[API REVIEW] RT-30576 Parent : add new public layout method, optimized to only layout this parent and it's children.

[mick.fleming]

Hi All,

this request is to add a method to javafx.scene.Parent
which only requests a re-layout on the parent and it's
children.

The current requestLayout method in Parent clears the
size cache and requests the layout of all Parents in the
containment hierarchy. This can be unnecessary if the
change is contained within the requesting node, and
there is no change to it's external size, or min/max/pref
size. A good example of this is that currently an internal
change to a table-cell could cause an entire table to
re-layout.

In order to solve this we could have an additional method in
Parent which only requests the layout of the current parent
node and it's children.

There is a significant performance gain in Table benchmarks
when this is used in cases where it is known that there are
no changes to either the cells dimensions or min/max/preferred
size.

The current proposed name for this is :
   public void requestLocalLayout()
but suggestions are welcome, especially if they
are more meaningful.

The jira can be found at :
  https://javafx-jira.kenai.com/browse/RT-30576

regards,
mick