[cross-post] chromium-mir-kiosk in portrait mode (rotated mir-kiosk layout)

snapcraft
17

@alan_g I managed to get the snap running properly: on Ubuntu 18.04 LTS desktop both with miral-kiosk or mir-kiosk with edge core; on Ubuntu Core using mir-kiosk with stable core. I’ll outline the main steps below, for fellow snap crafters that may run into similar issues (or have the same lack of experience with graphic stacks as I had). So bear with me – or skip to “Questions” :slight_smile:

The main problem were missing/wrong XDG environment variables inside the snap env. After I adapted them from the mir-kiosk-apps example you linked, WPE could connect to the Wayland socket and the EGL display. Then some iterative “libxyz is missing”, and it worked on Ubuntu Desktop. I added plugs and the snapcraft-preload plugin recommended by snappy-debug, and proceeded to test the ARM build on Core.

I was confused at first why the WebKit process was stuck in a crash loop after I installed the snap on Core running on a RasPi 3B. When I removed snapcraft-preload from the startup command, it stopped crashing – but loading any trivial website had weird issues that indicated that the browser can’t find libraries despite LD_LIBRARY_PATH being set. Issues like no images, no SSL/TLS despite libglib-networking being present etc. Also, this was in devmode, where WPE Webkit may access /dev/shm (which I gathered snapcraft-preload provides a workaround for in strict mode).

The WPE WebKit backend libwpebackend-fdo relies on the FreeDesktop.org stack, so I added the gtk3-desktop helper. Now everything works fine, I added two basic configuration options (URL and a toggle for the Remote Web Inspector) as well.

Some links to WPE WebKit in general: https://wpewebkit.org → main site https://github.com/WebPlatformForEmbedded → GitHub org https://github.com/Igalia/cog → Fullscreen browser launcher used in this snap

Questions

I added TODO / FIXME to snapcraft.yaml to indicate the work-in-progress parts. Most concern dependencies for building/running WPE Webkit, but I’d be stoked if someone can answer me these questions which I think are more related to snapcraft/Core/mir:

  1. From experience with other snaps, would a slimmer desktop-helper than gtk3 suffice to provide the “normal” FDO stack required by libwpebackend-fdo? Including this helper brings the snap from ~75 to ~114MB. (Also asked this the WPE maintainers: libwayland-client and libwayland-server may suffice)
  2. The browser fails to resolve zeroconf/Bonjour hostnames, though it works fine when building and running cog + WPE WebKit natively works fine. I included some avahi-related libs and connected the avahi-observe interface, but I guess I’m missing something fundamental here.

Meta

I’d like to suggest amending the docs for Debugging building snaps with a workflow that sped up my debugging on-device (ARM snap on a RasPi 3) tremendously:

  1. Let the ARM build run on Launchpad – takes ~ 3h for the WPE snap instead of forever (or probably failing due to limited CPU/RAM) when building on a RasPi
  2. Load the snap file from LP to your device, either via scp from your main machine or using @ondra 's great toolbox snap
  3. Run unsquashfs -d my-dir-name the-snap-file_0.1.0_somearch.snap
  4. You can now snap try my-dir-name (optionally with --devmode) and edit all files in my-dir-name to your heart’s content, all instantly reflected inside the snap. Only when editing my-dir-name/meta/snap.yaml to change app commands/services or add interfaces, you need to remove and re-mount the snap (via snap try).

Step 4 (snap try) is already documented there, but I think fleshing out an extra sentence how that works if you only have a .snap file (LP build or snapcraft 3 with bases) can help expediting dev workflows.

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