On 3/6/2015 5:42 PM, Semyon Sadetsky wrote:
Hi,
please review a fix for JDK9.
bug: https://bugs.openjdk.java.net/browse/JDK-8013566
webrev:
http://cr.openjdk.java.net/~alexsch/semyon-sadetsky/8013566/webrev.00/
User got here an infinite loop inside GroupLayout's auto-gap-insertion
mechanism that was triggered by getPreferredSize() call upon the
JFrame.pack().
The GroupLayout has not trivial algorithm and its code is really
nontransparent. The aim of its auto-preferred-gap-insertion algorithm
is inserting gaps between the container components. This allows user
to not specify gaps manually for convenience.
In the considered scenario user relays on the
auto-preferred-gap-insertion except for one place where he specifies
the preferred gap manually. Moreover this manual preferred gap is
inserted not at the leading position but at the trail. That is
specifically the case when the algorithm fails.
The thing is that the auto-preferred-gap-insertion routine
insertAutopadding() cannot distinguish its auto inserted preferred
gaps from manual preferred gaps because it uses the "instance of"
check but all those gaps are instances of the same
AutoPreferredGapSpring class.
What is the reason that the class of the manual inserted gap is
AutoPreferredGapSpring and not GapSpring?
Thanks,
Alexandr.
Also the insertAutopadding() does not insert gaps at trailing
positions but only at leading. More precisely the trailing
AutoPreferredGapSpring object left from the child level group (which
insertAutopadding() is called recursively) is ignored on the parent
group level and parent's insertAutopadding() inserts a new leading
AutoPreferredGapSpring object connected to the last component of the
child level group, but this in its turn makes a spring counter value
(which serves as a loop exit flag) incorrect. As result preferred gaps
are added infinitely on this position.
The fix introduces a check that tests if the AutoPreferredGapSpring
related the current leading component is already created as a trailing
gap on the child group level, and if it is this trailing
AutoPreferredGapSpring is used to setup the source and new
AutoPreferredGapSpring object is not created.
--Semyon
