Fix #65: Add Previous and Next buttons to sliders

This change adds previous and next buttons the FontGlyphsView slider.

Controls:
- Add generic Layout and LayoutManager
- Add Toolbar and ToolbarLayoutManager
- Add SliderView
Converter:
- Add generic TypeConverter base class.

FontFamily:
- Rename DefaultFontFamily to Defauilt
- Rename FluentUIFontFamily to FluentUI

GlyphsView:
- Replace Slider with SliderView

SkLabel:
- Integrate FontFamily changes
- Fix #endregion labels

Slider:
- Fix OnPropertyChanged implementation.
- use Math.Clamp in ValueProperty coerceValue

Author: DanTravison

Controls/Layouts/Layout.cs

@@ -0,0 +1,243 @@
+namespace GlyphViewer.Controls.Layouts;
+
+/// <summary>
+/// Provides an abstract base <see cref="Layout"/> class.
+/// </summary>
+/// <typeparam name="I">The type of <see cref="LayoutInfo"/> to use to layout child items.</typeparam>
+public abstract class Layout<I> : Layout
+    where I : LayoutInfo
+{
+    #region Fields
+
+    readonly Dictionary<IView, I> _layoutInfo = new(ReferenceEqualityComparer.Instance);
+    Size _measuredSize = Size.Zero;
+
+    #endregion Fields
+
+    /// <summary>
+    /// Initializes a new instance of this class.
+    /// </summary>
+    protected Layout()
+    { }
+
+    #region Properties
+
+    /// <summary>
+    /// Gets the <typeparamref name="I"/> <see cref="Info"/> for the specified <paramref name="view"/> view.
+    /// </summary>
+    /// <param name="view">The <see cref="IView"/> of information to retrieve.</param>
+    /// <returns>The <typeparamref name="I"/> <see cref="Info"/>, if found; otherwise, a null reference.</returns>
+    public I this[IView view]
+    {
+        get
+        {
+            _layoutInfo.TryGetValue(view, out I info);
+            return info;
+        }
+    }
+
+    /// <summary>
+    /// Enumerates the <typeparamref name="I"/> <see cref="LayoutInfo"/> for each view.
+    /// </summary>
+    /// <returns>An <see cref="IEnumerable{T}"/>.</returns>
+    protected IEnumerable<I> Info
+    {
+        get => _layoutInfo.Values;
+    }
+
+    #endregion Properties
+
+    #region Add
+
+    void AddView(IView view)
+    {
+        I info = CreateItemInfo(view);
+        if (info is not null)
+        {
+            _layoutInfo.Add(view, info);
+            OnItemAdded(info);
+        }
+    }
+
+    /// <summary>
+    /// Creates an instance of <typeparamref name="I"/> <see cref="LayoutInfo"/>.
+    /// </summary>
+    /// <param name="view">The <see cref="IView"/> to arrange.</param>
+    /// <returns>A new instance of a <typeparamref name="I"/> <see cref="LayoutInfo"/>.</returns>
+    protected abstract I CreateItemInfo(IView view);
+
+    /// <summary>
+    /// Overridden in the derived class when a <see cref="IView"/> is added.
+    /// </summary>
+    /// <param name="info">The <typeparamref name="I"/> for the added view.</param>
+    protected virtual void OnItemAdded(I info)
+    {
+    }
+
+    #endregion Add
+
+    #region Remove
+
+    void RemoveView(IView view)
+    {
+        if (_layoutInfo.TryGetValue(view, out I info))
+        {
+            _layoutInfo.Remove(view);
+            OnItemRemoved(info);
+            info.Removed();
+        }
+    }
+
+    /// <summary>
+    /// Overridden in the derived class when a <see cref="IView"/> is removed.
+    /// </summary>
+    /// <param name="info">The <typeparamref name="I"/> for the removed view.</param>
+    protected virtual void OnItemRemoved(I info)
+    {
+    }
+
+    #endregion Remove
+
+    #region Find
+
+    /// <summary>
+    /// Find the <typeparamref name="I"/> <see cref="LayoutInfo"/> for the item 
+    /// at the specified <paramref name="point"/>.
+    /// </summary>
+    /// <param name="point">The <see cref="Point"/> to query.</param>
+    /// <returns>
+    /// The <typeparamref name="I"/> <see cref="LayoutInfo"/> for the item 
+    /// at the specified <paramref name="point"/>; otherwise, a null reference.
+    /// </returns>
+    public I Find(Point point)
+    {
+        foreach (I info in _layoutInfo.Values)
+        {
+            if (info.Bounds.Contains(point))
+            {
+                return info;
+            }
+        }
+        return null;
+    }
+
+    /// <summary>
+    /// Find the child <see cref="View"/> at the specified <paramref name="point"/>.
+    /// </summary>
+    /// <param name="point">The <see cref="Point"/> to query.</param>
+    /// <returns>
+    /// The <see cref="View"/> for the child at the specified <paramref name="point"/>;
+    /// otherwise, a null reference.
+    /// </returns>
+    public View FindChild(Point point)
+    {
+        if (Find(point) is I info)
+        {
+            return info.View as View;
+        }
+        return null;
+    }
+
+    #endregion Find
+
+    #region Overrides
+
+    /// <summary>
+    /// Updates the size of an View.
+    /// </summary>
+    /// <param name="widthConstraint">The width that a parent element can allocate a child element.</param>
+    /// <param name="heightConstraint">The height that a parent element can allocate a child element.</param>
+    /// <returns>The desired Size for this element.</returns>
+    protected override Size MeasureOverride(double widthConstraint, double heightConstraint)
+    {
+        bool needsMeasure = _measuredSize.Width != widthConstraint || _measuredSize.Height != heightConstraint;
+        if (needsMeasure)
+        {
+            foreach (LayoutInfo info in _layoutInfo.Values)
+            {
+                info.View.InvalidateMeasure();
+            }
+        }
+        else
+        {
+            foreach (LayoutInfo info in _layoutInfo.Values)
+            {
+                if (info.NeedsMeasure)
+                {
+                    needsMeasure = true;
+                    break;
+                }
+            }
+        }
+        if (needsMeasure)
+        {
+            _measuredSize = base.MeasureOverride(widthConstraint, heightConstraint);
+        }
+        return _measuredSize;
+    }
+
+    /// <summary>
+    /// Adds an <see cref="IView"/> to the <see cref="Layout.Children"/> collection.
+    /// </summary>
+    /// <param name="index">The zero-based index to add.</param>
+    /// <param name="view">The <see cref="IView"/> to add.</param>
+    protected override sealed void OnAdd(int index, IView view)
+    {
+        base.OnAdd(index, view);
+        AddView(view);
+        InvalidateMeasure();
+    }
+
+    /// <summary>
+    /// Inserts an <see cref="IView"/> into the <see cref="Layout.Children"/> collection.
+    /// </summary>
+    /// <param name="index">The zero-based index to insert at.</param>
+    /// <param name="view">The <see cref="IView"/> to add.</param>
+    protected override sealed void OnInsert(int index, IView view)
+    {
+        base.OnInsert(index, view);
+        AddView(view);
+        InvalidateMeasure();
+    }
+
+    /// <summary>
+    /// Removes an <see cref="IView"/> from the <see cref="Layout.Children"/> collection.
+    /// </summary>
+    /// <param name="index">The zero-based index of the <see cref="IView"/> to remove.</param>
+    /// <param name="view">The <see cref="IView"/> to remove.</param>
+    protected override sealed void OnRemove(int index, IView view)
+    {
+        base.OnRemove(index, view);
+        RemoveView(view);
+        InvalidateMeasure();
+    }
+
+    /// <summary>
+    /// Replaces an <see cref="IView"/> in the <see cref="Layout.Children"/> collection.
+    /// </summary>
+    /// <param name="index">The zero-based index of the <see cref="IView"/> to update.</param>
+    /// <param name="view">The <see cref="IView"/> to set.</param>
+    /// <param name="oldView">The <see cref="IView"/> to replace.</param>
+    protected override sealed void OnUpdate(int index, IView view, IView oldView)
+    {
+        base.OnUpdate(index, view, oldView);
+        RemoveView(oldView);
+        AddView(view);
+        InvalidateMeasure();
+    }
+
+    /// <summary>
+    /// Removes all items from the <see cref="Layout.Children"/> collection.
+    /// </summary>
+    protected override sealed void OnClear()
+    {
+        base.OnClear();
+        foreach (I info in _layoutInfo.Values)
+        {
+            RemoveView(info.View);
+        }
+        InvalidateMeasure();
+    }
+
+    #endregion Overrides
+}