Introducing wpe-webkit-mir-kiosk snap

tcfx44 · December 12, 2019, 5:11pm

Still the same. I read somewhere that the WAYLAND_DIPLSAY environment variable may not be set and causing this problem.

alan_g · December 12, 2019, 5:44pm

Setting WAYLAND_DISPLAY could cause an issue. Not setting it shouldn’t.

I can’t guess why you would have a problem specific to Server. Sorry.

lookitscook · December 19, 2019, 4:26am

@tobias just tried out this snap on rpi 3b+ and worked great. nice work! I’m working on porting an existing kiosk chrome app to native snap functionality to start targeting Ubunutu (instead of Chrome OS) as my primary recommended platform.

I’d love to use fork your snap as a starting point. Would you consider MIT (or compatible) license for it?

Edit: I attempted to create a merge request to kick things off, but I’m not seeing the option on gitlab. Is reduced visibility turned on for that repo?

tobias · January 10, 2020, 1:57pm

@lookitscook sorry for the long delay, the notification got buried in my emails and I was busy with non-snapcraft work for a while

Yes, we’re considering MIT(-compatible) licensing. The only thing I’d ask of you is to contribute back changes which you deem fit for general use. You can have a look at the current issues, for which contributions are especially welcome!

I have enabled merge requests for the repository, so please do open one!

markus · January 30, 2020, 8:40am

Nice and useful snap. How can I troubleshoot why my display (RPI 3b+) goes black after about 24 hours?

tobias · January 30, 2020, 9:14am

Thanks!

For debugging, please check the snap service’s log by running sudo snap logs wpe-webkit-mir-kiosk.browser.

If there are a lot of messages, you may need to retrieve more lines with sudo snap logs -n<number of lines> wpe-webkit-mir-kiosk.browser, try -n200 for a start.

Also, check if mir-kiosk has gotten an update (snap info mir-kiosk → last refresh date). mir-kiosk has to reboot during a snap refresh, which obviously kills the Wayland compositor for WPE. My snap’s service is configured to restart on fatal errors, but WPE doesn’t seem to throw a fatal error if the Wayland context goes away. Without such a signal from the process, the snap service doesn’t restart automatically.

Next stop would be to check if there are fatal JavaScript errors on your page that crash the render thread. You’ll need to snap set either

devmode=true to access the browser console via Remote Inspector (inspector://<your-rpi-ip-address-or-hostname>:8080 from any WebKit GTK+ browser (see docs)
error-to-console to log JS errors to the service log, accessible via the snap logs command from above.
In both cases, the browser has to restart, which will wipe JS error logs, so you’ll need to wait until the error reoccurs.

Hope that helps!

markus · January 30, 2020, 9:52am

Thanks for the quick and elaborate response.

All snap restarts due to settings changes did not bring back the browser screen. The log shows no suspicious entries. Regrettably, I cannot use Remote Inspector since my current workhorse uses Windows (I will try to get something else) and it seems there are no Webkit-based browsers for Windows. The only console error appearing after enabling local logging are “wpe-webkit-mir-kiosk.browser[8114]: realpath: ‘’: No such file or directory”:

I don’t know if I can rule out failing hardware since I cannot switch to another console (the screen stays black but the backlight seems to stay on). I’ll try to get additional devices running and to observe the error.

alan_g · January 30, 2020, 10:24am

@markus a quick way to get more information on where the failure is would be to restart mir-kiosk:

snap restart mir-kiosk

As mir-kiosk restarts you should see an orange “flash” on the screen.

If you don’t see that, then the problem is not wpe-webkit - either the hardware or mir-kiosk is failing.
If you do see that, you know the hardware is working and that mir-kiosk starts.

tobias · January 30, 2020, 10:32am

The realpath: No such file … error also occurs on regular launches; started to occur somewhere after a WPE version bump. Didn’t have the time to investigate yet, but it does not seem to cause any error.

Which version of the snap are you currently using (architecture + revision)? Also, there’s a bug with mount namespaces which is fixed as of 2.42.3, but was initially behind a feature flag. Quickly scanning release notes, I don’t know whether 2.43 enabled the fix by default.

And what @alan_g says

markus · January 30, 2020, 10:34am

@alan_g, thanks for the hint. I’ll try that the next time the screen goes black. When I rebooted the device the console with the cursor showed before the actual reboot. I think this rules out a hardware issue.

markus · January 30, 2020, 10:36am

__@localhost:~$ snap info mir-kiosk
name:      mir-kiosk
summary:   A minimal Mir based shell for kiosk type applications
publisher: Canonical✓
license:   GPL-3.0 OR GPL-2.0
description: |
  A minimal Mir based shell for kiosk type applications
commands:
  - mir-kiosk
services:
  mir-kiosk.daemon: simple, enabled, active
snap-id:      rW4inp7UbJb1YBxWr6SVebxa3Yv7K1Vm
tracking:     stable
refresh-date: 3 days ago, at 13:52 CET
channels:
  stable:    1.7.0-snap93        2020-01-17 (3057) 28MB -
  candidate: 1.7.0-snap93        2020-01-21 (3113) 28MB -
  beta:      ↑
  edge:      1.7.0+dev312-snap93 2020-01-24 (3148) 28MB -
installed:   1.7.0-snap93                   (3057) 28MB -

__@localhost:~$ uname -a
Linux localhost 4.15.0-1054-raspi2 #58-Ubuntu SMP PREEMPT Wed Jan 15 19:28:59 UTC 2020 armv7l armv7l armv7l GNU/Linux

tobias · January 30, 2020, 10:52am

I meant the WPE revision, but I guess you’re using stable/latest

If complete service restarts (i.e. browser restarts) don’t solve the issue, a JS issue isn’t likely. Regarding hardware/mir-kiosk issues: AFAIK, the console cursor isn’t rendered by mir-kiosk, so there might be something else with GPU / modes / related (wildly guessing, out of my depth here). You may restart mir-kiosk right now as well, if the orange flash that @alan_g mentioned appears, then that part is working.

markus · January 30, 2020, 10:59am

Sorry about the confusion. I am using wpe-webkit-mir-kiosk 2.26.2 (latest, stable). It seems it is the restart (attempt) that actually results in the black screen (after the orange flash), I just tried it. I am using the original Raspberry Pi 7" touch screen. The resolution has been set to 800x400.

alan_g · January 30, 2020, 11:12am

The next thing I’d try is a different kiosk snap - e.g.

snap install --beta mir-kiosk-apps

If that also doesn’t work, then there’s something going wrong with mir-kiosk. (Unlikely, given that we’ve established it starts - but it’s worth checking.) If mir-kiosk-apps does work, then it’s down to wpe-webkit-mir-kiosk. Maybe try uninstall/reinstall?

ogra · January 30, 2020, 11:30am

seems to be this:

github.com

ubuntu/snapcraft-desktop-helpers/blob/master/common/desktop-exports#L51


      
          
              if [ "$save_initial_values" = true ]; then
                XDG_SPECIAL_DIRS+=("$var")
                XDG_SPECIAL_DIRS_INITIAL_PATHS+=("$value")
              fi
          
              XDG_SPECIAL_DIRS_PATHS+=("$value")
            done
          }
          
          function is_subpath() {
            dir=$(realpath $1)
            parent=$(realpath $2)
            [ "${dir##$parent/}" != "$dir" ] && return 0 || return 1
          }
          
          WITH_RUNTIME=no
          if [ -z "$RUNTIME" ]; then
            RUNTIME=$SNAP
          else
            # add general paths not added by snapcraft due to runtime snap

i guess the desktop helpers dont really get enough testing with core based kiosk setups.

is_subpath() seems to be used across them to determine the actual $HOME (which is indeed a bit different in user-less kiosks)

tobias · January 30, 2020, 11:50am

Sweet, thanks! What would be a good condition to test if the snap is running in such a user-less kiosk environment? I’ll open a PR for this.

markus · January 30, 2020, 11:58am

mir-kiosk-apps comes back after restarting mir-kiosk. I un-/reinstalled wpe-webkit-mir-kiosk but the behavior does not improve.

ogra · January 30, 2020, 12:03pm

make sure to use snap remove --purge ... to be sure the whole $SNAP_DATA is wiped (IIRC snap remove saves a snapshot that it might re-apply during re-install when not using --purge)

tobias · January 30, 2020, 1:20pm

Ping @ogra

markus · February 3, 2020, 7:15am

Thanks. This may have fixed it. I purged and reinstalled wpe-webkit-mir-kiosk and the display now worked for four days. It also comes back after stopping and starting the snap.