VuforiaBehaviour.Instance.enabled = false does not pause Vuforia

[StefanLewin]

Summarize the bug:
Before, we used VuforiaBehaviour.Instance.enabled = false to pause the Vuforia Engine, so the currently detected target won't get lost. This does not seem to work anymore.

Observed problem
I tested this behaviour, by using the VuforiaApplication.Instance.OnVuforiaPaused and VuforiaApplication.Instance.OnVuforiaStopped events. When executing VuforiaBehaviour.Instance.enabled = false the VuforiaApplication.Instance.OnVuforiaStopped is triggered.

Expected result
I expect the VuforiaApplication.Instance.OnVuforiaPaused event to be triggered, when VuforiaBehaviour.Instance.enabled = false is executed. This behaviour is implied in the documentation

Other observations
This behaviour started after upgrading from Vuforia 10.20.3 to 11.4.4.

Reproducible steps
I tested, using this code snippet:

        private void OnEnable()
        {
            VuforiaApplication.Instance.OnVuforiaPaused += TestOutputPauseLog;
            VuforiaApplication.Instance.OnVuforiaStopped += TestOutputStoppedLog;
        }

        private void OnDisable()
        {
            VuforiaApplication.Instance.OnVuforiaPaused -= TestOutputPauseLog;
            VuforiaApplication.Instance.OnVuforiaStopped -= TestOutputStoppedLog;
        }

        private void TestOutputStoppedLog()
        {
            Debug.Log("vuforia STOP");
        }

        private void TestOutputPauseLog(bool obj)
        {
            Debug.Log("vuforia PAUSED");
        }

Affected Vuforia Engine version:
v11.4.4

Affected platform:

• Workstation OS: macOS Tahoe 26.5.1
• Platform: Unity
• Platform version: 6000.3.18f1

Affected device:
Appears in Unity Editor.

Workaround
Methods, which are supposed to exeute on VuforiaApplication.Instance.OnVuforiaStopped, are now executed, even though Vuforia is supposed to be paused. To prevent their execution, we added the following check, as a temporary workaround:

if (!VuforiaBehaviour.Instance.enabled) 
  return;

[ptc-pmessenger]

Hi @StefanLewin,
the way the lifecycle works is that OnVuforiaPaused is called when Vuforia is running, but the application gets the OnApplicationPause event from Unity. This happens typically when the app on a phone is put into the background (see unity docs for this).
Disabling Vuforia via the VuforiaBehaviour.enabled flag is an explicit stop of Vuforia.
In that sense it's working as designed.

Would you mind explaining more what exactly you're trying to achieve? Even if you were trying to pause Vuforia, that would not help with avoiding tracking loss, it would do the opposite in fact. If Vuforia is paused or stopped, tracking will stop.

[StefanLewin]

Hi, and thank you for your answer!
Your description of the lifecycle sounds plausible, but it is not, what is described in your documentation. As mentioned in my report above, the documentation states:

Pause Vuforia Engine and the tracking activities by setting VuforiaBehaviour to disabled and resume to your AR tracking experience by setting it to enabled. OnVuforiaDeinitialized should not be used as this will destroy stored resources including registered targets.

This does not indicate, that the OnVuforiaPaused event is related to the OnApplicationPause event.

What we achieved preiously with this: The user scans an image target and is then able to change the scene, using a screen space button. The new scene adapts, based on the currently scanned image target. So we display a confirmation box and VuforiaBehaviour.Instance.enabled = false allowed us to

1. Freeze the camera feed.
2. Transfer the information for the new scene, based on the currently active target.

This way, the user could decide, if they want to move to another scene, without having to keep the target in place. Also we could access the information behind the displayed model directly, because the OnTargetLost event would not fire.