Add API to detect if the screen reader is active (#947)

Author: SteveL-MSFT

PSReadLine/Accessibility.cs

@@ -0,0 +1,23 @@
+/********************************************************************++
+Copyright (c) Microsoft Corporation.  All rights reserved.
+--********************************************************************/
+
+using System.Runtime.InteropServices;
+
+namespace Microsoft.PowerShell.Internal
+{
+    internal class Accessibility
+    {
+        internal static bool IsScreenReaderActive()
+        {
+            bool returnValue = false;
+
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                PlatformWindows.SystemParametersInfo(PlatformWindows.SPI_GETSCREENREADER, 0, ref returnValue, 0);
+            }
+
+            return returnValue;
+        }
+    }
+}

PSReadLine/PlatformWindows.cs

@@ -604,4 +604,10 @@ public override void BlankRestOfLine()
             SetCursorPosition(x, y);
         }
     }
+
+    internal const uint SPI_GETSCREENREADER = 0x0046;
+
+    [DllImport("user32.dll", SetLastError = true)]
+    [return: MarshalAs(UnmanagedType.Bool)]
+    internal static extern bool SystemParametersInfo(uint uiAction, uint uiParam, ref bool pvParam, uint fWinIni);
 }