Outline focused element when tab is pressed.

[siliconsniffer]

Add compact, short information about your PR for easier understanding:

Note

I used an LLM Chatbot/Assistant during development, but I take full responsibility for the submitted changes.

• Goal of the PR
  Improve keyboard-only navigation by outlining the currently focused element.
  Future gamepad support would also benefit from this.
• How does the PR work?
  This PR adds a hard-coded white rectangle, which appears around the next focused element when tab is pressed.
• Does it resolve any reported issue?
  Addresses Show GUI element focus #16137
  Closes Allow keyboard only use of formspecs #11392
  Related Formspec buttons mega-issue #14425
• Does this relate to a goal in the roadmap?
  Not directly, maybe 2.3.
• If not a bug fix, why is this PR needed? What usecases does it solve?
  This is an industry standard: OSes like Android or Windows and many applications, e.g., Firefox, have very similar functionality. It makes it easier to figure out which element is focused.
• If you have used an LLM/AI to help with code or assets, you must disclose this.
  Disclosed.

To do

This PR is ready for review.

How to test

open luanti → press tab/shift+tab → observe that the focused element is outlined in white

Preview

2026-01-02.13-43-35.mp4

[rubenwardy]

I haven't tried this out yet. But I'd make sure the outline only appears when the keyboard or gamepad is used to focus, and not when clicking or otherwise focusing

[siliconsniffer]

That's exactly what it does: the outline appears when pressing tab with or without shift and disappears when clicking somewhere with the mouse. It does not appear when pressing ctrl and tab.

[siliconsniffer]

In my opinion #14531 can be addressed in a follow-up PR.

[appgurueu]

Currently, tables can be focused and can shift focus to the previous element but not the next. Is this behavior intended and expected by the user?

I would say no, "previous" and "next" should be symmetric.

[siliconsniffer]

I agree and fixed this in dff25c2. This should be ready for a second round of reviews then.
What about the style? I sometimes find the outline hard to spot.

[siliconsniffer]

This is how it looks with doubled thickness.

[appgurueu]

What about the style? I sometimes find the outline hard to spot.

I think ideally there should be a formspec way of styling the color and maybe the thickness, for two reasons: In a light (white) style, the outline might be barely noticeable; game developers might want the outline to fit in with the color scheme of their menus. But it's probably fine to add such an option later?

2px thickness seems ok to me, though of course it depends a bit on screen resolution.

[rubenwardy]

If we allow styling, it should still be possible for users to override to make it very obvious for accessibility reasons

Also we have a focus selector for buttons already, but no focus-visible selector or an outline style property

[SmallJoker]

The feature works as described - but unlike in other apps (e.g. webbrowser), the focussed element is not actively brought into the visible part of the frame.
Example: hold Tab in the Settings menu. I would expect it to automatically scroll down such that the focussed element can be seen.

[siliconsniffer]

autoscroll.mp4

[siliconsniffer]

autoscroll_vert.mp4

[SmallJoker]

Works