feat(tui-scrollview): add scrollbars visibility handling

[ulissesf]

Add ScrollbarVisibility enum with Automatic (default), Always, and Never variants. Also add fluent setter methods horizontal_scrollbar_visibility(), vertical_scrollbar_visibility() and scrollbars_visibility() to ScrollView.

let mut sv_no_vert = ScrollView::new(Size::new(20, 20))
    .vertical_scrollbar_visibility(ScrollbarVisibility::Never);

let mut sv_allways_bars = ScrollView::new(Size::new(50, 80))
    .scrollbars_visibility(ScrollbarVisibility::Always);

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 73 lines in your changes missing coverage. Please review.

Project coverage is 0.00%. Comparing base (e65caad) to head (e425956).

Files with missing lines	Patch %	Lines
tui-scrollview/src/scroll_view.rs	0.00%	73 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main     #45   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files          2       2           
  Lines        150     190   +40     
=====================================
- Misses       150     190   +40     

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[ulissesf]

@joshka Tell which part of the format checks you'd want solved. It's complaining about the tests too, but I followed the format already there in the other ones.

As for the scrollbars rendering, I kept returning the remaining area from render_scrollbars() as it does take up space and it still seemed a good approach. The code still assumes we have vertical scrollbar on the right and horizontal at the bottom (as it was before). I could add setters for that in a follow-up PR and then likely rendering_scrollbars() will need to return more information or maybe already the visible area from the scrollview's buffer and where to render it.

[joshka]

I tweaked this for a bunch of nitpicks that are fairly opinionated preferences rather than problems with the code. It would have been annoying to communicate these, so easier to just do them:

• function ordering (caller then callee)
• changed SBV to just V
• changes the naming a bit
• removed the Info struct and put the vars in the main struct.
• use less abbreviations
• changed _fit to _space as it made more sense what this was describing
• simplified the big else-if block

[joshka]

Thanks for the PR on this. I'll release it in a bit.

[ulissesf]

I tweaked this for a bunch of nitpicks that are fairly opinionated preferences rather than problems with the code. It would have been annoying to communicate these, so easier to just do them:

• function ordering (caller then callee)
• changed SBV to just V
• changes the naming a bit
• removed the Info struct and put the vars in the main struct.
• use less abbreviations
• changed _fit to _space as it made more sense what this was describing
• simplified the big else-if block

Thanks. Yes, it'd indeed take some more time than just doing it. You making the changes still helps me learn how you like things in case I send another PR, I appreciate it.