Highlight warning lines in Script editor

[sockeye-d]

Adds a yellow highlight (customizable through the theme editor) to the script editor

Resolves godotengine/godot-proposals#11706

[arkology]

I think it may be good (but not necessary) to have transparency check to skip code if alpha is zero.

[sockeye-d]

I think it should have transparency check to skip code if alpha is zero.

If the alpha is set to zero, warnings are added, then changed in the editor settings to something visible, it won't change until the next time warnings are updated. This is because it won't make the lines a color other than Color(0.0, 0.0, 0.0, 0.0) and so when it updates the line colors it won't find any that match. Also since errors don't do it and it's probably a negligible performance hit I don't think it's worth it

[arkology]

I understand you point.
But at the same time:

Also since errors don't do it

Because users have errors if something is going wrong and usualy errors should be fixed. But there could by many warnings and they could be freely ignored.

This is just a suggestion (I'll rephrase previous comment) and not critical at the first glance.

[KoBeWi]

Checking for alpha would allow skipping double for loop. If setting the background color would have no effect, no reason to run this loop. Same could be done for errors.
Unless I'm misunderstanding something.

[sockeye-d]

Done for warnings and errors both, I also added the missing documentation that was causing the Linux mono build to fail I think

[Calinou]

Tested locally, it works as expected.

However, I think the default warning mark is too prominent by default and draws attention away from errors.

Default	Black (OLED)	Light

With opacity reduced by half on the warning mark color:

Default	Black (OLED)	Light

We should remember that many projects out there have dozens of warnings (if not hundreds) that were never noticed by users (and therefore not fixed), so we should ensure we don't highlight warnings too prominentl by default.

[Calinou]

Looks good to me, please squash the commits together. See PR workflow for instructions 🙂

[sockeye-d]

Commits are now squashed together