Fix wxDataViewCtrl::GetItemRect() signature in wxOSX and document it better.

The second parameter of this method should be optional, so make it so in wxOSX.

Also document what this method does exactly and the platforms under which it's
implemented.

Closes #13914.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70496 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/dataview.h

@@ -174,7 +174,8 @@ public:
   virtual bool IsExpanded(const wxDataViewItem & item) const;
 
   virtual unsigned int GetCount() const;
-  virtual wxRect GetItemRect(const wxDataViewItem& item, const wxDataViewColumn* columnPtr) const;
+  virtual wxRect GetItemRect(const wxDataViewItem& item,
+                             const wxDataViewColumn* columnPtr = NULL) const;
   virtual int GetSelectedItemsCount() const;
   virtual int GetSelections(wxDataViewItemArray& sel) const;
 

interface/wx/dataview.h

@@ -1098,7 +1098,18 @@ public:
     int GetIndent() const;
 
     /**
-        Returns item rect.
+        Returns item rectangle.
+
+        This method is currently not implemented at all in wxGTK and only
+        implemented for non-@NULL @a col argument in wxOSX. It is fully
+        implemented in the generic version of the control.
+
+        @param item
+            A valid item.
+        @param col
+            If non-@NULL, the rectangle returned corresponds to the
+            intersection of the item with the specified column. If @NULL, the
+            rectangle spans all the columns.
     */
     virtual wxRect GetItemRect(const wxDataViewItem& item,
                                const wxDataViewColumn* col = NULL) const;