feat(donut): mark group slices with an outward chevron

docs/ARCHITECTURE.md

@@ -155,7 +155,8 @@ The editor's Front / Back switch (`ToolbarPageViewModel.EditingBack`) edits eith
 A group is one slice that opens up to six non-group actions. Its members may be conversions or interactive tools
 (for example the PDF Edit group contains Crop and the page editor); groups cannot contain another group. The group
 editor offers both kinds, and `UserDataStore.EnsureConsistency` removes missing, duplicate, nested or excess members
-without excluding tools.
+without excluding tools. A group slice is marked with a small chevron by its outer edge, drawn in the slice's transform
+(`DonutMenu.DrawGroupMark`), which also marks a dragged group in the toolbar editor.
 
 ## Annotate tool
 

src/Filee.App/Controls/DonutMenu.Progress.cs

@@ -294,8 +294,7 @@ private void RenderProgress(DrawingContext context, Point center, double r1, dou
                     if (hot)
                         context.DrawGeometry(WithOpacity(AccentBrush, 0.8), null, wedge);
                     // Labels shrink with their slice instead of vanishing when the collapse starts.
-                    DrawLabel(context, Items![i], center, (r1 + r2) / 2, DonutGeometry.MidAngle(i, n),
-                        DonutGeometry.Span(n) * (r1 + r2) / 2 - 10, r2 - r1 - 16, bold, regular, hot);
+                    DrawSliceLabel(context, Items![i], center, r1, r2, DonutGeometry.MidAngle(i, n), DonutGeometry.Span(n), bold, regular, hot);
                 }
             }
 

src/Filee.App/Controls/DonutMenu.cs

@@ -52,7 +52,7 @@ public sealed partial class DonutMenu : Control
     public static readonly StyledProperty<IReadOnlyList<DonutItem>?> ItemsProperty =
         AvaloniaProperty.Register<DonutMenu, IReadOnlyList<DonutItem>?>(nameof(Items));
     public static readonly StyledProperty<double> OuterRadiusProperty =
-        AvaloniaProperty.Register<DonutMenu, double>(nameof(OuterRadius), 150);
+        AvaloniaProperty.Register<DonutMenu, double>(nameof(OuterRadius), DefaultOuterRadius);
     public static readonly StyledProperty<double> HoleRatioProperty =
         AvaloniaProperty.Register<DonutMenu, double>(nameof(HoleRatio), 0.42);
     public static readonly StyledProperty<double> SliceOpacityProperty =
@@ -125,6 +125,8 @@ public sealed partial class DonutMenu : Control
     private int _previewSlot = -1;
     private int _previewRemoved = -1;
     private string? _previewLabel;
+    private bool _previewGroup;
+    internal bool PreviewIsGroup => _previewGroup;
     private (int Index, Point Start, PointerPressedEventArgs Args)? _press;
 
     static DonutMenu()
@@ -294,11 +296,11 @@ public void SetDropTarget(int index)
     /// <summary>
     /// Edit mode: opens a gap at <paramref name="slot"/> (the position in the list after the drop) and shows a
     /// translucent slice labelled <paramref name="label"/> there. <paramref name="removed"/> is the slice being moved,
-    /// which leaves its place. -1 closes the gap.
+    /// which leaves its place. -1 closes the gap. <paramref name="group"/>: the slice is a group, and marked as one.
     /// </summary>
-    public void SetDropPreview(int slot, string? label = null, int removed = -1)
+    public void SetDropPreview(int slot, string? label = null, int removed = -1, bool group = false)
     {
-        if (_previewSlot == slot && _previewRemoved == removed && _previewLabel == label)
+        if (_previewSlot == slot && _previewRemoved == removed && _previewLabel == label && _previewGroup == group)
             return;
         if (_previewSlot < 0 && slot >= 0)
         {
@@ -309,6 +311,7 @@ public void SetDropPreview(int slot, string? label = null, int removed = -1)
         _previewSlot = slot;
         _previewRemoved = removed;
         _previewLabel = label;
+        _previewGroup = group;
         StartAnimation();
     }
 
@@ -900,8 +903,7 @@ private void RenderRing(DrawingContext context, Point center, double r1, double
                     context.DrawGeometry(WithOpacity(AccentBrush, 0.82 * Math.Clamp(emphasis, 0, 1)), null, wedge);
 
                 var hot = (i == ActiveIndex || i == _dropTargetIndex) && item.IsEnabled;
-                DrawLabel(context, item, center, (r1 + r2) / 2, mid, span * (r1 + r2) / 2 - 10,
-                    r2 - r1 - 16, typeface, typefaceRegular, hot);
+                DrawSliceLabel(context, item, center, r1, r2, mid, span, typeface, typefaceRegular, hot);
             }
         }
 
@@ -925,8 +927,7 @@ private void RenderRing(DrawingContext context, Point center, double r1, double
                     context.DrawGeometry(WithOpacity(SliceBrush, SliceOpacity * (slice.Item.IsEnabled ? 1 : 0.55)), BorderPen(), wedge);
                     if (slice.Emphasis > 0.01 && slice.Item.IsEnabled)
                         context.DrawGeometry(WithOpacity(AccentBrush, 0.82 * Math.Clamp(slice.Emphasis, 0, 1)), null, wedge);
-                    DrawLabel(context, slice.Item, center, (r1 + r2) / 2, slice.Mid,
-                        slice.Span * (r1 + r2) / 2 - 10, r2 - r1 - 16, typeface, typefaceRegular,
+                    DrawSliceLabel(context, slice.Item, center, r1, r2, slice.Mid, slice.Span, typeface, typefaceRegular,
                         slice.Hot && slice.Item.IsEnabled);
                 }
             }
@@ -1080,6 +1081,54 @@ private void DrawLabel(DrawingContext context, DonutItem item, Point center, dou
             DrawCentered(context, caption, anchor.X, y + label.Height);
     }
 
+    /// <summary>A slice's name and caption, and a group's mark, the name moved in to leave the mark room.</summary>
+    private void DrawSliceLabel(DrawingContext context, DonutItem item, Point center, double r1, double r2, double mid,
+        double span, Typeface bold, Typeface regular, bool hot)
+    {
+        var room = item.IsGroup ? GroupMarkRoom * GroupMarkScale : 0;
+        DrawLabel(context, item, center, (r1 + r2 - room) / 2, mid, span * (r1 + r2) / 2 - 10, r2 - r1 - 16, bold, regular, hot);
+        DrawGroupMark(context, item, center, r2, mid, hot);
+    }
+
+    /// <summary>
+    /// A group slice's mark: a small chevron by its outer edge pointing outward, where its ring fans out, as a
+    /// submenu's ▸ points to where it opens. Drawn inside the slice's transform, it opens, pops out and flips with it.
+    /// </summary>
+    private void DrawGroupMark(DrawingContext context, DonutItem item, Point center, double r2, double mid, bool hot)
+    {
+        if (!item.IsGroup)
+            return;
+        var brush = hot ? OnAccentBrush : SecondaryForeground;
+        if (brush is null)
+            return;
+        var size = GroupMarkScale;
+        var inset = GroupMarkInset * size;
+        var tip = DonutGeometry.PointAt(center, r2 - inset, mid);
+        var back = r2 - inset - GroupMarkDepth * size;
+        // The arms' ends sit GroupMarkHalfWidth to either side of the slice's middle line.
+        var turn = GroupMarkHalfWidth * size / back;
+        var pen = new Pen(brush, GroupMarkStroke * size, lineCap: PenLineCap.Round, lineJoin: PenLineJoin.Round);
+        var mark = new StreamGeometry();
+        using (var g = mark.Open())
+        {
+            g.BeginFigure(DonutGeometry.PointAt(center, back, mid - turn), false);
+            g.LineTo(tip);
+            g.LineTo(DonutGeometry.PointAt(center, back, mid + turn));
+            g.EndFigure(false);
+        }
+        using (context.PushOpacity(item.IsEnabled ? 1 : 0.5))
+            context.DrawGeometry(null, pen, mark);
+    }
+
+    /// <summary>The group mark's size follows the donut's: 1 at the default radius.</summary>
+    private double GroupMarkScale => OuterRadius / DefaultOuterRadius;
+
+    private const double DefaultOuterRadius = 150;
+
+    // The group mark at the default radius: its tip this far in from the outer edge, its arms this far back and this
+    // far to each side, its line this thick, and how far a group's text area gives way for it.
+    private const double GroupMarkInset = 7, GroupMarkDepth = 4.5, GroupMarkHalfWidth = 5, GroupMarkStroke = 1.6, GroupMarkRoom = 6;
+
     /// <summary>
     /// A slice's caption under its name: one line, or two where the slice is deep enough, so a caption wider than the
     /// slice ("Same format" on a small donut) wraps instead of ending in "Same for…".
@@ -1209,8 +1258,8 @@ private void DrawPreview(DrawingContext context, Point center, double r1, double
         if (_previewLabel is null || span < 0.25)
             return;
         using (context.PushOpacity(Math.Clamp((span - 0.25) / 0.3, 0, 1) * 0.9))
-            DrawLabel(context, new DonutItem { Id = "", Label = _previewLabel }, center, (r1 + r2) / 2, mid,
-                span * (r1 + r2) / 2 - 10, r2 - r1 - 16, bold, regular, hot: false);
+            DrawSliceLabel(context, new DonutItem { Id = "", Label = _previewLabel, Children = _previewGroup ? [] : null }, center,
+                r1, r2, mid, span, bold, regular, hot: false);
     }
 
     /// <summary>

src/Filee.App/ViewModels/Pages/ToolbarPageViewModel.cs

@@ -62,6 +62,7 @@ public sealed record PaletteChip(string PresetId, string Label, string? Caption,
     public bool IsDimmed => Use != PresetUse.Usable;
     public bool CanAdd => Use != PresetUse.Unusable;
     public object? Tip { get; init; }
+    public bool IsGroup { get; init; }
 }
 
 public sealed partial class ToolbarPageViewModel : ObservableObject, IDisposable
@@ -699,7 +700,9 @@ private void Rebuild()
         DonutItems = used
             .Select(_store.FindPreset)
             .OfType<Preset>()
-            .Select(p => new DonutItem { Id = p.Id, Label = _loc.DonutName(p), Caption = Caption(p) })
+            // A group is marked as one (no children: the editor doesn't fan them out), so the preview draws it as the
+            // donut does.
+            .Select(p => new DonutItem { Id = p.Id, Label = _loc.DonutName(p), Caption = Caption(p), Children = p.IsGroup ? [] : null })
             .ToList();
 
         Palette.Clear();
@@ -746,7 +749,7 @@ private void Rebuild()
             if (caption is not null && label.Contains(caption, StringComparison.OrdinalIgnoreCase))
                 caption = null;
             var chip = new PaletteChip(preset.Id, label, caption, reason, use)
-            { Tip = TipFor(preset, use, reason) };
+            { Tip = TipFor(preset, use, reason), IsGroup = preset.IsGroup };
             if (use != PresetUse.Unusable)
                 Palette.Add(chip);
             if ((query.Length == 0 && use != PresetUse.Unusable)
@@ -843,7 +846,7 @@ private void RefreshVisiblePalette()
                 && caption?.Contains(query, StringComparison.CurrentCultureIgnoreCase) != true)
                 continue;
             candidates.Add((new PaletteChip(preset.Id, label, caption, judgement.Reason, judgement.Use)
-            { Tip = TipFor(preset, judgement.Use, judgement.Reason) },
+            { Tip = TipFor(preset, judgement.Use, judgement.Reason), IsGroup = preset.IsGroup },
                 preset.IsGroup ? PaletteTab.All : TabOf(preset), preset.IsGroup));
         }
         RefreshVisiblePalette(candidates);

src/Filee.App/Views/Pages/ToolbarPage.axaml.cs

@@ -29,8 +29,9 @@ public partial class ToolbarPage : UserControl
 
     private enum Source { Chip, Slice }
 
-    // CanAdd: fixed when the drag starts, so a chip that a search or a tab swaps under the pointer can't change it.
-    private sealed record DragState(Source Source, string? PresetId, int SliceIndex, string Label, Point Start, bool CanAdd = true)
+    // CanAdd, IsGroup: fixed when the drag starts, so a chip that a search or a tab swaps under the pointer, or slices
+    // that another profile replaces, can't change them.
+    private sealed record DragState(Source Source, string? PresetId, int SliceIndex, string Label, Point Start, bool CanAdd = true, bool IsGroup = false)
     {
         public bool Active { get; set; }
     }
@@ -63,7 +64,8 @@ public ToolbarPage()
             if (Vm is null || e.Index >= Vm.DonutItems.Count)
                 return;
             var p = e.Args.GetPosition(Root);
-            _drag = new DragState(Source.Slice, null, e.Index, Vm.DonutItems[e.Index].Label, p) { Active = true };
+            var item = Vm.DonutItems[e.Index];
+            _drag = new DragState(Source.Slice, null, e.Index, item.Label, p, IsGroup: item.IsGroup) { Active = true };
             Donut.SetDimmedIndex(e.Index);
             ShowGhost(_drag.Label, p);
         };
@@ -246,7 +248,7 @@ private void OnChipPressed(object? sender, PointerPressedEventArgs e)
         if (!point.Properties.IsLeftButtonPressed || !chip.CanAdd)
             return;
 
-        _drag = new DragState(Source.Chip, chip.PresetId, -1, chip.Label, e.GetPosition(Root), chip.CanAdd);
+        _drag = new DragState(Source.Chip, chip.PresetId, -1, chip.Label, e.GetPosition(Root), chip.CanAdd, chip.IsGroup);
         e.Pointer.Capture(border);
         e.Handled = true;
     }
@@ -291,7 +293,7 @@ private void OnRootPointerMoved(object? sender, PointerEventArgs e)
         ShowGhost(_drag.Label, p);
         var (sliceTarget, overPalette) = FindTarget(e);
         var removing = overPalette && _drag.Source == Source.Slice;
-        Donut.SetDropPreview(removing ? -1 : sliceTarget, _drag.Label, _drag.Source == Source.Slice ? _drag.SliceIndex : -1);
+        Donut.SetDropPreview(removing ? -1 : sliceTarget, _drag.Label, _drag.Source == Source.Slice ? _drag.SliceIndex : -1, _drag.IsGroup);
         PaletteBox.Classes.Set("over", removing);
     }