Update: I had a quick look, downloaded the code and for a single scroll event, there are 74 calls to updateItem. However, 69 of those are invoked via `com.jfoenix.skins.JFXListViewSkin.estimateHeight` which calls `com.jfoenix.adapters.VirtualFlowHelper.forEach` which calls into `VirtualFlow.setCell` itself.
This sounds like something to discuss with the maintainers of the library (jfoenix I believe). Maybe that library tries estimating the height of the flow as well? - Johan On Tue, Nov 22, 2022 at 5:00 PM Johan Vos <johan....@gluonhq.com> wrote: > Hi Craig, > > That boils down to the same issue I described earlier in this thread, and > that is also mentioned on https://bugs.openjdk.org/browse/JDK-8280442. I > agree the workaround does not look pretty (I suggested it myself), but the > fact that it works is not by accident. There is indeed a difference between > calling updateItem on a visible versus an invisible cell. > The boilerplate code required by the developer to distinguish between > those cases should be avoided. We can do that by e.g. passing an additional > boolean to the updateItem method, indicating if this is the accumCell or > not. But the signature of `updateItem(Object, boolean)` is already hard to > explain, especially combined with the requirement that > `super.updateItem(...)` must be called. > > - Johan > > > > On Tue, Nov 22, 2022 at 1:22 PM Craig Raw <craig...@gmail.com> wrote: > >> I encountered the same problem and described my solution here: >> https://mail.openjdk.org/pipermail/openjfx-dev/2022-July/034764.html >> >> It's not pretty but it does seem to work. >> >> On Tue, Nov 22, 2022 at 1:18 PM Glavo <zjx001...@gmail.com> wrote: >> >>> We created an advanced list with titles, subtitles, icons, and tags, and >>> updated these contents in the updateItem. >>> >>> I took a screenshot of it and uploaded it as a comment to GitHub next to >>> the relevant code: >>> >>> >>> https://github.com/huanghongxun/HMCL/pull/1849/commits/4f8cde63acf959d85416b706acf22f9b3c80ec63#r1029184905 >>> >>> It worked well in the past, but in JavaFX 17, it was so slow that it >>> blocked the UI thread for a few seconds, making the operating system think >>> that the program did not respond.‘ >>> >>> I improved the updateItem to make it ten times faster, but even so, it >>> is still not as smooth as before, and there will be an obvious FPS drop. >>> >>> If possible, please check our code on GitHub through the above link. >>> >>> It is difficult to continue to optimize the updateItem method. Even if I >>> use a Map to cache nodes created for elements, it will not become faster. >>> Are we using it in the wrong way? >>> >>> On Tue, Nov 22, 2022 at 4:48 PM Johan Vos <johan....@gluonhq.com> wrote: >>> >>>> Hi Glavo, >>>> >>>> There are more frequent calls to updateItem() since the VirtualFlow >>>> tries to gradually improve its estimation how large the total list size is >>>> (rather than assuming all cells have the same size). The major point is >>>> that if you override updateItem, it should not do more than strictly needed >>>> (e.g. don't create a Node etc). That method should return as fast as >>>> possible. >>>> >>>> There are many completely different usecases for VirtualFlow in >>>> general, and it's not trivial to come up with a single implementation that >>>> deals "best" with all usecases. Therefore, I recently solicited for >>>> feedback and it might be good if you can give yours too? >>>> See >>>> https://mail.openjdk.org/pipermail/openjfx-dev/2022-September/035851.html >>>> for the start of the discussion. >>>> >>>> - Johan >>>> >>>> >>>> On Tue, Nov 22, 2022 at 9:24 AM Glavo <zjx001...@gmail.com> wrote: >>>> >>>>> Hi, >>>>> >>>>> I'm one of the maintainers of the open source project HMCL (Hello! >>>>> Minecraft Launcher*)*. This is a Minecraft launcher based on JavaFX. >>>>> >>>>> In the past year, we have received a lot of feedback on performance >>>>> problems. Through performance analysis, I noticed that from JavaFX 17 >>>>> ea+8, >>>>> the performance of list scrolling is terrible. >>>>> >>>>> I analyzed the method calls and noticed that the updateItem method of >>>>> ListCell is called 8 times more frequently in JavaFX 17 than in JavaFX 16. >>>>> >>>>> I guess this is due to the following commit: >>>>> >>>>> >>>>> https://github.com/openjdk/jfx/commit/8e547571fb3d40df843c27fc11921b5d4765c481 >>>>> >>>>> I wonder if this is a bug? >>>>> >>>>> Best regards, >>>>> Glavo >>>>> >>>>>
