I was able to reproduce this bug while using xtrace and confirmed that the _NET_WM_FRAME_DRAWN message is not being sent. BTW it takes a lot longer to reproduce this with xtrace.
I’ve written a standalone GTK 3.0 application that demonstrates the problem. I’ll attach it to the JBS ticket. So far I’ve only been able to reproduce this on Ubuntu 24 LTS with Xorg as the backend. When I run Ubuntu 24 under Wayland I can’t get it to reproduce. In Ubuntu 26 Wayland is the only option so I can’t reproduce the bug there, either. The frame lock freezing and thawing is internal to GDK and looking at the sources I don’t see any way to thaw it externally. Martin > On Aug 16, 2026, at 3:19 PM, Thiago Milczarek Sayão <[email protected]> > wrote: > > The issue cannot be reproduced when running with GDK_SYNCHRONIZE=1 (not > recommended; used for testing purposes only). > > I've tried a few workarounds, but so far, none of them have been successful. > > > > Em dom., 16 de ago. de 2026 às 02:41, Christopher Schnick < > [email protected]> escreveu: > >> Would there be any way to guard against the bug from the JavaFX-side so >> that an invisible popup won't be shown when it happens? Doesn't have to >> be pretty, just to avoid the most glaring issue >> >> On 16/08/2026 02:56, Thiago Milczarek Sayão wrote: >>> Hi, >>> >>> It seems that this is a bug in Mutter. >>> >>> I tried disabling frame synchronization using >>> gdk_x11_window_set_frame_sync_enabled(), but the issue still occurs. >>> >>> I also tried forcing an Expose event after the popup was mapped, but that >>> did not solve the problem either. >>> >>> The popup window is mapped correctly, but occasionally it is not rendered >>> on screen. >>> >>> >>> See (the video shows one run, but i did many with the same result): >>> >>> youtube.com/watch?v=1LB2OLrYex8&feature=youtu.be >>> >>> Xephyr :100 >>> >>> DISPLAY=:100 java @/home/tsayao/jfx/build/run.args AutoPopupTest.java >>> >>> Test 1: >>> No window manager - bug does not happen >>> >>> Test 2: >>> kwin - bug does not happen >>> DISPLAY=:100 dbus-run-session kwin_x11 --replace >>> >>> Test 3: >>> mutter - bug happens >>> DISPLAY=:100 dbus-run-session -- mutter --x11 >>> >>> -- Thiago. >>> >>> >>> >>> Em ter., 11 de ago. de 2026 às 20:18, Martin Fox <[email protected] >>> >>> escreveu: >>> >>>> For those of you who haven’t looked at the bug report, it has to do with >>>> GDK expecting the windowing system to send it a _NET_WM_FRAME_DRAWN >> message >>>> but the message never arrives. If this is something you have any >> experience >>>> with feel free to jump in and investigate (because I’m at a loss). >>>> >>>> It looks like we’re not the only one seeing this. I ran across a thread >>>> detailing how GVim sometimes freezes (vim/vim repository on GitHub, >> issue >>>> #12671) and they also concluded it was due to GDK not receiving this >>>> message. The Discourse discussion contains more information (link in the >>>> JBS ticket). They were not able to resolve the problem. >>>> >>>> Martin >>>> >>>>> On Aug 10, 2026, at 11:59 AM, Andy Goryachev < >> [email protected]> >>>> wrote: >>>>> I think this scenario warrants bumping the issue to P3. >>>>> >>>>> -andy >>>>> >>>>> >>>>> From: PavelTurk <[email protected]> >>>>> Date: Sunday, August 9, 2026 at 23:55 >>>>> To: [email protected] <[email protected]> >>>>> Subject: [External] : Using JavaFX on Linux can be dangerous >>>>> >>>>> Hi everyone, >>>>> >>>>> I would like to warn everyone and provide some feedback regarding the >>>>> use of JavaFX on Linux. We developed a small application and gave it to >>>>> a small number of the customer’s employees for testing. The application >>>>> was tested on both Linux and Windows. >>>>> >>>>> We encountered serious problems on Linux. Due to bug JDK-8371781, popup >>>>> windows are not displayed to the user, but they are still present in >> the >>>>> scene. As a result, a user can click on elements in these popups >> without >>>>> being able to see them, potentially triggering actions that they >>>>> absolutely should not be able to perform. >>>>> >>>>> Therefore, I decided to bring this issue to the attention of the JavaFX >>>>> developers and warn others about the potential safety implications of >>>>> using JavaFX on Linux. >>>>> >>>>> Best regards, Pavel >>>> >>
