Add button_url[] and hypertext element to allow mods to open web pages

[rubenwardy]

Fixes #12500

This adds a new type of button and a hypertext attribute to allow opening URLs in a web browser. A button is used to require user interaction before opening URLs.

A confirmation dialog is shown, to allow the user to see the URL. Unfortunately, this confirmation dialog has to be implemented using raw Irrlicht GUI for security reasons, so cannot be themed by games and looks a bit odd compared to the rest of the GUI. This should be improved in the future

To do

This PR is Ready for Review

• Clean up parseButtonURL duplication
• Fix line wrapping / scrolling to see entire URL in box
• Highlight domain name
• Add hypertext tag (maybe for a next PR?)
• Fix CURLU_PUNYCODE requiring Curl 7.88
• Improve dialog message (suggestions welcome)

For future PRs:

• Add ability to 'trust' domain names

How to test

Click the red button in the Styled tab of /test_formspec in devtest

Click the URL link in the hypertext tab

[Desour]

It would be nice if the editbox was editable, so that user can remove parts of the url before opening it.

[oong819]

Δяε tΗeгe aпythΙng тo ρяevеnτ homοgrаph？

еχаmрle.org

[rubenwardy]

Not yet. I'd like to use a font that distinguishes a lot of things differently (ie I vs l) and I'd also like to color letters based on character class (which would highlight homographs)

[rubenwardy]

The dialog now uses a mono font and colorizes the URL. Non alphanumeric characters are shown as red, for example the Cyrillic small letter a here:

[rubenwardy]

One option would be to show the punycode instead:

If the URL doesn't contain unsafe characters, it appears as normal:

[appgurueu]

I support showing punycode, especially as I don't trust our Unicode handling enough to make sure that Unicode characters would be properly discernible.

I would also be fine with only allowing ASCII for a first implementation. URLs are largely ASCII-encodable, and if not, you can still have an ASCII-only URL redirect to the target URL.

[rubenwardy]

Done. Also added break word line wrapping (need to fix follow on line colors)

[rubenwardy]

You can now open links from hypertext:

<action name=open url=https://example.com/?a=b#c>open URL</action>

[sfan5]

code complaints only :)

[rubenwardy]

[sfan5]

works