Add the possibility to disable invisible wxDataViewCtrl items.

Add new wxDataViewModel::IsEnabled() and wxDataViewListStore::IsEnabledByRow()
methods and implement support for actually disabling the items in wxOSX/Cocoa
native implementation of wxDataViewCtrl and limited support for it in the
generic version.

We need to implement this in wxGTK using GtkCellRenderer "sensitive" propriety
later.

Closes #12686.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66403 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/dataview.h

@@ -234,6 +234,13 @@ public:
         return false;
     }
 
+    // Override this if you want to disable specific items
+    virtual bool IsEnabled(const wxDataViewItem &WXUNUSED(item),
+                           unsigned int WXUNUSED(col)) const
+    {
+        return true;
+    }
+
     // define hierachy
     virtual wxDataViewItem GetParent( const wxDataViewItem &item ) const = 0;
     virtual bool IsContainer( const wxDataViewItem &item ) const = 0;
@@ -304,6 +311,12 @@ public:
         return false;
     }
 
+    virtual bool IsEnabledByRow(unsigned int WXUNUSED(row),
+                                unsigned int WXUNUSED(col)) const
+    {
+        return true;
+    }
+
 
     // helper methods provided by list models only
     virtual unsigned GetRow( const wxDataViewItem &item ) const = 0;
@@ -344,6 +357,11 @@ public:
         return GetAttrByRow( GetRow(item), col, attr );
     }
 
+    virtual bool IsEnabled(const wxDataViewItem &item, unsigned int col) const
+    {
+        return IsEnabledByRow( GetRow(item), col );
+    }
+
 
     virtual bool IsListModel() const { return true; }
 };