Unnecessary X11 display requirement on command-line use of ACE

[angwe]

There seems to be some underlying library related to the electron module requiring a X server to display on, even though no GUI is being used.

We have a use-case to run 'ace' in a background process for users of our website (as we do with 'epubcheck'), so we would like it to run on the command line on its own.

However:

LocalMachine:~ localuser$ ssh user@server
Last login: Tue Oct 21 12:02:29 2025 from IP
[user@server ~]$ ace --version
[16465:1021/132316.372714:ERROR:ozone_platform_x11.cc(246)] Missing X server or $DISPLAY
[16465:1021/132316.372850:ERROR:env.cc(257)] The platform failed to initialize.  Exiting.
/PATH/TO/node_modules/@daisy/ace/node_modules/electron/dist/electron exited with signal SIGSEGV
[user@server ~]$ exit
logout
Connection to server closed.
LocalMachine:~ localuser$ ssh -X user@server
Last login: Tue Oct 21 13:23:02 2025 from IP
[user@server ~]$ ace --version
1.3.7
[user@server~]$

Is the assumption that anyone trying to run a command-line should use the HTTP server / API version instead?

This is on RHEL 9.6, Node 22.19.0, ACE 1.3.7.

[danielweck]

Hello, Ace uses Electron to create hidden BrowserWindows (i.e. Chromium webviews) to execute the Deque Axe runtime that evaluates the accessibility of rendered HTML documents. Historically Ace was using Puppeteer which was a true headless runtime, whereas Electron isn't. Electron is the default "runner" for Ace in order to align with the DAISY Ace App (GUI). The legacy Puppeteer "runner" remains available under the ace-puppeteer executable (while ace is effectively ace-electron. See how xvfb is used in this sample Docker config

ace/Dockerfile

Line 143 in 1579e9b

xvfb-run ./node_modules/.bin/ace-electron --no-sandbox --disable-gpu -V -f -o /ACE -t /ACE --subdir book.epub &&\

[angwe]

You probably need to update your documentation to indicate that the only truly command-line-only version of ace to run under Linux (without X11) is the ace-puppeteer command.

Although this now brings up the unfortunate possibility that the puppeteer runner won't keep up with the default electron runner. Is the project maintaining parity between the two?