[lightscape-jm]

What does this change?

Closes #870, closes #871, closes #872.

Why one PR for three issues (agreed in #870). All three change how a donut's text is laid out. #870 sets the rules (the safe zone, one name size per ring, when to shorten, icons and captions). #871 changes the shape of a group's ring, and #872 picks the direction of the ring's names from that shape. Tuned one at a time, each would have needed retuning when the next landed, and a donut change from someone else in between would have meant a third pass. There are six commits: one per issue, in order (#870, #871, #872), so each can be read or reverted apart; then one that retunes the rules for all three together, from renders with the app's own fonts; one that adds short donut names where German and English were cut; and one that splits the two layout sweeps into a test case per language, so each stays under CI's five-minute hang limit.

#870: labels that stay inside their slice

• Safe zone. Every name, caption and icon stays inside its slice, clear of the edges, the hole and a group's chevron. Today a long name runs over the edge or the chevron in German, Japanese and Chinese (screenshots). The margin is kept from the letters themselves (their outlines, each line at its own width), about the room today's donut leaves, so where today fits a name, this PR places it the same way: on the slice's middle, with its caption.
• Centred. A name goes on its slice's middle first, moved sideways to as much room left of it as right (a slice that runs aslant has more on one side), and drops a caption it doesn't need before it moves. Lines wrap at today's width. A group slice keeps its label clear of the chevron itself, not of a band across the slice, so its label is centred as any other's.
• One name size per ring, 13 px at the default size. A name that doesn't fit is shortened with "…" rather than every name made smaller; the centre names the slice under the pointer in full (DonutItem.FullName). The ring steps down half a pixel at a time only where a name would otherwise be cut by just a letter or two, or so short it no longer reads, or (in Icon & text) to keep an icon above every name.
• Short donut names for long translations. Where a default donut cut a name, a short form goes in the catalogs (preset.<name>.donut, as Half size and Pixelate already have): German "Freistellen", "Kleiner machen", "PDF verbinden", "Ohne Metadaten"…, English "Compress" and "Cut out". The other languages carry the same keys with their full names, for translators to shorten.
• Icons and Show modes. A curated set of Material Design Icons. Each donut has a Show mode (Settings → Donut toolbar), and a preset can override it: Auto (icon above the name where every slice of the ring has room for both and loses nothing for it, neither a caption nor its place on the middle; else names), Icon & text, Text only, Icon only. Icon & text keeps its icons: where an icon and its name don't fit (the eight-slice back faces), the ring's names step down rather than be cut to a word ("Merge…"); a slice set to Icon only or Text only, or given a short name, lets them keep their size. Plain format conversions have no icon; their name is their label.
• Captions show per slice, where they fit under the name, beside an icon too. The two that tell slices apart ([Feature]: Donut: a switch to hide the output format under slice names #869: "Copy to folder" / "Move to folder", and the format under two slices of one name) stay with Show output format off, and two slices of one name always look alike.
• Short name and icon per preset in the preset and group editors; Label scale per donut.

#871: group rings that follow the donut

The ring grows and shrinks with the donut, and two settings in Appearance set its size (75–150 %) and how far it spreads (100–300 %). Every group's ring slices are equally wide.

#872: names along the ring

On a group's ring, names bend along the curve where the ring is wide and run out from the centre where it's deep, one direction for the ring. Scripts whose letters join or reorder (Arabic, Persian, Thai, the Indic scripts) are drawn level with the ring instead of bent, and Chinese, Japanese and Korean stay upright. A preset's Text direction (Straight, Out from the centre, Along the ring) overrides it, on the donut's face too; the face's own names stay upright by default (turned, they read sideways on the top and bottom slices; bent, they lose their caption line). Where a name is bent its icon sits above it as read; on a ring's chips, too shallow for that, beside it.

Screenshots

Faces (today on top, this PR below): English, German, Japanese and Chinese. Where today fits a name, it sits where it did; where today runs over an edge or cuts a word, it doesn't.

Group rings: today, then this PR at the default ring, at ring size 150 % and at spread 200 %, in English, Japanese and Arabic.

Show modes on the image and PDF back faces: Auto, Icon & text, Text only, Icon only, and Auto with Show output format off.

Names along the ring (#872): wide group rings bend their names; a face whose presets are set to Along the ring bends its top and bottom names.

Branched from current main (f4038aa).

Type of change

• Bug fix
• New feature or improvement
• New format or engine
• Translation
• Documentation
• Build, CI or dependencies

How was it tested?

• dotnet format --verify-no-changes --severity warn
• dotnet test on macOS: Core 1,246 passed; App 2,351 passed. The 2 App tests that fail also fail on unmodified main on my Mac (RenderTests.Engines_page_shows_versions…, DonutHighlightTests.A_lost_animation_frame…).
• Linux (Docker, Ubuntu 24.04, the app's fonts): App label, donut, ring, toolbar and translation tests, 668 passed. Core 1,247 passed; FolderCopyTests.Original_that_cannot_be_deleted… fails there as root, on unmodified main too.
• Windows 11 ARM64: the same App tests, 668 passed; Core 1,244 passed.
• Layout sweeps in the tests over every built-in donut (front, back and every group's ring), three donut sizes, three Label scales, three ring sizes and spreads, the four Show modes, Show output format on and off and every language: SliceLabelFitTests (inside the safe zone, one size and direction per ring, Auto never mixes, same-named slices alike) and SliceLabelReadabilityTests (never cut where it has room whole, never a lesser style where every slice has room for more).
• Each rule added in the retune has a test that fails with the rule taken out (placement off the middle line, cuts by a letter or two, one long word, CJK upright on a ring, icons above bent names, same-named slices, needed captions, names shortened under an icon wrapping, the letters' margin, centring and its balance, the chevron, Auto icons that cost nothing).
• Every English face slice sits on its slice's middle with every caption today shows (SliceLabelFitTests.English_names_…).
• Rendered with the app's own fonts about 1,000 donuts in 10 languages (English, German, Japanese, Chinese, Korean, Arabic, Persian, Thai, Hindi, Bengali), reviewed against today's renders by reviewers working independently over several rounds; what they found is fixed or listed below.
• Not tried by hand in the app.

Trade-offs, on purpose: a caption drops where it doesn't fit under its name at the ring's size (today the name shrinks for it); Label scale grows the names only where the slices have room for it; Thai has no spaces, so a long Thai name is shortened rather than wrapped; in Icon & text, one long word beside its icon ("Compress" on the PDF back face) and a bent two-line name under its icon ("Remove background" on a face set to Along the ring) are shortened, as there's no room to wrap them there.

Already so on main, not changed here: the centre says "1 files" and "1 × Folder" (untranslated); the German hint "Tab Vorderseite" is cut to "Tab Vorder…".

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