Scrolling TabBar

[robob27]

• Modify TabBar to allow tabs to be scrolled instead of wrapping by setting wrap=false in the TabBar attributes. wrap defaults to true so any existing instances of TabBar should be unaffected (tested with launcher and control-panel and they're looking good).
• Add tests for Tab/TabBar

I made a little demo script with a scrolling TabBar alongside a wrapping one with a resizable window so the behavior can be easily tested (requires this branch). Testers should try changing autoarrange_subviews in the script and ensure it doesn't break things, play around with the options, and double check that existing consumers of this widget like launcher and control-panel doesn't get messed up in some way that I missed.

Some notes on the expected behavior:

• If the window is resized while the tabs are scrolled to the right, it will just reset the scroll offset back to 0
• The scroll left/scroll right buttons should only be shown when needed. If resizing the window, the scroll right button should disappear as soon as the last tab is fully in view
• When switching tabs with hotkeys or by clicking, the selected tab should be scrolled into view + a slight (customizable) offset to show part of the next tab. The default offset seems generally appropriate but didn't work well with a TabBar with a small width, so I made it possible to customize it.

[robob27]

pre-commit.ci autofix

[robob27]

I should probably make it possible to customize the colors of the scroll labels as well 🤔 Done.

[myk002]

As a matter of style consistency, I don't think this should be configurable. I think players would expect this to be constant in all situations where it appears.

I also suggest making the horizontal scroll icon look more like this:

perhaps with only one left/right triangle if two triangles stacked vertically doesn't fit well. The code for that example screen is here:

• widget: https://github.com/DFHack/dfhack/blob/develop/plugins/lua/sort.lua#L1144
• characters: https://github.com/DFHack/dfhack/blob/develop/plugins/lua/sort.lua#L1015

[robob27]

Ah yeah that's a much nicer symbol. Will fix!

[myk002]

This looks awesome! Thank you!

Scrolling is very important to get right. Could you add some unit tests in test/library/gui/widgets.TabBar.lua (need to create a new file, but can be based on test/library/gui/widgets.Scrollbar.lua)

[robob27]

@myk002 Added a bunch of tests for the new scroll behavior as well as some tests for existing behavior. I think I covered pretty much everything? But let me know if you see something I missed and I'm happy to add it 😄