Assistance with solution for ERR_UNKNOWN_URL_SCHEME ?

[bliqqo]

Hello!

I've encountered one issue regarding the use of Zoom's website (Video Conferencing) on this package. Upon create or joining meetings (zoom us -> login -> main page -> Join / Host ), Zoom redirects leads to an ERR_UNKNOWN_URL_SCHEME, not something I've seen when using Zoom before.

I've observed successful webcam support through this package as well as successful meetings on Zoom by altering the URL- to direct the browser specifically to the web meetings. ( Referenced here: https://magpcss.org/ceforum/viewtopic.php?f=6&t=19216 )

I would like to know if there is any direction someone might have to prevent this error. Might it be resolved with a newer version update to CEF? CEFsharp? CEFGlue?

[Voltstro]

It's because of the custom URL scheme (zoommtg://). Apps can register custom URL schemes with the OS to tell browsers then when a URL with that scheme is accessed, to open the app itself. By default, CEF blocks all of these calls (for security reasons).

You can tell CEF to allow an unknown URL scheme to attempt execution via the registered OS protocol handler. This is done via the CefResourceRequestHandler.OnProtocolExecution, so you will need to override the handler in UWB's CEF engine (as it's not currently used), and check for allowed URL schemes, then set allowOSExecution to true.

[Voltstro]

You haven't setup your dev environment correctly. Your missing the cef bins which are downloaded in the setup process. Make sure you follow the dev guide correctly, and the scripts don't error. If you truly believe your environment is correct, run the download-cef-windows.ps1 script, and when you build, make sure libcef.dll is located next to the engine's exe.

You should be using the UnityProject provided in the repo like stated in the docs for development/testing, not adding the dev package to an external project and developing/testing there.

[bliqqo]

You were correct, My dev environment was not set up correctly. Upon having rebuilt and reedited my work with the correct environment multiple times, it seems to throw errors after being built (wrong procedure order possibly), or ignore my changes ( as though they weren't included in the build).

Attempt order 1:

1. clone git hub project
2. change scripts with previously discussed changes
3. run setup-all.ps1 - ( attempt run from Unity => failed run w/ errors below)
4. manual visual studios rebuild of uwb.engine.cef - ( attempt to run from Unity => failed run w/ errors below)

[Web Browser]: Error in data loop! System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.

[Web Browser]: Error in data loop! System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.
UnityEngine.Logger:LogError (string,object)

VoltstroStudios.UnityWebBrowser.Logging.DefaultUnityWebBrowserLogger:Error (object) (at D:/CleanTestSlate.2/UnityWebBrowser/src/Packages/UnityWebBrowser/Runtime/Logging/DefaultUnityWebBrowserLogger.cs:36)

VoltstroStudios.UnityWebBrowser.Core.WebBrowserClient:PixelDataLoop () (at D:/CleanTestSlate.2/UnityWebBrowser/src/Packages/UnityWebBrowser/Runtime/Core/WebBrowserClient.cs:514)

System.Threading.ThreadHelper:ThreadStart ()

[Web Browser]: It appears that the engine process has quit!

[Web Browser]: It appears that the engine process has quit!
UnityEngine.Logger:LogError (string,object)

VoltstroStudios.UnityWebBrowser.Logging.DefaultUnityWebBrowserLogger:Error (object) (at D:/CleanTestSlate.2/UnityWebBrowser/src/Packages/UnityWebBrowser/Runtime/Logging/DefaultUnityWebBrowserLogger.cs:36)

VoltstroStudios.UnityWebBrowser.Core.WebBrowserClient:PixelDataLoop () (at D:/CleanTestSlate.2/UnityWebBrowser/src/Packages/UnityWebBrowser/Runtime/Core/WebBrowserClient.cs:481)

System.Threading.ThreadHelper:ThreadStart ()

Attempt order 2:

1. clone git hub project
2. run setup-all.ps1
3. change scripts with previously discussed changes - ( attempt to run from Unity => success with no sign of my changes)
4. manual visual studios rebuild of uwb.engine.cef - ( attempt to run from Unity => success with no sign of my changes)

Is there a certain order to set up the project with these changes?

I'll keep saying it so long as your still here, really appreciate the continued assistance

[Voltstro]

The order to setup everything is:

1. Clone the repo recursively
2. Run setup-all.ps1 script with PowerShell
   • Check for errors, make sure there are none
3. Open src/UnityWebBrowser.UnityProject with Unity, open the scene, and run it to check that the default build works
4. Do your changes
5. Run the dev script for the project(s) that you are modifying (E.G: publish-cef-engine-windows.ps1)
6. Test in the Unity project again

The new errors you have provided indicate that the CEF engine process is crashing. You can build the external projects in your IDE of choice with the configuration set to debug for a no-strip, symbols build. Then run the engine process that is built to <Project>/bin/Debug with the command line to see the errors. (Note, you may be able to run the project through your IDE to attach a debugger and do your debugging like that, but I know that atleast on a Linux dev environment with JetBrain's Rider the engine process will always crash when a debugger is attached)

You can launch the process with the arguments -remote-debugging 5555 to use Chromium's remote headless debugger (on a normal browser goto localhost:5555 to access it). There is also -log-severity Debug for debug logging level.

[bliqqo]

Thanks to all your advice, I have found a solution for the time being. (maybe not the solution, but one that works for me)

The new errors you have provided indicate that the CEF engine process is crashing. You can build the external projects in your IDE of choice with the configuration set to debug for a no-strip, symbols build. Then run the engine process that is built to /bin/Debug with the command line to see the errors. (Note, you may be able to run the project through your IDE to attach a debugger and do your debugging like that, but I know that atleast on a Linux dev environment with JetBrain's Rider the engine process will always crash when a debugger is attached)

This lead me to finding my own exceptions/bugs in my handler, that I wasn't handling correctly. Fixing that and the correctly ordering my setup (as you detailed) created a stable environment for me to make the custom changes to UWB's CEF.

Using UwbCefLoadHandler & UwbCefClient I intercept the URL that will throw the error and replace it with a functional URL (without the odd scheme). This might work in zoom's case, I don't know how useful this might be in other situations, although.

My handler is operating but was not solving the ERR_UNKNOWN_URL_SCHEME, despite overriding the allowOSExection. Which is why I tried the URL interception.

You can tell CEF to allow an unknown URL scheme to attempt execution via the registered OS protocol handler. This is done via the CefResourceRequestHandler.OnProtocolExecution, so you will need to override the handler in UWB's CEF engine (as it's not currently used), and check for allowed URL schemes, then set allowOSExecution to true.

Do you need to manually state the allowed URL scheme's anywhere, or was that purely a suggestion before setting allowOSExecution to be true?

Could not have gotten this far without your assistance, thank you.

[Voltstro]

Using UwbCefLoadHandler & UwbCefClient I intercept the URL that will throw the error and replace it with a functional URL (without the odd scheme). This might work in zoom's case, I don't know how useful this might be in other situations, although.

If your goal is just to purely open Zoom inside of UWB, rather than allow the desktop app, then yea, using URL redirection should be fine.

Do you need to manually state the allowed URL scheme's anywhere, or was that purely a suggestion before setting allowOSExecution to be true?

I don't think so? I mainly suggested checking the scheme due to the security warning stated in the CEF docs.