unit_binder: allow updates without triggers

Adds a helper function to allow unit binder calls that change a value
but shouldn't trigger wxevents

common/widgets/unit_binder.cpp

@@ -224,6 +224,26 @@ void UNIT_BINDER::SetValue( wxString aValue )
 }
 
 
+void UNIT_BINDER::ChangeValue( int aValue )
+{
+    ChangeValue( StringFromValue( m_units, aValue, false, m_useMils ) );
+}
+
+
+void UNIT_BINDER::ChangeValue( wxString aValue )
+{
+    if( dynamic_cast<wxTextEntry*>( m_value ) )
+        dynamic_cast<wxTextEntry*>( m_value )->ChangeValue( aValue );
+    else if( dynamic_cast<wxStaticText*>( m_value ) )
+        dynamic_cast<wxStaticText*>( m_value )->SetLabel( aValue );
+
+    if( m_allowEval )
+        m_eval.Clear();
+
+    m_unitLabel->SetLabel( GetAbbreviatedUnitsLabel( m_units, m_useMils ) );
+}
+
+
 int UNIT_BINDER::GetValue() const
 {
     wxString s;

include/widgets/unit_binder.h

@@ -75,6 +75,16 @@ public:
 
     void SetValue( wxString aValue );
 
+    /**
+     * Function ChangeValue
+     * Changes the value (in Internal Units) for the text field, taking care of units conversion
+     * but does not trigger the update routine
+     * @param aValue is the new value.
+     */
+    virtual void ChangeValue( int aValue );
+
+    void ChangeValue( wxString aValue );
+
     /**
      * Function GetValue
      * Returns the current value in Internal Units.