drools-eclipse/org.drools.eclipse/src/main/java/org/drools/eclipse/editors/DRLRuleEditorActionContributor.java
public void setActiveEditor(IEditorPart part) {
        super.setActiveEditor( part );
        if ( part instanceof DRLRuleEditor2 ) {
            DRLRuleEditor2 p = (DRLRuleEditor2) part;
            p.setZoomComboContributionItem( zitem );
            p.setZoomInAction( zoomIn );
            p.setZoomOutAction( zoomOut );
        }
    }
public void setActiveEditor(IEditorPart part) {
        super.setActiveEditor( part );
        if ( part instanceof DRLRuleEditor2 ) {
            DRLRuleEditor2 p = (DRLRuleEditor2) part;
            p.setZoomComboContributionItem( zitem );
            p.setZoomInAction( zoomIn );
            p.setZoomOutAction( zoomOut );
        }
    }
In addition to @link org.eclipse.ui.part.MultiPageEditorActionBarContributor#setActiveEditor(org.eclipse.ui.IEditorPart)
it sets contribution items to DRLRuleEditor2 for later use when
multipageditor tabs are switched.