Scene3DTest/Events Flaky on Github Actions CI

[Blast545]

Environment

• OS Version: Ubuntu Bionic/Focal on Github Actions
• Source, Citadel confirmed

Description

• Expected behavior: Test should pass.
• Actual behavior: Test segfaults sometimes.

Steps to reproduce

1. Open a PR targeting gz-gui3
2. Re-run Ubuntu CI workflow for a couple of times.

Output

On Bionic:

 [ RUN      ] Scene3DTest.Config
  [GUI] [Dbg] [Application.cc:92] Initializing application.
  [GUI] [Dbg] [Application.cc:543] Create main window
  [GUI] [Dbg] [Application.cc:420] Loading plugin [Scene3D]
  [GUI] [Msg] Added plugin [3D Scene] to main window
  [GUI] [Msg] Loaded plugin [Scene3D] from path [/github/workspace/build/lib/libScene3D.so]
  [GUI] [Msg] Loading plugin [ignition-rendering-ogre]
  [GUI] [Msg] Loading plugin [ignition-rendering-ogre]
  [GUI] [Dbg] [Scene3D.cc:1099] Create scene [banana]
  [GUI] [Dbg] [Application.cc:140] Terminating application.
  [GUI] [Msg] Loading plugin [ignition-rendering-ogre]
  [GUI] [Dbg] [Scene3D.cc:1155] Destroy scene [banana]
  [       OK ] Scene3DTest.Config (994 ms)
  [ RUN      ] Scene3DTest.Events

On Focal:

[ RUN      ] Scene3DTest.Config
  [GUI] [Wrn] [Application.cc:785] [QT] QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
  [GUI] [Dbg] [Application.cc:92] Initializing application.
  [GUI] [Dbg] [Application.cc:543] Create main window
  [GUI] [Dbg] [Application.cc:420] Loading plugin [Scene3D]
  [GUI] [Msg] Added plugin [3D Scene] to main window
  [GUI] [Msg] Loaded plugin [Scene3D] from path [/github/workspace/build/lib/libScene3D.so]
  [GUI] [Msg] Loading plugin [ignition-rendering-ogre]
  [GUI] [Msg] Loading plugin [ignition-rendering-ogre]
  [GUI] [Dbg] [Scene3D.cc:1099] Create scene [banana]
  [GUI] [Dbg] [Application.cc:140] Terminating application.
  [GUI] [Msg] Loading plugin [ignition-rendering-ogre]
  [GUI] [Dbg] [Scene3D.cc:1155] Destroy scene [banana]
  [       OK ] Scene3DTest.Config (659 ms)
  [ RUN      ] Scene3DTest.Events
  [GUI] [Wrn] [Application.cc:785] [QT] QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
  [GUI] [Dbg] [Application.cc:92] Initializing application.
  [GUI] [Dbg] [Application.cc:543] Create main window
  [GUI] [Dbg] [Application.cc:420] Loading plugin [Scene3D]
  [GUI] [Msg] Added plugin [3D Scene] to main window
  [GUI] [Msg] Loaded plugin [Scene3D] from path [/github/workspace/build/lib/libScene3D.so]
  [GUI] [Msg] Loading plugin [ignition-rendering-ogre]
  [GUI] [Dbg] [Scene3D.cc:1099] Create scene [banana]
  /github/workspace/test/integration/scene3d.cc:222: Failure
  Value of: receivedRightEvent
    Actual: false
  Expected: true
  /github/workspace/test/integration/scene3d.cc:225: Failure
  Expected equality of these values:
    leftClickPoint
      Which is: 0.999643 11.977 3.81304
    rightClickPoint
      Which is: 0 0 0
  [GUI] [Dbg] [Application.cc:140] Terminating application.
  [GUI] [Msg] Loading plugin [ignition-rendering-ogre]
  [GUI] [Dbg] [Scene3D.cc:1155] Destroy scene [banana]
  [  FAILED  ] Scene3DTest.Events (12308 ms)

It segfaults without generating any kind of information.

Reference, see:
Bionic: https://github.com/gazebosim/gz-gui/runs/6922533094?check_suite_focus=true
Focal: https://github.com/gazebosim/gz-gui/runs/6912020143?check_suite_focus=true

This may be fixed by setting the proper value to XDG_RUNTIME_DIR. Taking a closer look later.