RFR: 8322619 Parts of SG no longer update during rendering - overlapping - culling - dirty [v2]

[John Hendrikx]

On Thu, 21 Dec 2023 12:57:01 GMT, Florian Kirmaier <fkirmaier at openjdk.org> wrote:

>> In some situations, a part of the SG is no longer rendered.
>> I created a test program that showcases this problem.
>> 
>> Explanation:
>> 
>> This can happen, when a part of the SG, is covered by another Node.
>> In this part, one node is totally covered, and the other node is visible.
>> 
>> When the totally covered Node is changed, then it is marked dirty and it's parent, recursively until an already dirty node is found.
>> Due to the Culling, this totally covered Node is not rendered - with the effect that the tree is never marked as Clean.
>> 
>> In this state, a Node is Dirty but not It's parent. Based on my CodeReview, this is an invalid state which should never happen.
>> 
>> In this invalid state, when the other Node is changed, which is visible, then the dirty state is no longer propagated upwards - because the recursive "NGNode.markTreeDirty" algorithm encounters a dirty node early.
>> 
>> This has the effect, that any SG changes in the visible Node are no longer rendered. Sometimes the situation repairs itself.
>> 
>> Useful parameters for further investigations:
>> -Djavafx.pulseLogger=true
>> -Dprism.printrendergraph=true
>> -Djavafx.pulseLogger.threshold=0
>> 
>> PR:
>> This PR ensures the dirty flag is set to false of the tree when the culling is used.
>> It doesn't seem to break any existing tests - but I'm not sure whether this is the right way to fix it.
>> It would be great to have some feedback on this solution - maybe guiding me to a better solution.
>> 
>> I could write a test, that just does the same thing as the test application, but checks every frame that these nodes are not dirty - but maybe there is a better way to test this.
>
> Florian Kirmaier has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
> 
>   JDK-8322619 Fix for rendering bug, related to overlap - culling - dirtynodes

The fully covered node which was dirty is now marked clean in the PR when it is culled.  Now that it is clean, what happens when it is uncovered (being careful not to change it in any other way)?  Does it get rendered correctly, or does it miss the last change made to it while it was fully covered?

If that works correctly still, then I think this is the right fix.  Culling the node is (IMHO) the same as rendering it (there is nothing to render) so it should be clean after being culled.

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PR Comment: https://git.openjdk.org/jfx/pull/1310#issuecomment-1867391189