brew installed octave contains no graphics toolkit, preventing github action headless plots

[fangq]

Additional Info

• I am using Windows Subsystem for Linux

Output of brew config

N/A

Output of brew doctor

N/A

Description of issue

The issue has been reported in Homebrew/brew#18595, github action testing an octave toolbox failed on both macos-13 and macos-14 runners

https://github.com/fangq/iso2mesh/actions/runs/11413968520/job/31762253381
https://github.com/fangq/iso2mesh/actions/runs/11408582821/job/31747587033

the error is

error: no graphics toolkits are available!

in comparison, other Linux/windows runners all present a default graphics_toolkit,allow CI script containing plots in headless mode. However, it appears that the macos-13 and -14 versions of octave were built differently in brew.

as suggested by @Bo98 in Homebrew/brew#18595, because macos-12 runner brew install octave, especially brew install qt took forever to complete due to the stop of support, I would like to migrate my github action to macos-13 and -14, but need your help in resolving the graphics toolkit error above.

is there a way to enable graphics toolkit in brew compiled octave in order to use in github action tests?

[cho-m]

I think it should be able to use fltk but doesn't seem to be found, e.g.

❯ octave-cli --eval 'available_graphics_toolkits()'
ans = {}(1x0)

Most functional option is just standard Qt octave which may still work in CI given we do sometimes run tests on GitHub runner.

❯ octave --eval 'available_graphics_toolkits()'
ans =
{
  [1,1] = qt
}

It looks like your Ubuntu test runs via gnuplot.

On macOS, Octave can use gnuplot though output won't actually work unless unmaintained AquaTerm.app (aquaterm cask) is installed so not ideal. You can see if installing just gnuplot gets you past the error

❯ brew install gnuplot
❯ octave-cli --eval 'available_graphics_toolkits()'
ans =
{
  [1,1] = gnuplot
}

[fangq]

@cho-m, thank you so much! brew install gnuplot solved the problem.

I am wondering why gnuplot is not setup as a dependency for octave? without a fall-back graphics toolkit, octave-cli won't be able to run any script with plotting functions, which is quite limiting.

[gromgit]

I am wondering why gnuplot is not setup as a dependency for octave?

Perhaps because no one felt the need to use it with octave, or because they already had gnuplot installed for some other reason, so everything Just Worked?

If you feel gnuplot should be a required dependency, you can file a PR: https://docs.brew.sh/How-To-Open-a-Homebrew-Pull-Request