RFR: 8246745: ListCell/Skin: misbehavior on switching skin

[Jeanette Winzenburg]

On Tue, 16 Jun 2020 05:50:43 GMT, Ambarish Rapte <arapte at openjdk.org> wrote:

>> hmm, do you mean a list with height of one cell only?
>> 
>> My experiment (having counters per instance and per computeXXHeight), logs 1 (or 2) for computePref with fixed size and
>> 5 (1 each for min/max and 3 for pref) without fixedSize per layout pass. So it's 5* access of either the local field or
>> the listView method .. wouldn't expect any problems, but then assumed performance is reading in coffee ground :)  Let's
>> hope there are some metrics to use :)
>
>> hmm, do you mean a list with height of one cell only?
> 
> Yes, List with one cell height.
> In continuation to my previous comment, looks like 8 of the first 23 calls when window is displayed for the first time
> are NOT for the one visible cell. These 8 calls are for some intermediate cell. I added a single counter for all three
> `computeXXHeight` methods and verified with a list of height of one cell. When `fixedCellSize` is not set, total
> combined number of calls for a cell are, 1)   15, when Stage is displayed for the first time.(+8 for an intermediate
> cell, not sure why) 2)   5, when the list item is selected.
> 3)   5, when the Window is resized.

something similar as I'm seeing - that's good :) Uploaded my [play
code](https://gist.github.com/kleopatra/37ac1bffa0e2ad7580cd55344237cdca) to gist: the idea is to do something (like
f.i. moving the selection), then press f1 to log the calls to each cell (the skin has a final instance counter and
counters for calling the compute methods).

As much fun as this is (really like to dig until I'm dirty all over :) - at the end of the day we'll need some
measurements (doing these is not so much fun, still hoping something already available)

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PR: https://git.openjdk.java.net/jfx/pull/251