fix(SDKManager): SDK Setup load/unload crashes on scene changes

Whenever the scene changed it was recommended to unload the
currently loaded SDK Setup via the SDK Manager. This lead to issues
with coming up with the exact time to call the unload method,
especially when using `SteamVR_LoadLevel`. That SteamVR script even
lead to crashes.

This fix stops unloading the currently used VR Device everywhere.
The result is that **there is no need to call the unload method
manually anymore**.

The SceneChanger script was simplified a bit after being updated for
this fix.

Author: Christopher-Marcel Böddecker

Assets/VRTK/Examples/ExampleResources/Scripts/SceneChanger.cs

@@ -15,7 +15,7 @@ private void Awake()
             DynamicGI.UpdateEnvironment();
         }
 
-        private bool ForwardPressed()
+        private bool IsForwardPressed()
         {
             if (!VRTK_ControllerReference.IsValid(controllerReference))
             {
@@ -31,7 +31,7 @@ private bool ForwardPressed()
             return false;
         }
 
-        private bool BackPressed()
+        private bool IsBackPressed()
         {
             if (!VRTK_ControllerReference.IsValid(controllerReference))
             {
@@ -57,27 +57,29 @@ private void Update()
         {
             GameObject rightHand = VRTK_DeviceFinder.GetControllerRightHand(true);
             controllerReference = VRTK_ControllerReference.GetControllerReference(rightHand);
-            if (ForwardPressed() || Input.GetKeyUp(KeyCode.Space))
+
+            int currentSceneIndex = SceneManager.GetActiveScene().buildIndex;
+            int nextSceneIndex = currentSceneIndex;
+
+            if (IsForwardPressed() || Input.GetKeyUp(KeyCode.Space))
             {
-                int nextSceneIndex = SceneManager.GetActiveScene().buildIndex + 1;
+                nextSceneIndex++;
                 if (nextSceneIndex >= SceneManager.sceneCountInBuildSettings)
-                {
                     nextSceneIndex = 0;
-                }
-                VRTK_SDKManager.instance.UnloadSDKSetup();
-                SceneManager.LoadScene(nextSceneIndex);
+            }
+            else if (IsBackPressed() || Input.GetKeyUp(KeyCode.Backspace))
+            {
+                nextSceneIndex--;
+                if (nextSceneIndex < 0)
+                    nextSceneIndex = SceneManager.sceneCountInBuildSettings - 1;
             }
 
-            if (BackPressed() || Input.GetKeyUp(KeyCode.Backspace))
+            if (nextSceneIndex == currentSceneIndex)
             {
-                int previousSceneIndex = SceneManager.GetActiveScene().buildIndex - 1;
-                if (previousSceneIndex < 0)
-                {
-                    previousSceneIndex = SceneManager.sceneCountInBuildSettings - 1;
-                }
-                VRTK_SDKManager.instance.UnloadSDKSetup();
-                SceneManager.LoadScene(previousSceneIndex);
+                return;
             }
+
+            SceneManager.LoadScene(nextSceneIndex);
         }
     }
 }

Assets/VRTK/Scripts/Utilities/SDK/VRTK_SDKManager.cs

@@ -384,6 +384,43 @@ public void RemoveBehaviourToToggleOnLoadedSetupChange(Behaviour behaviour)
             _behavioursToToggleOnLoadedSetupChange.Remove(behaviour);
         }
 
+        /// <summary>
+        /// Tries to load a valid <see cref="VRTK_SDKSetup"/> from <see cref="setups"/>.
+        /// </summary>
+        public void TryLoadSDKSetupFromList()
+        {
+            int index = 0;
+
+            if (VRSettings.enabled)
+            {
+                // Use the SDK Setup for the current VR Device if it's working already
+                // (may be due to command line argument '-vrmode')
+                index = Array.FindIndex(
+                    setups,
+                    setup => setup.usedVRDeviceNames.Contains(VRSettings.loadedDeviceName)
+                );
+            }
+            else
+            {
+                // If '-vrmode none' was used try to load the respective SDK Setup
+                string[] commandLineArgs = Environment.GetCommandLineArgs();
+                int commandLineArgIndex = Array.IndexOf(commandLineArgs, "-vrmode", 1);
+                if (VRSettings.loadedDeviceName == "None"
+                    || (commandLineArgIndex != -1
+                        && commandLineArgIndex + 1 < commandLineArgs.Length
+                        && commandLineArgs[commandLineArgIndex + 1].ToLowerInvariant() == "none"))
+                {
+                    index = Array.FindIndex(
+                        setups,
+                        setup => setup.usedVRDeviceNames.All(vrDeviceName => vrDeviceName == "None")
+                    );
+                }
+            }
+
+            index = index == -1 ? 0 : index;
+            TryLoadSDKSetup(index, false, setups.ToArray());
+        }
+
         /// <summary>
         /// Tries to load a valid <see cref="VRTK_SDKSetup"/> from a list.
         /// </summary>
@@ -492,7 +529,7 @@ public void SetLoadedSDKSetupToPopulateObjectReferences(VRTK_SDKSetup setup)
         /// Unloads the currently loaded <see cref="VRTK_SDKSetup"/>, if there is one.
         /// </summary>
         /// <param name="disableVR">Whether to disable VR altogether after unloading the SDK Setup.</param>
-        public void UnloadSDKSetup(bool disableVR = true)
+        public void UnloadSDKSetup(bool disableVR = false)
         {
             if (loadedSetup != null)
             {
@@ -538,43 +575,15 @@ private void OnEnable()
 
             if (autoLoadSetup)
             {
-                int index = 0;
-
-                if (VRSettings.enabled)
-                {
-                    // Use the SDK Setup for the current VR Device if it's working already
-                    // (may be due to command line argument '-vrmode')
-                    index = Array.FindIndex(
-                        setups,
-                        setup => setup.usedVRDeviceNames.Contains(VRSettings.loadedDeviceName)
-                    );
-                }
-                else
-                {
-                    // If '-vrmode none' was used try to load the respective SDK Setup
-                    string[] commandLineArgs = Environment.GetCommandLineArgs();
-                    int commandLineArgIndex = Array.IndexOf(commandLineArgs, "-vrmode", 1);
-                    if (commandLineArgIndex != -1
-                        && commandLineArgIndex + 1 < commandLineArgs.Length
-                        && commandLineArgs[commandLineArgIndex + 1].ToLowerInvariant() == "none")
-                    {
-                        index = Array.FindIndex(
-                            setups,
-                            setup => setup.usedVRDeviceNames.All(vrDeviceName => vrDeviceName == "None")
-                        );
-                    }
-                }
-
-                index = index == -1 ? 0 : index;
-                TryLoadSDKSetup(index, false, setups.ToArray());
+                TryLoadSDKSetupFromList();
             }
         }
 
         private void OnDisable()
         {
-            if (_instance == this && !persistOnLoad)
-            {
-                UnloadSDKSetup();
+            if (_instance == this && !persistOnLoad)
+            {
+                UnloadSDKSetup();
             }
         }
 

Assets/VRTK/Scripts/Utilities/SDK/VRTK_SDKSetupSwitcher.cs

@@ -133,7 +133,7 @@ protected virtual void AddSelectionButtons()
                 chooseNoneButton.SetActive(true);
 
                 chooseNoneButton.GetComponent<Button>().onClick.AddListener(
-                    () => sdkManager.UnloadSDKSetup()
+                    () => sdkManager.UnloadSDKSetup(true)
                 );
 
                 chooseButtonGameObjects.Add(chooseNoneButton);