Usecase for needsLayout property?

John Hendrikx hjohn at
Wed Jun 5 02:29:25 PDT 2013

I'm having a bit of a chicken-egg problem with regards to some 
dynamically sized components I'm displaying in my application.

I have a group with a title that wraps some content and displays a title 
above it -- the entire group, including the title must be hidden and 
unmanaged when the content it is wrapping is empty, here it is in code:

protected Pane createTitledBlock(final String title, final Node content, 
final BooleanExpression visibleCondition) {
return new VBox() {{
getChildren().add(new Label(title) {{
if(visibleCondition != null) {

When the content becomes available and visibleCondition gets toggled to 
true, the content part of the titled group is not yet laid out. This 
causes the title to be visible without any content briefly until a 
layout pass occurs.

- Group with title is hidden/unmanaged
- The content gets updated and visibleCondition is set to true
- Group with title becomes visible/managed
- Briefly an empty group with title is displayed
- Layout occurs, group with title gets resized

Now, I'm thinking of playing with the needsLayout property and delaying 
the making visible/managed of the titled group until needsLayout is 
false... however, I have a feeling that won't work as an 
unmanaged/hidden group is probably not gonna participate in the layout, 
resulting in needsLayout never becoming false again as it is not 
visible/managed yet...

Any ideas how I could resolve this, and have the group with title only 
visible and managed when it is properly laid out?

Also, has any progress in general been made with regards to 
hidden/unmanaged controls and determining their expected size when 
they're made visible/managed?


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