Allow custom instructions for prompts

Closes #229

docs/input/prompts/multiselection.md

@@ -16,6 +16,10 @@ var fruits = AnsiConsole.Prompt(
         .Title("What are your [green]favorite fruits[/]?")
         .NotRequired() // Not required to have a favorite fruit
         .PageSize(10)
+        .MoreChoicesText("[grey](Move up and down to reveal more fruits)[/]")
+        .InstructionsText(
+            "[grey](Press [blue]<space>[/] to toggle a fruit, " + 
+            "[green]<enter>[/] to accept)[/]")
         .AddChoice("Apple")
         .AddChoices(new[] {
             "Apricot", "Avocado", 

docs/input/prompts/selection.md

@@ -15,6 +15,7 @@ var fruit = AnsiConsole.Prompt(
     new SelectionPrompt<string>()
         .Title("What's your [green]favorite fruit[/]?")
         .PageSize(10)
+        .MoreChoicesText("[grey](Move up and down to reveal more fruits)[/]")
         .AddChoice("Apple")
         .AddChoices(new[] {
             "Apricot", "Avocado", 

examples/Console/Prompt/Program.cs

@@ -59,6 +59,7 @@ namespace Cursor
                 new MultiSelectionPrompt<string>()
                     .PageSize(10)
                     .Title("What are your [green]favorite fruits[/]?")
+                    .InstructionsText("[grey](Press [blue]<space>[/] to toggle a fruit, [green]<enter>[/] to accept)[/]")
                     .AddChoices(new[]
                     {
                         "Apple", "Apricot", "Avocado", "Banana", "Blackcurrant", "Blueberry",
@@ -88,8 +89,8 @@ namespace Cursor
 
             return AnsiConsole.Prompt(
                 new TextPrompt<string>("What's your [green]favorite sport[/]?")
-                    .InvalidChoiceMessage("[red]That's not a valid fruit[/]")
-                    .DefaultValue("Lol")
+                    .InvalidChoiceMessage("[red]That's not a sport![/]")
+                    .DefaultValue("Sport?")
                     .AddChoice("Soccer")
                     .AddChoice("Hockey")
                     .AddChoice("Basketball"));

src/Spectre.Console/Widgets/Prompt/MultiSelectionPrompt.cs

@@ -44,6 +44,16 @@ namespace Spectre.Console
         /// </summary>
         public Style? HighlightStyle { get; set; }
 
+        /// <summary>
+        /// Gets or sets the text that will be displayed if there are more choices to show.
+        /// </summary>
+        public string? MoreChoicesText { get; set; }
+
+        /// <summary>
+        /// Gets or sets the text that instructs the user of how to select items.
+        /// </summary>
+        public string? InstructionsText { get; set; }
+
         /// <summary>
         /// Gets or sets a value indicating whether or not
         /// at least one selection is required.
@@ -77,8 +87,11 @@ namespace Spectre.Console
             }
 
             var converter = Converter ?? TypeConverterHelper.ConvertToString;
+            var list = new RenderableMultiSelectionList<T>(
+                console, Title, PageSize, Choices,
+                Selected, converter, HighlightStyle,
+                MoreChoicesText, InstructionsText);
 
-            var list = new RenderableMultiSelectionList<T>(console, Title, PageSize, Choices, Selected, converter, HighlightStyle);
             using (new RenderHookScope(console, list))
             {
                 console.Cursor.Hide();

src/Spectre.Console/Widgets/Prompt/MultiSelectionPromptExtensions.cs

@@ -188,6 +188,42 @@ namespace Spectre.Console
             return obj;
         }
 
+        /// <summary>
+        /// Sets the text that will be displayed if there are more choices to show.
+        /// </summary>
+        /// <typeparam name="T">The prompt result type.</typeparam>
+        /// <param name="obj">The prompt.</param>
+        /// <param name="text">The text to display.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        public static MultiSelectionPrompt<T> MoreChoicesText<T>(this MultiSelectionPrompt<T> obj, string? text)
+        {
+            if (obj is null)
+            {
+                throw new ArgumentNullException(nameof(obj));
+            }
+
+            obj.MoreChoicesText = text;
+            return obj;
+        }
+
+        /// <summary>
+        /// Sets the text that instructs the user of how to select items.
+        /// </summary>
+        /// <typeparam name="T">The prompt result type.</typeparam>
+        /// <param name="obj">The prompt.</param>
+        /// <param name="text">The text to display.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        public static MultiSelectionPrompt<T> InstructionsText<T>(this MultiSelectionPrompt<T> obj, string? text)
+        {
+            if (obj is null)
+            {
+                throw new ArgumentNullException(nameof(obj));
+            }
+
+            obj.InstructionsText = text;
+            return obj;
+        }
+
         /// <summary>
         /// Requires no choice to be selected.
         /// </summary>

src/Spectre.Console/Widgets/Prompt/Rendering/RenderableMultiSelectionList.cs

@@ -8,9 +8,13 @@ namespace Spectre.Console
     {
         private const string Checkbox = "[[ ]]";
         private const string SelectedCheckbox = "[[X]]";
+        private const string MoreChoicesText = "[grey](Move up and down to reveal more choices)[/]";
+        private const string InstructionsText = "[grey](Press <space> to select, <enter> to accept)[/]";
 
         private readonly IAnsiConsole _console;
         private readonly string? _title;
+        private readonly Markup _moreChoices;
+        private readonly Markup _instructions;
         private readonly Style _highlightStyle;
 
         public HashSet<int> Selections { get; set; }
@@ -18,12 +22,15 @@ namespace Spectre.Console
         public RenderableMultiSelectionList(
             IAnsiConsole console, string? title, int pageSize,
             List<T> choices, HashSet<int> selections,
-            Func<T, string>? converter, Style? highlightStyle)
+            Func<T, string>? converter, Style? highlightStyle,
+            string? moreChoicesText, string? instructionsText)
             : base(console, pageSize, choices, converter)
         {
             _console = console ?? throw new ArgumentNullException(nameof(console));
             _title = title;
             _highlightStyle = highlightStyle ?? new Style(foreground: Color.Blue);
+            _moreChoices = new Markup(moreChoicesText ?? MoreChoicesText);
+            _instructions = new Markup(instructionsText ?? InstructionsText);
 
             Selections = new HashSet<int>(selections);
         }
@@ -93,10 +100,12 @@ namespace Spectre.Console
 
             if (scrollable)
             {
-                list.Add(new Markup("[grey](Move up and down to reveal more choices)[/]"));
+                // (Move up and down to reveal more choices)
+                list.Add(_moreChoices);
             }
 
-            list.Add(new Markup("[grey](Press <space> to select)[/]"));
+            // (Press <space> to select)
+            list.Add(_instructions);
 
             return new Rows(list);
         }

src/Spectre.Console/Widgets/Prompt/Rendering/RenderableSelectionList.cs

@@ -7,17 +7,23 @@ namespace Spectre.Console
     internal sealed class RenderableSelectionList<T> : RenderableList<T>
     {
         private const string Prompt = ">";
+        private const string MoreChoicesText = "[grey](Move up and down to reveal more choices)[/]";
 
         private readonly IAnsiConsole _console;
         private readonly string? _title;
+        private readonly Markup _moreChoices;
         private readonly Style _highlightStyle;
 
-        public RenderableSelectionList(IAnsiConsole console, string? title, int requestedPageSize, List<T> choices, Func<T, string>? converter, Style? highlightStyle)
+        public RenderableSelectionList(
+            IAnsiConsole console, string? title, int requestedPageSize,
+            List<T> choices, Func<T, string>? converter, Style? highlightStyle,
+            string? moreChoices)
             : base(console, requestedPageSize, choices, converter)
         {
             _console = console ?? throw new ArgumentNullException(nameof(console));
             _title = title;
             _highlightStyle = highlightStyle ?? new Style(foreground: Color.Blue);
+            _moreChoices = new Markup(moreChoices ?? MoreChoicesText);
         }
 
         protected override int CalculatePageSize(int requestedPageSize)
@@ -67,8 +73,9 @@ namespace Spectre.Console
 
             if (scrollable)
             {
+                // (Move up and down to reveal more choices)
                 list.Add(Text.Empty);
-                list.Add(new Markup("[grey](Move up and down to reveal more choices)[/]"));
+                list.Add(_moreChoices);
             }
 
             return new Rows(list);

src/Spectre.Console/Widgets/Prompt/SelectionPrompt.cs

@@ -38,6 +38,11 @@ namespace Spectre.Console
         /// </summary>
         public Style? HighlightStyle { get; set; }
 
+        /// <summary>
+        /// Gets or sets the text that will be displayed if there are more choices to show.
+        /// </summary>
+        public string? MoreChoicesText { get; set; }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="SelectionPrompt{T}"/> class.
         /// </summary>
@@ -64,8 +69,10 @@ namespace Spectre.Console
             }
 
             var converter = Converter ?? TypeConverterHelper.ConvertToString;
+            var list = new RenderableSelectionList<T>(
+                console, Title, PageSize, Choices,
+                converter, HighlightStyle, MoreChoicesText);
 
-            var list = new RenderableSelectionList<T>(console, Title, PageSize, Choices, converter, HighlightStyle);
             using (new RenderHookScope(console, list))
             {
                 console.Cursor.Hide();

src/Spectre.Console/Widgets/Prompt/SelectionPromptExtensions.cs

@@ -121,6 +121,24 @@ namespace Spectre.Console
             return obj;
         }
 
+        /// <summary>
+        /// Sets the text that will be displayed if there are more choices to show.
+        /// </summary>
+        /// <typeparam name="T">The prompt result type.</typeparam>
+        /// <param name="obj">The prompt.</param>
+        /// <param name="text">The text to display.</param>
+        /// <returns>The same instance so that multiple calls can be chained.</returns>
+        public static SelectionPrompt<T> MoreChoicesText<T>(this SelectionPrompt<T> obj, string? text)
+        {
+            if (obj is null)
+            {
+                throw new ArgumentNullException(nameof(obj));
+            }
+
+            obj.MoreChoicesText = text;
+            return obj;
+        }
+
         /// <summary>
         /// Sets the function to create a display string for a given choice.
         /// </summary>