVT_VLIST_CHECK_CLICK, &vlistFrame::OnVListCheck , this );
}
void vlistFrame::OnVListButton(wxCommandEvent& event)
{
SetStatusText( wxString::Format("Item %d button clicked",event.GetInt()),1);
}
void vlistFrame::OnVListCheck(wxCommandEvent& event)
{
SetStatusText( wxString::Format("Item %d check clicked %s",event.GetInt(),
(event.GetExtraLong()?"true":"false")),1);
}
class vlistApp : public wxApp
{
public:
virtual bool OnInit()
{
vlistFrame* frame = new vlistFrame(0L);
frame->Show();
return true;
}
};
wxIMPLEMENT_APP(vlistApp);
The above produces the following error:
/home/user/Documents/folder/somefo/anj/sno/vlistMain.cpp: In constructor ‘myVListBox::myVListBox(wxWindow*, wxWindowID, const wxPoint&, const wxSize&, long int, const wxString&)’:
/home/user/Documents/folder/somefo/anj/sno/vlistMain.cpp:10:57: error: ‘wxDelegateRendererNative::wxDelegateRendererNative(const wxDelegateRendererNative&)’ is private within this context
wxDelegateRendererNative rn = wxRendererNative::Get();
^
In file included from /usr/local/include/wx-3.1/wx/memory.h:14:0,
from /usr/local/include/wx-3.1/wx/object.h:19,
from /usr/local/include/wx-3.1/wx/dc.h:18,
from /usr/local/include/wx-3.1/wx/dcmemory.h:14,
from /home/user/Documents/folder/somefo/anj/sno/../../headers/sno/vlistMain.h:14,
from /home/user/Documents/folder/somefo/anj/sno/vlistMain.cpp:2:
/usr/local/include/wx-3.1/wx/renderer.h:594:5: note: declared private here
wxDECLARE_NO_COPY_CLASS(wxDelegateRendererNative);
^
/home/user/Documents/folder/somefo/anj/sno/vlistMain.cpp:10:57: error: use of deleted function ‘wxDelegateRendererNative::wxDelegateRendererNative(const wxDelegateRendererNative&)’
wxDelegateRendererNative rn = wxRendererNative::Get();
^
In file included from /usr/local/include/wx-3.1/wx/memory.h:14:0,
from /usr/local/include/wx-3.1/wx/object.h:19,
from /usr/local/include/wx-3.1/wx/dc.h:18,
from /usr/local/include/wx-3.1/wx/dcmemory.h:14,
from /home/user/Documents/folder/somefo/anj/sno/../../headers/sno/vlistMain.h:14,
from /home/user/Documents/folder/somefo/anj/sno/vlistMain.cpp:2:
/usr/local/include/wx-3.1/wx/renderer.h:594:5: note: declared here
wxDECLARE_NO_COPY_CLASS(wxDelegateRendererNative);
^
In file included from /home/user/Documents/folder/somefo/anj/sno/../../headers/sno/vlistMain.h:15:0,
from /home/user/Documents/folder/somefo/anj/sno/vlistMain.cpp:2:
/usr/local/include/wx-3.1/wx/renderer.h:428:5: note: after user-defined conversion: wxDelegateRendererNative::wxDelegateRendererNative(wxRendererNative&)
wxDelegateRendererNative(wxRendererNative& rendererNative)

Answer 1

The problem is that wxRendererNative::Get() returns a reference (see documentation) to the renderer you intend to use for drawing, but you try to create a new renderer as local variable. Moreover, it returns wxRendererNative&, but you try to create wxDelegateRendererNative (which is derived from wxRendererNative), so the type of new renderer is different, and in its documentation you can see that it doesn't have appropriate constructors to be constructed from wxRendererNative. And even if such constructor was available, the copied renderer could behave differently than what you wanted (e.g. draw something in its own state/buffer and not copy that to original one). So, you should use the returned reference instead by, e.g., saving it to local reference variable and using it to access original native renderer:
wxRendererNative& rn = wxRendererNative::Get();
// ...
P.S. Note that the previous version of this answer was to save returned reference to wxDelegateRendererNative& rn, which was wrong (thanks VZ.) because renderer could have different dynamic type than wxDelegateRendererNative, and wouldn't even compile since initializing derived lvalue reference to base object is not allowed in reference initialization (except when conversion from base to derived lvalue reference is defined, which is not the case here). Also, note that delegate renderer is needed only when you try to define your own renderer with limited additional functionality and delegate everything else (via inheritance from wxDelegateRendererNative) to other renderer (which is passed as constructor parameter to delegate; see example). If your renderer was implemented this way and you know dynamic type of renderer at compile time, you can do explicit reference cast using static_cast and actually use wxDelegateRendererNative& (beware of UB if cast is unsuccessful), but in this case using actual type of renderer (e.g. MyRendererNative&) will be more likely to help optimizer 'devirtualize' virtual method calls through this reference (which is the only reason I can think of to do downcast in this situation).