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StackOverflowException when OSR browser gains Focus #489

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StackOverflowException when OSR browser gains Focus#489
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@nprice-flextrade
nprice-flextrade
opened on Dec 4, 2024

Describe the bug
While running a JCEF-based application, I noticed some unexpected messages being written to the STDERR stream (System.err)

These messages simply read Exception in thread "AWT-EventQueue-0"

After a significant amount of effort, I tracked these down to an unreported StackOverflowError, being triggered by CefClient.onGotFocus

To Reproduce
Steps to reproduce the behavior:

  1. Use the Simple example application
  2. Update useOsr to true in the main method of the MainFrame class
  3. Run the app as normal (ensuring the necessary --add-exports parameters are included for Java 9+)
  4. Observe the System.err log output contains multiple instances of Exception in thread "AWT-EventQueue-0"

Expected behavior
We shouldn't see unexpected errors...

Versions (please complete the following information):

  • OS: Windows
  • Java Version: OpenJDK 17
  • JCEF Version: 99c2f7a
  • CEF Version: 127.3.1

Additional context
Putting a breakpoint in CefClient.onGotFocus reveals that this method is triggered repeatedly, with the following stack:

onGotFocus:461, CefClient (org.cef) [39]
N_SetFocus:-1, CefBrowser_N (org.cef.browser)
setFocus:497, CefBrowser_N (org.cef.browser)
onGotFocus:461, CefClient (org.cef) [38]
...

Activity

nprice-flextrade
added
bugBug report
on Dec 4, 2024

Samool1 commented on Apr 28, 2025

@Samool1
Samool1
on Apr 28, 2025

Also running into this. Happens when using the same version as in the original issue, but also tried it with:

  • JCEF commit: 1770317
  • CEF version: 132.3.1+g144febe+chromium-132.0.6834.83

While not happening at the exact same time as the exception message, we are having issues with some random crashing on Linux some time after minimizing the LWJGL/GLFW window, which may be related.

We're using a custom CefBrowserOsr implementation that doesn't care about the window implementation itself, only handling rendering through onPaint() calls, but maybe there's something deeper down that watches for focus changes in the process?

We use createBrowser passing 0l as windowHandle, if that matters.

I tried overriding CefBrowser_N.setFocus and making it do nothing, as we don't really care about properly detecting focus in our OSR implementation. That did remove the exception message, but the Linux crashes remain.

KlemenDEV commented on Nov 3, 2025

@KlemenDEV
KlemenDEV
on Nov 3, 2025

I can confirm this issue. Is there any updates on this? OSR mode keeps spamming console logs with "exception in thread" on focus changes.

No need for complex setup, basic app with osr causes this.

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