From 8b9cf87653077d359aa7237996f8032148567c5e Mon Sep 17 00:00:00 2001
From: Jorge Moraleda <jorge.moraleda@gmail.com>
Date: Mon, 13 Apr 2020 23:43:39 -0700
Subject: [PATCH] Added an example of overriding method HasValue in wxDataView
 to show how some items may not have values for some columns.

---
 samples/dataview/dataview.cpp | 55 +++++++++++++++++++++++++++++++++++
 samples/dataview/mymodels.cpp | 12 ++++++++
 samples/dataview/mymodels.h   | 10 +++++++
 3 files changed, 77 insertions(+)

diff --git a/samples/dataview/dataview.cpp b/samples/dataview/dataview.cpp
index e7a00ab617..f6cab09aa8 100644
--- a/samples/dataview/dataview.cpp
+++ b/samples/dataview/dataview.cpp
@@ -182,6 +182,7 @@ private:
         Page_TreeStore,
         Page_VarHeight,
         Page_IndexList,
+        Page_HasValue,
         Page_Max
     };
 
@@ -713,6 +714,16 @@ MyFrame::MyFrame(wxFrame *frame, const wxString &title, int x, int y, int w, int
     sixthPanelSz->Add(button_sizer6);
     sixthPanel->SetSizerAndFit(sixthPanelSz);
 
+    // page showing that some columns don't have values for some items
+    // ---------------------------------------------------------------
+
+    wxPanel *seventhPanel = new wxPanel( m_notebook, wxID_ANY );
+
+    BuildDataViewCtrl(seventhPanel, Page_HasValue);
+
+    wxSizer *seventhPanelSz = new wxBoxSizer( wxVERTICAL );
+    seventhPanelSz->Add(m_ctrl[Page_HasValue], 1, wxGROW|wxALL, 5);
+    seventhPanel->SetSizerAndFit(seventhPanelSz);
 
     // complete GUI
     // ------------
@@ -723,6 +734,7 @@ MyFrame::MyFrame(wxFrame *frame, const wxString &title, int x, int y, int w, int
     m_notebook->AddPage(fourthPanel, "wxDataViewTreeCtrl");
     m_notebook->AddPage(fifthPanel, "Variable line height");
     m_notebook->AddPage(sixthPanel, "MyIndexListModel");
+    m_notebook->AddPage(seventhPanel, "MyDataViewHasValue");
 
     wxSizer* mainSizer = new wxBoxSizer(wxVERTICAL);
 
@@ -987,7 +999,50 @@ void MyFrame::BuildDataViewCtrl(wxPanel* parent, unsigned int nPanel, unsigned l
                                          this);
         }
         break;
+
+    case Page_HasValue:
+        {
+            wxDataViewListCtrl* lc =
+                new wxDataViewListCtrl( parent, wxID_ANY, wxDefaultPosition,
+                                        wxDefaultSize, style );
+            m_ctrl[Page_HasValue] = lc;
+
+            MyListStoreDerivedModel* page7_model = new MyListStoreHasValueModel();
+            lc->AssociateModel(page7_model);
+            page7_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" )->SetMinWidth(FromDIP(100));
+
+            wxVector<wxVariant> data;
+            for (unsigned int i=0; i<10; i++)
+            {
+                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;
     }
+
 }
 
 
diff --git a/samples/dataview/mymodels.cpp b/samples/dataview/mymodels.cpp
index 9c5ee3112b..fc60e8bb4f 100644
--- a/samples/dataview/mymodels.cpp
+++ b/samples/dataview/mymodels.cpp
@@ -626,3 +626,15 @@ bool MyListStoreDerivedModel::IsEnabledByRow(unsigned int row, unsigned int col)
     // disabled the last two checkboxes
     return !(col == 0 && 8 <= row && row <= 9);
 }
+
+// ----------------------------------------------------------------------------
+// MyListStoreHasValueModel
+// ----------------------------------------------------------------------------
+
+bool MyListStoreHasValueModel::HasValue(const wxDataViewItem &item, unsigned int col) const
+{
+    unsigned int row = GetRow( item );
+    // the diagonal entries don't have values. This is just a silly example to demonstrate the
+    // usage of overriding HasValue to specify that some columns don't have values for some items
+    return row != col;
+}
diff --git a/samples/dataview/mymodels.h b/samples/dataview/mymodels.h
index 8cab532f1f..4fbeb23e2e 100644
--- a/samples/dataview/mymodels.h
+++ b/samples/dataview/mymodels.h
@@ -266,6 +266,16 @@ public:
     virtual bool IsEnabledByRow(unsigned int row, unsigned int col) const wxOVERRIDE;
 };
 
+// ----------------------------------------------------------------------------
+// MyListStoreHasValueModel
+// ----------------------------------------------------------------------------
+
+class MyListStoreHasValueModel : public MyListStoreDerivedModel
+{
+public:
+    virtual bool HasValue(const wxDataViewItem &item, unsigned int col) const wxOVERRIDE;
+};
+
 // ----------------------------------------------------------------------------
 // MyIndexListModel
 // ----------------------------------------------------------------------------