       [ ..., meta, ]  = event
       sandbox_backup  = MK.TS.DIFFPATCH.snapshot sandbox
       throw new Error "namespace collision: `S.sandbox.COLUMNS` already defined" if sandbox.COLUMNS?
-      sandbox.COLUMNS =
-        count: 2 # default number of columns in document **when using multiple columns**
-        stack: [ @_new_setting(), ]
+      @_set_sandbox_COLUMNS sandbox
       changeset = MKTS.DIFFPATCH.diff sandbox_backup, sandbox
       send [ '~', 'change', changeset, ( copy meta ), ] if changeset.length > 0
       send event

      send event
    #.......................................................................................................
    return null

#-----------------------------------------------------------------------------------------------------------
@$end_columns_with_document = ( S ) ->


#-----------------------------------------------------------------------------------------------------------
@_change_column_count = ( sandbox, event, send, column_count ) ->
  ### TAINT hotfix ###
  @_set_sandbox_COLUMNS sandbox unless sandbox.COLUMNS?
  @_stop_column_region  sandbox, event, send
  @_start_column_region sandbox, event, send, column_count

#-----------------------------------------------------------------------------------------------------------
@_restore_column_count = ( sandbox, event, send ) ->
  ### TAINT hotfix ###
  @_set_sandbox_COLUMNS sandbox unless sandbox.COLUMNS?
  @_stop_column_region  sandbox, event, send
  @_pop sandbox
  column_count = @_get_column_count sandbox
