void SCH_SCREENS::DeleteAllMarkers( int aMarkerType )
{
    SCH_ITEM* item;
    SCH_ITEM* nextItem;
    SCH_MARKER* marker;
    SCH_SCREEN* screen;

    for( screen = GetFirst(); screen; screen = GetNext() )
    {
        for( item = screen->GetDrawItems(); item; item = nextItem )
        {
            nextItem = item->Next();

            if( item->Type() != SCH_MARKER_T )
                continue;

            marker = (SCH_MARKER*) item;

            if( marker->GetMarkerType() != aMarkerType )
                continue;

            screen->DeleteItem( marker );
        }
    }
}