On Tue, 23 Jan 2024 11:51:52 GMT, Florian Kirmaier <[email protected]>
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 updated the pull request incrementally with one
> additional commit since the last revision:
>
> reverted accidental change in the .idea folder
I analysed the bug and can confirm the fix.
I summarized it in the following table.
First column is the node structure, the others the steps: update nodes, render,
update nodes, render, ...
| Nodes (L - left and R - right) / Steps | 1st -> update
Circles | 2nd -> render | 3rd -> update Lines | 4th -> render
|
|-|-|-|-|-|
|HBox |dirty
|clearDirty |dirty |clearDirty
|HBox >StackPane-L |dirty
|clearDirty |dirty |clearDirty
|HBox >StackPane-L > Group-L |dirty
|clearDirty |dirty |clearDirty
|HBox >StackPane-L > Group-L >Line-L |
| |dirty
|clearDirty
|HBox >StackPane-L > Group-L >Circle-L |dirty
|clearDirty |
|HBox >StackPane-R |dirty
|clearDirty *1 | | *3
|HBox >StackPane-R > Group-R |dirty
|dirty |dirty
|HBox >StackPane-R > Group-R > Line-R |
| |dirty *2
|dirty
|HBox >StackPane-R > Group-R > Circle-R |dirty
|dirty |dirty |dirty
*1: > no culling bits for first dirty region (Circle-L) -> skip children ->
clearDirty() is not called on children
> no root path for the second dirty region (Circle-R) -> no rendering and
root.clearDirtyTree() stops on StackPane-R (the children stay dirty: Group-R
and Circle-R)
*2: > Line-R.markTreeDirty() skips marking of further parents because Group-R
is already dirty -> the StackPane-R stays clean
*3: > the dirty regions are not collected because the StackPane-R is clean ->
Line-R is not rendered and the dirty-flag is not reset
-------
The error is that ``clearDirty()`` is not called in the second step on the
children of StackPane-R (see *1). Subsequent changes in Line-R and Circle-R are
not propagated to the root node because Group-R is already dirty (see *2) and
therefore StackPane-R remains clean. The last changes are therefore ignored in
the next rendering phase (see *3).
-------
We can simply say: **the dirty flags must be deleted on all nodes after
rendering**.
If this is true, the test can simply check this instead of screenshots or
similar.
-------------
PR Comment: https://git.openjdk.org/jfx/pull/1310#issuecomment-2079676517
