RFR: 8193445: JavaFX CSS is applied redundantly leading to significant performance degradation

[Ajit Ghaisas]

On Tue, 12 Nov 2019 16:52:54 GMT, Ajit Ghaisas <aghaisas at openjdk.org> wrote:

> On Tue, 12 Nov 2019 16:45:04 GMT, Ajit Ghaisas <aghaisas at openjdk.org> wrote:
> 
>> **Issue :**
>> https://bugs.openjdk.java.net/browse/JDK-8193445
>> 
>> **Background :**
>> The CSS performance improvement done in [JDK-8151756](https://bugs.openjdk.java.net/browse/JDK-8151756) had to be backed out due to functional regressions reported in [JDK-8185709](https://bugs.openjdk.java.net/browse/JDK-8185709), [JDK-8183100](https://bugs.openjdk.java.net/browse/JDK-8183100) and [JDK-8168951](https://bugs.openjdk.java.net/browse/JDK-8168951).
>> Refer to [JDK-8183100](https://bugs.openjdk.java.net/browse/JDK-8183100) for more details on this backout. 
>> 
>> **Description :**
>> This PR reintroduces the CSS performance improvement fix done in [JDK-8151756](https://bugs.openjdk.java.net/browse/JDK-8151756) while addressing the functional regressions that were reported in [JDK-8185709](https://bugs.openjdk.java.net/browse/JDK-8185709), [JDK-8183100](https://bugs.openjdk.java.net/browse/JDK-8183100) and [JDK-8168951](https://bugs.openjdk.java.net/browse/JDK-8168951).
>> For ease of review, I have made two separate commits -
>> 1) [Commit 1](https://github.com/openjdk/jfx/pull/34/commits/d964675ebc2a42f2fd6928b773819502683f2334) - Reintroduces the CSS performance improvement fix done in [JDK-8151756](https://bugs.openjdk.java.net/browse/JDK-8151756) - most of the patch applied cleanly.
>> 2) [Commit 2 ](https://github.com/openjdk/jfx/pull/34/commits/12ea8220a730ff8d98d520ce870691d54f0de00f)- fixes the functional regressions keeping performance improvement intact + adds a system test
>> 
>> **Root Cause :**
>> CSS performance improvement fix proposed in [JDK-8151756 ](https://bugs.openjdk.java.net/browse/JDK-8151756)correctly avoids the redundant CSS reapplication to children of a Parent. 
>> What was missed earlier in [JDK-8151756 ](https://bugs.openjdk.java.net/browse/JDK-8151756) fix : "CSS reapplication to the Parent itself”. 
>> This missing piece was the root cause of all functional regressions reported against [JDK-8151756](https://bugs.openjdk.java.net/browse/JDK-8151756)
>> 
>> **Fix :**
>> Fixed the identified root cause. See commit 2.
>> 
>> **Testing :**
>> 1. All passing unit tests continue to pass
>> 2. New system test (based on [JDK-8209830](https://bugs.openjdk.java.net/browse/JDK-8209830)) added in this PR - fails before this fix and passes after the fix
>> 3. System test JDK8183100Test continues to pass
>> 4. All test cases attached to regressions [JDK-8185709](https://bugs.openjdk.java.net/browse/JDK-8185709), [JDK-8183100](https://bugs.openjdk.java.net/browse/JDK-8183100) and [JDK-8168951](https://bugs.openjdk.java.net/browse/JDK-8168951) pass with this fix
>> 
>> In addition, testing by community with specific CSS performance / functionality will be helpful.
>> 
>> ----------------
>> 
>> Commits:
>>  - 12ea8220: Fix for functional regressions of JDK-8151756 + add a sytem test
>>  - d964675e: Reintroduce JDK-8151756 CSS performance fix
>> 
>> Changes: https://git.openjdk.java.net/jfx/pull/34/files
>>  Webrev: https://webrevs.openjdk.java.net/jfx/34/webrev.00
>>   Issue: https://bugs.openjdk.java.net/browse/JDK-8193445
>>   Stats: 121 lines in 5 files changed: 104 ins; 0 del; 17 mod
>>   Patch: https://git.openjdk.java.net/jfx/pull/34.diff
>>   Fetch: git fetch https://git.openjdk.java.net/jfx pull/34/head:pull/34
> 
> Reviewers: @kevinrushforth and @arapte

It will be helpful if I can get some feedback from community with additional testing apart from what is mentioned in the description.

PR: https://git.openjdk.java.net/jfx/pull/34