Use ScenePulseListener to avoid expensive recalculations?

John Hendrikx hjohn at
Tue Nov 5 06:58:32 PST 2013

Hi List,

I'm considering using a ScenePulseListener to avoid expensive 
recalculations when multiple bindings trigger an action.

My problem is this:

I like to build Views (Controls) that are dumb and expose properties 
that can be manipulated by whatever is using the View.  The View listens 
to its own Properties and adjusts its state accordingly.  Some of these 
adjustments are related (like width + height) and can be expensive when 
calculated immediately.  So I would like to mark the View as "invalid" 
and recalculate its state (if invalid) on the next Pulse.

My current use case I'm looking at is a View that wraps (amongst others) 
a TreeView.  The View exposes an ObservableList and a BooleanProperty 
that decides whether the first level of the Tree should be displayed as 
Tabs or as Nodes (which has an impact on what Nodes actually are added 
to the TreeView, and which are added as Tabs).  User code will thus 
often set a new list of nodes + change the boolean to show tabs or 
nodes.  The View currently naively has InvalidationListeners on both of 
these properties which cause TreeNodes to be created after the first 
change... then discarded and recreated after the second change by the 
user code, ie:

   view.nodesProperty().setAll(nodes);   // Recreates all Tabs/TreeNodes 
with the current value of expand top level, as we donot know another 
change might be incoming...
   view.expandTopLevelProperty().set(false);   // Recreates all 
Tabs/TreeNodes again if expand top level was changed...

This specific problem might be done in a better way, but the point 
remains, how do I avoid expensive calculations when multiple properties 
get changed one after the other by the user code?  I'm assuming that 
JavaFX controls already avoid these kinds of things, and I'd like to 
know whether using a ScenePulseListener is the way to go, or that it 
can/should be done in a different way -- examining the code for TreeView 
(and its superclasses), I couldn't find uses of ScenePulseListener...


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