     @rendering = true
     @worker.postMessage ["I", [tessellation.group.n, tessellation.group.m, @cellTransforms]]
     
-    @onFinish = null
     @postponedRenderRequest = null
     
   onMessage: (e) ->

    if (@viewUpdates+=1) > @maxViewUpdatesBeforeCleanup
      @viewUpdates = 0
      @tfm = M.cleanupHyperbolicMoveMatrix @tfm

    
  modifyView: (m) ->
    @tfm = M.mul m, @tfm

    @viewUpdates = 0
    #precision falls from 1e-16 to 1e-9 in 1000 steps.
    @maxViewUpdatesBeforeCleanup = 500
    @xyt2path = makeXYT2path @tessellation.group, @appendRewrite

    @onFinish = null

  rebuildAt: (newCenter) ->
    @center = newCenter
