From a40e90f06e45ecd2c29e7291204474fc9b577124 Mon Sep 17 00:00:00 2001
From: Tig <tig@users.noreply.github.com>
Date: Tue, 21 Oct 2025 01:49:58 -0600
Subject: [PATCH] Refactor Scrolling.cs for timer management and nullability

Enabled nullable reference types with `#nullable enable` for improved safety. Replaced the `pulsing` flag with a new `_progressTimer` object to better manage the progress bar's timer lifecycle. Updated `AppOnInitialized` and `AppUnloaded` methods to handle timer initialization and cleanup properly, preventing potential memory leaks.

Simplified code by removing unnecessary comments and aligning method signatures with nullable reference type annotations.
---
 Examples/UICatalog/Scenarios/Scrolling.cs | 32 ++++++++++++-----------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/Examples/UICatalog/Scenarios/Scrolling.cs b/Examples/UICatalog/Scenarios/Scrolling.cs
index 6b14d755b..43776fa83 100644
--- a/Examples/UICatalog/Scenarios/Scrolling.cs
+++ b/Examples/UICatalog/Scenarios/Scrolling.cs
@@ -1,4 +1,6 @@
-namespace UICatalog.Scenarios;
+#nullable enable
+
+namespace UICatalog.Scenarios;
 
 [ScenarioMetadata ("Scrolling", "Content scrolling, IScrollBars, etc...")]
 [ScenarioCategory ("Controls")]
@@ -6,6 +8,8 @@
 [ScenarioCategory ("Tests")]
 public class Scrolling : Scenario
 {
+    private static object? _progressTimer = null;
+
     public override void Main ()
     {
         Application.Init ();
@@ -38,10 +42,6 @@ public class Scrolling : Scenario
 
         app.Add (demoView);
 
-        //// NOTE: This call to EnableScrollBar is technically not needed because the reference
-        //// NOTE: to demoView.HorizontalScrollBar below will cause it to be lazy created.
-        //// NOTE: The call included in this sample to for illustration purposes.
-        //demoView.EnableScrollBar (Orientation.Horizontal);
         var hCheckBox = new CheckBox
         {
             X = Pos.X (demoView),
@@ -52,10 +52,6 @@ public class Scrolling : Scenario
         app.Add (hCheckBox);
         hCheckBox.CheckedStateChanged += (sender, args) => { demoView.HorizontalScrollBar.Visible = args.Value == CheckState.Checked; };
 
-        //// NOTE: This call to EnableScrollBar is technically not needed because the reference
-        //// NOTE: to demoView.HorizontalScrollBar below will cause it to be lazy created.
-        //// NOTE: The call included in this sample to for illustration purposes.
-        //demoView.EnableScrollBar (Orientation.Vertical);
         var vCheckBox = new CheckBox
         {
             X = Pos.Right (hCheckBox) + 3,
@@ -96,8 +92,6 @@ public class Scrolling : Scenario
 
         app.Add (progress);
 
-        var pulsing = true;
-
         app.Initialized += AppOnInitialized;
         app.Unloaded += AppUnloaded;
 
@@ -108,17 +102,25 @@ public class Scrolling : Scenario
 
         return;
 
-        void AppOnInitialized (object sender, EventArgs e)
+        void AppOnInitialized (object? sender, EventArgs e)
         {
             bool TimerFn ()
             {
                 progress.Pulse ();
 
-                return pulsing;
+                return _progressTimer is { };
             }
 
-            Application.AddTimeout (TimeSpan.FromMilliseconds (200), TimerFn);
+            _progressTimer = Application.AddTimeout (TimeSpan.FromMilliseconds (200), TimerFn);
+        }
+
+        void AppUnloaded (object? sender, EventArgs args)
+        {
+            if (_progressTimer is { })
+            {
+                Application.RemoveTimeout (_progressTimer);
+                _progressTimer = null;
+            }
         }
-        void AppUnloaded (object sender, EventArgs args) { pulsing = false; }
     }
 }
\ No newline at end of file