[Feature]: Donut: mark group slices with a small outward chevron #868

What would you like Filee to do?

Draw a small chevron by the outer edge of every group slice, pointing outward, to where its ring of presets fans out. A preset slice gets nothing; a group is recognisable at a glance, in any language and at any donut size.

Why / when would you use it?

Groups are one of the donut's best features, and with #806's "one or two group slices by default" more people will meet them. But today the only thing that tells a group from a preset is the "Group of N" caption:

• It's text to read, in a small size, under the name.
• A small or crowded donut has no room for it, and then nothing says the slice opens more.
• A slice that opens something when the pointer reaches it, with no sign it will, is a surprise.

A chevron is the convention people already know for "this opens more, over there": a submenu's ▸, and Blender's pie-menu sub-menu marker.

Ideas for how it could work

1. On group slices only, by the slice's outer edge, pointing out from the centre (where the ring opens).
2. It moves with its slice: drawn in the slice's own transform, so it opens, pops out on hover, flips with Tab and collapses into the progress ring together with the slice.
3. Colours: the secondary text colour, the highlight's text colour when the slice is lit (right), faded when the group is disabled. It follows the theme and custom themes.
4. The Donut toolbar page's preview marks its group slices too, so the editor and the donut agree.
5. No setting. It's a small mark on groups only; "Group of N" stays as it is.

Related

• Show output format ([Feature]: Donut: a switch to hide the output format under slice names #869) builds on this: with captions hidden, "Group of N" goes too and the chevron is what still marks a group.
• Slice icons and labels ([Feature]: Donut: slice icons, Show modes, and labels that stay inside their slice #870) keeps every label clear of the chevron.
• [Feature]: A rule for what Filee shows by default, before more formats are added #806 (group slices on the default donuts) is where this helps most.

Status

Working code: I built and tested this on Filee 2.2.0, then rebased it onto current main, where it builds and its tests pass. The screenshots above are from that build, rendered by the UI tests. It would be one small PR.