Sync updates to system clock

Syncing with system clock looks nicer when the app is next to it.

Network Monitor/Monitors/BandwidthMonitor.cs

@@ -14,7 +14,7 @@ public abstract class BandwidthMonitor : Monitor
 
     protected abstract long GetTotalBytes();
 
-    protected BandwidthMonitor() : base(updateInterval: TimeSpan.FromSeconds(1))
+    protected BandwidthMonitor() : base(interval: TimeSpan.FromSeconds(1))
     {
     }
 

Network Monitor/Monitors/LatencyMonitor.cs

@@ -14,7 +14,7 @@ public class LatencyMonitor : Monitor
     private readonly string _host;
     private readonly int _timeout;
 
-    public LatencyMonitor(string host, TimeSpan timeout) : base(updateInterval: timeout)
+    public LatencyMonitor(string host, TimeSpan timeout) : base(interval: timeout)
     {
         Name = "Latency";
         Icon = '⟳';

Network Monitor/Monitors/Monitor.cs

@@ -7,19 +7,22 @@ namespace Network_Monitor.Monitors;
 
 public abstract class Monitor : ObservableObject
 {
-    private readonly DispatcherTimer _updateTimer;
+    private readonly SystemClockTimer _timer;
     private string _displayValue = string.Empty.PadRight(4);
 
-    protected Monitor(TimeSpan updateInterval)
+    protected Monitor(TimeSpan interval)
     {
-        if (updateInterval > TimeSpan.Zero)
+        var intervalSeconds = (int)interval.TotalSeconds;
+
+        if (intervalSeconds > 0)
         {
-            _updateTimer = new(DispatcherPriority.Normal)
+            _timer = new();
+            _timer.SecondChanged += async (_, _) =>
             {
-                Interval = updateInterval
+                if (string.IsNullOrWhiteSpace(DisplayValue) || DateTime.Now.Second % intervalSeconds == 0)
+                    await UpdateAsync();
             };
-            _updateTimer.Tick += async (_, _) => await UpdateAsync();
-            _updateTimer.Start();
+            _timer.Start();
         }
     }
 
@@ -38,6 +41,11 @@ protected Monitor(TimeSpan updateInterval)
     /// </summary>
     public Brush IconBrush { get; protected set; }
 
+    /// <summary>
+    /// Interval to update in seconds.
+    /// </summary>
+    public int IntervalSeconds { get; protected set; } = 5;
+
     /// <summary>
     /// User-friendly text to show in the UI.
     /// </summary>

Network Monitor/SystemClockTimer.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Threading;
+
+namespace Network_Monitor;
+
+/// <summary>
+/// A timer that is synced with the system clock.
+/// </summary>
+/// <remarks>
+/// <see href="https://github.com/danielchalmers/DesktopClock" />
+/// </remarks>
+public sealed class SystemClockTimer : IDisposable
+{
+    private readonly Timer _timer;
+
+    public SystemClockTimer()
+    {
+        _timer = new Timer(_ => OnTick());
+    }
+
+    /// <summary>
+    /// Occurs after the second of the system clock changes.
+    /// </summary>
+    public event EventHandler SecondChanged;
+
+    /// <summary>
+    /// Number of milliseconds until the next second on the system clock.
+    /// </summary>
+    private int MillisecondsUntilNextSecond => 1000 - DateTimeOffset.Now.Millisecond;
+
+    public void Dispose() => _timer.Dispose();
+
+    public void Start() => ScheduleTickForNextSecond();
+
+    public void Stop() => _timer.Change(Timeout.Infinite, Timeout.Infinite);
+
+    private void OnTick()
+    {
+        ScheduleTickForNextSecond();
+
+        SecondChanged?.Invoke(this, EventArgs.Empty);
+    }
+
+    /// <summary>
+    /// Starts the timer and schedules the tick for the next second on the system clock.
+    /// </summary>
+    private void ScheduleTickForNextSecond() =>
+        _timer.Change(MillisecondsUntilNextSecond, Timeout.Infinite);
+}