simplify class and add tests

DesktopClock.Tests/PixelShifterTests.cs

@@ -0,0 +1,55 @@
+using System;
+using DesktopClock.Utilities;
+
+namespace DesktopClock.Tests;
+
+public class PixelShifterTests
+{
+    [Theory]
+    [InlineData(5, 10)] // Evenly divisible.
+    [InlineData(3, 10)] // Not evenly divisible.
+    [InlineData(10, 5)] // Amount is larger than total.
+    public void ShiftX_ShouldNotExceedMaxTotalShift(int shiftAmount, int maxTotalShift)
+    {
+        var shifter = new PixelShifter
+        {
+            ShiftAmount = shiftAmount,
+            MaxTotalShift = maxTotalShift,
+        };
+
+        double totalShiftX = 0;
+
+        // Test 100 times because it's random.
+        for (var i = 0; i < 100; i++)
+        {
+            var shift = shifter.ShiftX();
+            totalShiftX += shift;
+
+            Assert.InRange(Math.Abs(totalShiftX), 0, maxTotalShift);
+        }
+    }
+
+    [Theory]
+    [InlineData(5, 10)] // Evenly divisible.
+    [InlineData(3, 10)] // Not evenly divisible.
+    [InlineData(10, 5)] // Amount is larger than total.
+    public void ShiftY_ShouldNotExceedMaxTotalShift(int shiftAmount, int maxTotalShift)
+    {
+        var shifter = new PixelShifter
+        {
+            ShiftAmount = shiftAmount,
+            MaxTotalShift = maxTotalShift,
+        };
+
+        double totalShiftY = 0;
+
+        // Test 100 times because it's random.
+        for (var i = 0; i < 100; i++)
+        {
+            var shift = shifter.ShiftY();
+            totalShiftY += shift;
+
+            Assert.InRange(Math.Abs(totalShiftY), 0, maxTotalShift);
+        }
+    }
+}

DesktopClock/MainWindow.xaml.cs

@@ -214,8 +214,12 @@ private void SystemClockTimer_SecondChanged(object sender, EventArgs e)
 
         if (Settings.Default.BurnInMitigation)
         {
-            _pixelShifter ??= new(this);
-            Dispatcher.Invoke(_pixelShifter.ShiftWindow);
+            _pixelShifter ??= new();
+            Dispatcher.Invoke(() =>
+            {
+                Left += _pixelShifter.ShiftX();
+                Top += _pixelShifter.ShiftY();
+            });
         }
     }
 

DesktopClock/Utilities/PixelShifter.cs

@@ -1,12 +1,10 @@
 using System;
-using System.Windows;
 
 namespace DesktopClock.Utilities;
 
 public class PixelShifter
 {
     private readonly Random _random = new();
-    private readonly Window _window;
     private double _totalShiftX;
     private double _totalShiftY;
 
@@ -20,34 +18,31 @@ public class PixelShifter
     /// </summary>
     public int MaxTotalShift { get; set; } = 4;
 
-    public PixelShifter(Window window)
+    public double ShiftX()
     {
-        _window = window;
-    }
+        var shift = _random.Next(-ShiftAmount, ShiftAmount + 1);
+        var newTotalShiftX = _totalShiftX + shift;
 
-    /// <summary>
-    /// Shifts the location of the window randomly to help prevent screen burn-in.
-    /// </summary>
-    public void ShiftWindow()
-    {
-        double CalculateShift(ref double totalShift)
+        if (Math.Abs(newTotalShiftX) <= MaxTotalShift)
         {
-            var shift = _random.Next(-ShiftAmount, ShiftAmount + 1);
-            var newTotalShift = totalShift + shift;
+            _totalShiftX = newTotalShiftX;
+            return shift;
+        }
 
-            if (Math.Abs(newTotalShift) <= MaxTotalShift)
-            {
-                totalShift = newTotalShift;
-                return shift;
-            }
+        return 0;
+    }
 
-            return 0;
-        }
+    public double ShiftY()
+    {
+        var shift = _random.Next(-ShiftAmount, ShiftAmount + 1);
+        var newTotalShiftY = _totalShiftY + shift;
 
-        var shiftX = CalculateShift(ref _totalShiftX);
-        var shiftY = CalculateShift(ref _totalShiftY);
+        if (Math.Abs(newTotalShiftY) <= MaxTotalShift)
+        {
+            _totalShiftY = newTotalShiftY;
+            return shift;
+        }
 
-        _window.Left += shiftX;
-        _window.Top += shiftY;
+        return 0;
     }
 }