Add wxDataViewToggleRenderer::ShowAsRadio()

This allows showing radio buttons in wxDataViewCtrl easily and natively.

Notice that this approach, adding an extra function to the existing
renderer class instead of creating some new wxDataViewRadioRenderer (see
https://github.com/wxWidgets/wxWidgets/pull/809), was finally chosen
because it is simpler to implement and, more importantly, because it
will be more natural to generalize if/when we also add a 3-state
check/radio renderer.

Closes https://github.com/wxWidgets/wxWidgets/pull/853

samples/dataview/dataview.cpp

@@ -108,6 +108,10 @@ private:
 
     void OnPrependList(wxCommandEvent& event);
     void OnDeleteList(wxCommandEvent& event);
+
+    // Third (wxDataViewListCtrl) page.
+    void OnListValueChanged(wxDataViewEvent& event);
+
     // Fourth page.
     void OnDeleteTreeItem(wxCommandEvent& event);
     void OnDeleteAllTreeItems(wxCommandEvent& event);
@@ -176,6 +180,9 @@ private:
     wxLog *m_logOld;
 
 private:
+    // Flag used by OnListValueChanged(), see there.
+    bool m_eventFromProgram;
+
     wxDECLARE_EVENT_TABLE();
 };
 
@@ -450,6 +457,8 @@ MyFrame::MyFrame(wxFrame *frame, const wxString &title, int x, int y, int w, int
     m_ctrl[2] = NULL;
     m_ctrl[3] = NULL;
 
+    m_eventFromProgram = false;
+
     SetIcon(wxICON(sample));
 
 
@@ -759,6 +768,17 @@ void MyFrame::BuildDataViewCtrl(wxPanel* parent, unsigned int nPanel, unsigned l
             page2_model->DecRef();
 
             lc->AppendToggleColumn( "Toggle" );
+
+            // We're not limited to convenience column-appending functions, it
+            // can also be done fully manually, which allows us to customize
+            // the renderer being used.
+            wxDataViewToggleRenderer* const rendererRadio =
+                new wxDataViewToggleRenderer("bool", wxDATAVIEW_CELL_ACTIVATABLE);
+            rendererRadio->ShowAsRadio();
+            wxDataViewColumn* const colRadio =
+                new wxDataViewColumn("Radio", rendererRadio, 1);
+            lc->AppendColumn(colRadio, "bool");
+
             lc->AppendTextColumn( "Text" );
             lc->AppendProgressColumn( "Progress" );
 
@@ -767,11 +787,14 @@ void MyFrame::BuildDataViewCtrl(wxPanel* parent, unsigned int nPanel, unsigned l
             {
                 data.clear();
                 data.push_back( (i%3) == 0 );
+                data.push_back( i == 7 ); // select a single (random) radio item
                 data.push_back( wxString::Format("row %d", i) );
                 data.push_back( long(5*i) );
 
                 lc->AppendItem( data );
             }
+
+            lc->Bind(wxEVT_DATAVIEW_ITEM_VALUE_CHANGED, &MyFrame::OnListValueChanged, this);
         }
         break;
 
@@ -1390,6 +1413,48 @@ void MyFrame::OnShowAttributes(wxCommandEvent& WXUNUSED(event))
     m_attributes->SetHidden(false);
 }
 
+// ----------------------------------------------------------------------------
+// MyFrame - event handlers for the third (wxDataViewListCtrl) page
+// ----------------------------------------------------------------------------
+
+void MyFrame::OnListValueChanged(wxDataViewEvent& event)
+{
+    // Ignore changes coming from our own SetToggleValue() calls below.
+    if ( m_eventFromProgram )
+    {
+        m_eventFromProgram = false;
+        return;
+    }
+
+    wxDataViewListCtrl* const lc = static_cast<wxDataViewListCtrl*>(m_ctrl[2]);
+
+    const int columnToggle = 1;
+
+    // Handle selecting a radio button by unselecting all the other ones.
+    if ( event.GetColumn() == columnToggle )
+    {
+        const int rowChanged = lc->ItemToRow(event.GetItem());
+        if ( lc->GetToggleValue(rowChanged, columnToggle) )
+        {
+            for ( int row = 0; row < lc->GetItemCount(); ++row )
+            {
+                if ( row != rowChanged )
+                {
+                    m_eventFromProgram = true;
+                    lc->SetToggleValue(false, row, columnToggle);
+                }
+            }
+        }
+        else // The item was cleared.
+        {
+            // Explicitly check it back, we want to always have exactly one
+            // checked radio item in this column.
+            m_eventFromProgram = true;
+            lc->SetToggleValue(true, rowChanged, columnToggle);
+        }
+    }
+}
+
 // ----------------------------------------------------------------------------
 // MyFrame - event handlers for the fourth page
 // ----------------------------------------------------------------------------