Fixes #5349. Ignore non-readable poll events during ANSI shutdown

Terminal.Gui/Drivers/UnixHelpers/UnixIOHelper.cs

@@ -236,7 +236,20 @@ public static bool IsInputAvailable (Pollfd [] pollMap, int timeoutMs = 0)
         {
             int n = poll (pollMap, (uint)pollMap.Length, timeoutMs);
 
-            return n > 0;
+            if (n <= 0)
+            {
+                return false;
+            }
+
+            foreach (Pollfd pollfd in pollMap)
+            {
+                if ((pollfd.revents & (short)Condition.PollIn) != 0)
+                {
+                    return true;
+                }
+            }
+
+            return false;
         }
         catch
         {

Tests/UnitTestsParallelizable/Drivers/UnixIOHelperTests.cs

@@ -0,0 +1,85 @@
+using System.Runtime.InteropServices;
+using Terminal.Gui.Drivers;
+
+namespace DriverTests;
+
+/// <summary>
+///     Tests for <see cref="UnixIOHelper"/> polling semantics on Unix-like platforms.
+/// </summary>
+[Collection ("Driver Tests")]
+public class UnixIOHelperTests
+{
+    [DllImport ("libc", SetLastError = true)]
+    private static extern int pipe (int [] pipefd);
+
+    [DllImport ("libc", SetLastError = true)]
+    private static extern int close (int fd);
+
+    [Fact]
+    // Copilot
+    public void IsInputAvailable_ReturnsTrue_WhenPollReportsReadableData ()
+    {
+        if (!OperatingSystem.IsLinux () && !OperatingSystem.IsMacOS () && !OperatingSystem.IsFreeBSD ())
+        {
+            return;
+        }
+
+        int [] pipeFds = new int [2];
+        Assert.Equal (0, pipe (pipeFds));
+
+        try
+        {
+            byte [] payload = [0x41];
+            Assert.Equal (1, UnixIOHelper.write (pipeFds [1], payload, payload.Length));
+
+            UnixIOHelper.Pollfd [] pollMap =
+            [
+                new ()
+                {
+                    fd = pipeFds [0],
+                    events = (short)UnixIOHelper.Condition.PollIn
+                }
+            ];
+
+            Assert.True (UnixIOHelper.IsInputAvailable (pollMap, 0));
+        }
+        finally
+        {
+            close (pipeFds [0]);
+            close (pipeFds [1]);
+        }
+    }
+
+    [Fact]
+    // Copilot
+    public void IsInputAvailable_ReturnsFalse_WhenPollReportsNonReadableEvent ()
+    {
+        if (!OperatingSystem.IsLinux () && !OperatingSystem.IsMacOS () && !OperatingSystem.IsFreeBSD ())
+        {
+            return;
+        }
+
+        int [] pipeFds = new int [2];
+        Assert.Equal (0, pipe (pipeFds));
+
+        try
+        {
+            Assert.Equal (0, close (pipeFds [0]));
+
+            UnixIOHelper.Pollfd [] pollMap =
+            [
+                new ()
+                {
+                    fd = pipeFds [0],
+                    events = (short)UnixIOHelper.Condition.PollIn
+                }
+            ];
+
+            Assert.False (UnixIOHelper.IsInputAvailable (pollMap, 0));
+        }
+        finally
+        {
+            close (pipeFds [1]);
+        }
+    }
+}