[cmake] allow disabling Gui

[silverweed]

This Pull request:

Adds a gui build option that allows disabling the Gui library. It is meant to be used in conjunction with minimal=on as no effort is made to make sure that the option is coherent with the set of other options, meaning turning the gui off by itself won't automatically disable all its dependent modules. However, when minimal is on, everything works fine.

Rationale

When someone builds with minimal=on they don't care about graphics (otherwise they'd use gminimal) and building the graphics libraries is a waste of time. AFAIK, the gui already doesn't work when building with minimal=on, so we can spare time by not building it.

Ideally we should be able to also disable graf2d and graf3d, however too many core packages depend on them to be as easily doable (we'd have to disable half of the math/tree/hist modules and rethink modules.idx and hsimple.root), so that'll remain a wish for the future.

Checklist:

• tested changes locally
• updated the docs (if necessary)

[vepadulano]

Just a fly-by comment

the gui already doesn't work when building with minimal=on

I can confirm this

[github-actions]

Test Results

0 tests   0 ✅  0s ⏱️
0 suites  0 💤
0 files    0 ❌

Results for commit 8534830.

♻️ This comment has been updated with latest results.

[bellenot]

Thanks Jack!

[silverweed]

@bellenot @dpiparo Following Stephan's suggestion, instead of using a new build option I'm now directly checking for NOT minimal, which has 2 benefits:

• avoids introducing a new build option
• avoids unsupported cases where one has gui=off but without minimal=on

[bellenot]

@bellenot @dpiparo Following Stephan's suggestion, instead of using a new build option I'm now directly checking for NOT minimal, which has 2 benefits:

• avoids introducing a new build option
• avoids unsupported cases where one has gui=off but without minimal=on

I fully agree!