Save specified, not actual, col width in wxPersistentDataViewCtrl

This is more correct as saving the current width of the last column
would prevent the user from shrinking it under the last automatically
set size, i.e. the UI behaviour would change after restarting the
program, which shouldn't be the case.

Doing this required making WXGetManuallySetWidth(), which previously
existed in the generic version only, available in all ports, so do it
and also rename it to WXGetSpecifiedWidth() in the process, as this
seems a somewhat better name (it doesn't have to be manually specified,
i.e. it could also be done by the program itself or even implicitly by
wxPersistentDataViewCtrl).

Don't make this function public, at least for now, because it's not
clear how could it be useful and it might still need to be changed to
behave differently in the other ports.

include/wx/dataview.h

@@ -514,6 +514,12 @@ public:
     virtual void SetBitmap( const wxBitmap& bitmap ) wxOVERRIDE { m_bitmap = bitmap; }
     virtual wxBitmap GetBitmap() const wxOVERRIDE { return m_bitmap; }
 
+    // Special accessor for use by wxWidgets only returning the width that was
+    // explicitly set, either by the application, using SetWidth(), or by the
+    // user, resizing the column interactively. It is usually the same as
+    // GetWidth(), but can be different for the last column.
+    virtual int WXGetSpecifiedWidth() const { return GetWidth(); }
+
 protected:
     wxDataViewRenderer      *m_renderer;
     int                      m_model_column;

include/wx/generic/dataview.h

@@ -145,7 +145,7 @@ public:
     // user interactively.
     void WXOnResize(int width);
 
-    int WXGetManuallySetWidth() const;
+    virtual int WXGetSpecifiedWidth() const wxOVERRIDE;
 
 private:
     // common part of all ctors

include/wx/persist/dataview.h

@@ -61,7 +61,15 @@ public:
             SaveValue(columnPrefix + wxPERSIST_DVC_HIDDEN, column->IsHidden());
             SaveValue(columnPrefix + wxPERSIST_DVC_POS,
                       control->GetColumnPosition(column));
-            SaveValue(columnPrefix + wxPERSIST_DVC_WIDTH, column->GetWidth());
+
+            // We take special care to save only the specified width instead of
+            // the currently used one. Usually they're one and the same, but
+            // they can be different for the last column, whose size can be
+            // greater than specified, as it's always expanded to fill the
+            // entire control width.
+            const int width = column->WXGetSpecifiedWidth();
+            if ( width > 0 )
+                SaveValue(columnPrefix + wxPERSIST_DVC_WIDTH, width);
 
             // Check if this column is the current sort key.
             if ( column->IsSortKey() )

src/generic/datavgen.cpp

@@ -217,7 +217,7 @@ void wxDataViewColumn::WXOnResize(int width)
     m_owner->OnColumnResized();
 }
 
-int wxDataViewColumn::WXGetManuallySetWidth() const
+int wxDataViewColumn::WXGetSpecifiedWidth() const
 {
     // Note that we need to return valid value even if no width was initially
     // specified, as otherwise the last column created without any explicit
@@ -5130,7 +5130,7 @@ void wxDataViewMainWindow::UpdateColumnSizes()
         // reduce it until this size if it's currently wider, so this
         // comparison needs to be strict).
         if ( availableWidth < wxMax(lastCol->GetMinWidth(),
-                                    lastCol->WXGetManuallySetWidth()) )
+                                    lastCol->WXGetSpecifiedWidth()) )
         {
             return;
         }
@@ -5319,7 +5319,7 @@ void wxDataViewCtrl::OnDPIChanged(wxDPIChangedEvent& event)
             minWidth = minWidth * event.GetNewDPI().x / event.GetOldDPI().x;
         m_cols[i]->SetMinWidth(minWidth);
 
-        int width = m_cols[i]->WXGetManuallySetWidth();
+        int width = m_cols[i]->WXGetSpecifiedWidth();
         if ( width > 0 )
             width = width * event.GetNewDPI().x / event.GetOldDPI().x;
         m_cols[i]->SetWidth(width);