Add enhancements to progress widget

* Adds TransferSpeedColumn
* Adds DownloadedColumn
* Adds ElapsedTimeColumn
* Minor enhancements to existing columns

src/Spectre.Console/Extensions/Progress/SpinnerColumnExtensions.cs

@@ -23,5 +23,40 @@ namespace Spectre.Console
             column.Style = style;
             return column;
         }
+
+        /// <summary>
+        /// Sets the text that should be shown instead of the spinner
+        /// once a task completes.
+        /// </summary>
+        /// <param name="column">The column.</param>
+        /// <param name="text">The text.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        public static SpinnerColumn CompletedText(this SpinnerColumn column, string? text)
+        {
+            if (column is null)
+            {
+                throw new ArgumentNullException(nameof(column));
+            }
+
+            column.CompletedText = text;
+            return column;
+        }
+
+        /// <summary>
+        /// Sets the completed style of the spinner.
+        /// </summary>
+        /// <param name="column">The column.</param>
+        /// <param name="style">The style.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        public static SpinnerColumn CompletedStyle(this SpinnerColumn column, Style? style)
+        {
+            if (column is null)
+            {
+                throw new ArgumentNullException(nameof(column));
+            }
+
+            column.CompletedStyle = style;
+            return column;
+        }
     }
 }

src/Spectre.Console/Internal/FileSize.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Globalization;
+
+namespace Spectre.Console.Internal
+{
+    internal struct FileSize
+    {
+        public double Bytes { get; }
+        public FileSizeUnit Unit { get; }
+        public string Suffix => GetSuffix();
+
+        public FileSize(double bytes)
+        {
+            Bytes = bytes;
+            Unit = Detect(bytes);
+        }
+
+        public FileSize(double bytes, FileSizeUnit unit)
+        {
+            Bytes = bytes;
+            Unit = unit;
+        }
+
+        public string Format(CultureInfo? culture = null)
+        {
+            var @base = GetBase(Unit);
+            if (@base == 0)
+            {
+                @base = 1;
+            }
+
+            var bytes = Bytes / @base;
+
+            return Unit == FileSizeUnit.Bytes
+                ? ((int)bytes).ToString(culture ?? CultureInfo.InvariantCulture)
+                : bytes.ToString("F1", culture ?? CultureInfo.InvariantCulture);
+        }
+
+        public override string ToString()
+        {
+            return ToString(suffix: true, CultureInfo.InvariantCulture);
+        }
+
+        public string ToString(bool suffix = true, CultureInfo? culture = null)
+        {
+            if (suffix)
+            {
+                return $"{Format(culture)} {Suffix}";
+            }
+
+            return Format(culture);
+        }
+
+        private string GetSuffix()
+        {
+            return (Bytes, Unit) switch
+            {
+                (_, FileSizeUnit.KiloByte) => "KB",
+                (_, FileSizeUnit.MegaByte) => "MB",
+                (_, FileSizeUnit.GigaByte) => "GB",
+                (_, FileSizeUnit.TeraByte) => "TB",
+                (_, FileSizeUnit.PetaByte) => "PB",
+                (_, FileSizeUnit.ExaByte) => "EB",
+                (_, FileSizeUnit.ZettaByte) => "ZB",
+                (_, FileSizeUnit.YottaByte) => "YB",
+                (1, _) => "byte",
+                (_, _) => "bytes",
+            };
+        }
+
+        private static FileSizeUnit Detect(double bytes)
+        {
+            foreach (var unit in (FileSizeUnit[])Enum.GetValues(typeof(FileSizeUnit)))
+            {
+                if (bytes < (GetBase(unit) * 1024))
+                {
+                    return unit;
+                }
+            }
+
+            return FileSizeUnit.Bytes;
+        }
+
+        private static double GetBase(FileSizeUnit unit)
+        {
+            return Math.Pow(1024, (int)unit);
+        }
+    }
+}

src/Spectre.Console/Internal/FileSizeUnit.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace Spectre.Console.Internal
+{
+    internal enum FileSizeUnit
+    {
+        Bytes = 0,
+        KiloByte = 1,
+        MegaByte = 2,
+        GigaByte = 3,
+        TeraByte = 4,
+        PetaByte = 5,
+        ExaByte = 6,
+        ZettaByte = 7,
+        YottaByte = 8,
+    }
+}

src/Spectre.Console/Widgets/Progress/Columns/DownloadedColumn.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Globalization;
+using Spectre.Console.Internal;
+using Spectre.Console.Rendering;
+
+namespace Spectre.Console
+{
+    /// <summary>
+    /// A column showing download progress.
+    /// </summary>
+    public sealed class DownloadedColumn : ProgressColumn
+    {
+        /// <summary>
+        /// Gets or sets the <see cref="CultureInfo"/> to use.
+        /// </summary>
+        public CultureInfo? Culture { get; set; }
+
+        /// <inheritdoc/>
+        public override IRenderable Render(RenderContext context, ProgressTask task, TimeSpan deltaTime)
+        {
+            var total = new FileSize(task.MaxValue);
+
+            if (task.IsFinished)
+            {
+                return new Markup(string.Format(
+                    "[green]{0} {1}[/]",
+                    total.Format(Culture),
+                    total.Suffix));
+            }
+            else
+            {
+                var downloaded = new FileSize(task.Value, total.Unit);
+
+                return new Markup(string.Format(
+                    "{0}[grey]/[/]{1} [grey]{2}[/]",
+                    downloaded.Format(Culture),
+                    total.Format(Culture),
+                    total.Suffix));
+            }
+        }
+    }
+}

src/Spectre.Console/Widgets/Progress/Columns/ElapsedTimeColumn.cs

@@ -0,0 +1,37 @@
+using System;
+using Spectre.Console.Rendering;
+
+namespace Spectre.Console
+{
+    /// <summary>
+    /// A column showing the elapsed time of a task.
+    /// </summary>
+    public sealed class ElapsedTimeColumn : ProgressColumn
+    {
+        /// <inheritdoc/>
+        protected internal override bool NoWrap => true;
+
+        /// <summary>
+        /// Gets or sets the style of the remaining time text.
+        /// </summary>
+        public Style Style { get; set; } = new Style(foreground: Color.Blue);
+
+        /// <inheritdoc/>
+        public override IRenderable Render(RenderContext context, ProgressTask task, TimeSpan deltaTime)
+        {
+            var elapsed = task.ElapsedTime;
+            if (elapsed == null)
+            {
+                return new Markup("-:--:--");
+            }
+
+            return new Text($"{elapsed.Value:h\\:mm\\:ss}", Style ?? Style.Plain);
+        }
+
+        /// <inheritdoc/>
+        public override int? GetColumnWidth(RenderContext context)
+        {
+            return 7;
+        }
+    }
+}

src/Spectre.Console/Widgets/Progress/Columns/SpinnerColumn.cs

@@ -16,6 +16,7 @@ namespace Spectre.Console
         private readonly object _lock;
         private Spinner _spinner;
         private int? _maxWidth;
+        private string? _completed;
 
         /// <inheritdoc/>
         protected internal override bool NoWrap => true;
@@ -36,6 +37,25 @@ namespace Spectre.Console
             }
         }
 
+        /// <summary>
+        /// Gets or sets the text that should be shown instead
+        /// of the spinner once a task completes.
+        /// </summary>
+        public string? CompletedText
+        {
+            get => _completed;
+            set
+            {
+                _completed = value;
+                _maxWidth = null;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the completed style.
+        /// </summary>
+        public Style? CompletedStyle { get; set; }
+
         /// <summary>
         /// Gets or sets the style of the spinner.
         /// </summary>
@@ -67,7 +87,7 @@ namespace Spectre.Console
 
             if (!task.IsStarted || task.IsFinished)
             {
-                return new Markup(new string(' ', GetMaxWidth(context)));
+                return new Markup(CompletedText ?? " ", CompletedStyle ?? Style.Plain);
             }
 
             var accumulated = task.State.Update<double>(ACCUMULATED, acc => acc + deltaTime.TotalMilliseconds);
@@ -97,7 +117,9 @@ namespace Spectre.Console
                     var useAscii = (context.LegacyConsole || !context.Unicode) && _spinner.IsUnicode;
                     var spinner = useAscii ? Spinner.Known.Ascii : _spinner ?? Spinner.Known.Default;
 
-                    _maxWidth = spinner.Frames.Max(frame => Cell.GetCellLength(context, frame));
+                    _maxWidth = Math.Max(
+                        ((IRenderable)new Markup(CompletedText ?? " ")).Measure(context, int.MaxValue).Max,
+                        spinner.Frames.Max(frame => Cell.GetCellLength(context, frame)));
                 }
 
                 return _maxWidth.Value;

src/Spectre.Console/Widgets/Progress/Columns/TransferSpeedColumn.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Globalization;
+using Spectre.Console.Internal;
+using Spectre.Console.Rendering;
+
+namespace Spectre.Console
+{
+    /// <summary>
+    /// A column showing transfer speed.
+    /// </summary>
+    public sealed class TransferSpeedColumn : ProgressColumn
+    {
+        /// <summary>
+        /// Gets or sets the <see cref="CultureInfo"/> to use.
+        /// </summary>
+        public CultureInfo? Culture { get; set; }
+
+        /// <inheritdoc/>
+        public override IRenderable Render(RenderContext context, ProgressTask task, TimeSpan deltaTime)
+        {
+            if (task.Speed == null)
+            {
+                return new Text("?/s");
+            }
+
+            var size = new FileSize(task.Speed.Value);
+            return new Markup(string.Format("{0}/s", size.ToString(suffix: true, Culture)));
+        }
+    }
+}

src/Spectre.Console/Widgets/Progress/ProgressTask.cs

@@ -89,7 +89,14 @@ namespace Spectre.Console
         /// </summary>
         public TimeSpan? RemainingTime => GetRemainingTime();
 
-        internal ProgressTask(int id, string description, double maxValue, bool autoStart)
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ProgressTask"/> class.
+        /// </summary>
+        /// <param name="id">The task ID.</param>
+        /// <param name="description">The task description.</param>
+        /// <param name="maxValue">The task max value.</param>
+        /// <param name="autoStart">Whether or not the task should start automatically.</param>
+        public ProgressTask(int id, string description, double maxValue, bool autoStart = true)
         {
             _samples = new List<ProgressSample>();
             _lock = new object();