Add ScreenReader support CLI option

That should default to enabled when one is detected on startup,
but also allows the support to be forcibly enabled.

Author: andyleejordan

PSReadLine/Accessibility.cs

@@ -14,8 +14,9 @@ internal static bool IsScreenReaderActive()
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
             {
+                // NOTE: This API can detect if a third-party screen reader is active, such as NVDA, but not the in-box Windows Narrator.
                 PlatformWindows.SystemParametersInfo(PlatformWindows.SPI_GETSCREENREADER, 0, ref returnValue, 0);
-            }
+            } // TODO: Support other platforms per https://code.visualstudio.com/docs/configure/accessibility/accessibility
 
             return returnValue;
         }

PSReadLine/Cmdlets.cs

@@ -15,6 +15,7 @@
 using System.Runtime.InteropServices;
 using System.Threading;
 using Microsoft.PowerShell.PSReadLine;
+using Microsoft.PowerShell.Internal;
 using AllowNull = System.Management.Automation.AllowNullAttribute;
 
 namespace Microsoft.PowerShell
@@ -163,6 +164,11 @@ public class PSConsoleReadLineOptions
         /// </summary>
         public const int DefaultAnsiEscapeTimeout = 100;
 
+        /// <summary>
+        /// If screen reader support is enabled, which enables safe rendering using ANSI control codes.
+        /// </summary>
+        public static readonly bool DefaultScreenReader = Accessibility.IsScreenReaderActive();
+
         static PSConsoleReadLineOptions()
         {
             // For inline-view suggestion text, we use the new FG color 'dim white italic' when possible, because it provides
@@ -224,6 +230,7 @@ public PSConsoleReadLineOptions(string hostName, bool usingLegacyConsole)
                     : PredictionSource.HistoryAndPlugin;
             PredictionViewStyle = DefaultPredictionViewStyle;
             MaximumHistoryCount = 0;
+            ScreenReader = DefaultScreenReader;
 
             var historyFileName = hostName + "_history.txt";
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
@@ -533,6 +540,8 @@ public object ListPredictionTooltipColor
 
         public bool TerminateOrphanedConsoleApps { get; set; }
 
+        public bool ScreenReader { get; set; }
+
         internal string _defaultTokenColor;
         internal string _commentColor;
         internal string _keywordColor;
@@ -847,6 +856,14 @@ public SwitchParameter TerminateOrphanedConsoleApps
         }
         internal SwitchParameter? _terminateOrphanedConsoleApps;
 
+        [Parameter]
+        public SwitchParameter ScreenReader
+        {
+            get => _screenReader.GetValueOrDefault();
+            set => _screenReader = value;
+        }
+        internal SwitchParameter? _screenReader;
+
         [ExcludeFromCodeCoverage]
         protected override void EndProcessing()
         {

PSReadLine/Options.cs

@@ -185,6 +185,10 @@ private void SetOptionsInternal(SetPSReadLineOption options)
                             nameof(Options.TerminateOrphanedConsoleApps)));
                 }
             }
+            if (options._screenReader.HasValue)
+            {
+                Options.ScreenReader = options.ScreenReader;
+            }
         }
 
         private void SetKeyHandlerInternal(string[] keys, Action<ConsoleKeyInfo?, object> handler, string briefDescription, string longDescription, ScriptBlock scriptBlock)