Refactor wxGrid code to use SetNativeHeaderColXXX() functions

Add two simple helpers: SetNativeHeaderColCount() and
SetNativeHeaderColOrder() and call the latter from the former to ensure
that the columns order is always correct when switching to the native
control.

include/wx/generic/grid.h

@@ -2382,6 +2382,12 @@ private:
     void DoSetRowSize( int row, int height );
     void DoSetColSize( int col, int width );
 
+    // These methods can only be called when m_useNativeHeader is true and call
+    // SetColumnCount() and Set- or ResetColumnsOrder() as necessary on the
+    // native wxHeaderCtrl being used. Note that the first one already calls
+    // the second one, so it's never necessary to call both of them.
+    void SetNativeHeaderColCount();
+    void SetNativeHeaderColOrder();
 
     // these sets contain the indices of fixed, i.e. non-resizable
     // interactively, grid rows or columns and are NULL if there are no fixed

src/generic/grid.cpp

@@ -2438,7 +2438,7 @@ wxGrid::SetTable(wxGridTableBase *table,
         // Notice that this must be called after setting m_table as it uses it
         // indirectly, via wxGrid::GetColLabelValue().
         if ( m_useNativeHeader )
-            GetGridColHeader()->SetColumnCount(m_numCols);
+            SetNativeHeaderColCount();
 
         m_selection = new wxGridSelection( this, selmode );
         if (checkSelection)
@@ -4569,10 +4569,7 @@ void wxGrid::RefreshAfterColPosChange()
     // and make the changes visible
     if ( m_useNativeHeader )
     {
-        if ( m_colAt.empty() )
-            GetGridColHeader()->ResetColumnsOrder();
-        else
-            GetGridColHeader()->SetColumnsOrder(m_colAt);
+        SetNativeHeaderColOrder();
     }
     else
     {
@@ -5950,7 +5947,8 @@ void wxGrid::UseNativeColHeader(bool native)
     CreateColumnWindow();
 
     if ( m_useNativeHeader )
-        GetGridColHeader()->SetColumnCount(m_numCols);
+        SetNativeHeaderColCount();
+
     CalcWindowSizes();
 }
 
@@ -8494,6 +8492,25 @@ int  wxGrid::GetRowMinimalAcceptableHeight() const
     return m_minAcceptableRowHeight;
 }
 
+void wxGrid::SetNativeHeaderColCount()
+{
+    wxASSERT_MSG( m_useNativeHeader, "no column header window" );
+
+    GetGridColHeader()->SetColumnCount(m_numCols);
+
+    SetNativeHeaderColOrder();
+}
+
+void wxGrid::SetNativeHeaderColOrder()
+{
+    wxASSERT_MSG( m_useNativeHeader, "no column header window" );
+
+    if ( !m_colAt.empty() )
+        GetGridColHeader()->SetColumnsOrder(m_colAt);
+    else
+        GetGridColHeader()->ResetColumnsOrder();
+}
+
 // ----------------------------------------------------------------------------
 // auto sizing
 // ----------------------------------------------------------------------------