Refactor: move CopyStyle to ThemeHelper class

Moved the CopyStyle method from Theme to a new static ThemeHelper class for better code organization and reusability. Updated all references in Theme to use ThemeHelper.CopyStyle. Added ThemeHelper.cs and necessary using directives.

Author: Jack251970

Flow.Launcher.Core/Resource/Theme.cs

@@ -798,7 +798,7 @@ private void ApplyPreviewBackground(Color? bgColor = null)
                 Application.Current.Resources["WindowBorderStyle"] is Style originalStyle)
             {
                 // Copy the original style, including the base style if it exists
-                CopyStyle(originalStyle, previewStyle);
+                ThemeHelper.CopyStyle(originalStyle, previewStyle);
             }
 
             // Apply background color (remove transparency in color)
@@ -817,21 +817,6 @@ private void ApplyPreviewBackground(Color? bgColor = null)
             Application.Current.Resources["PreviewWindowBorderStyle"] = previewStyle;
         }
 
-        private void CopyStyle(Style originalStyle, Style targetStyle)
-        {
-            // If the style is based on another style, copy the base style first
-            if (originalStyle.BasedOn != null)
-            {
-                CopyStyle(originalStyle.BasedOn, targetStyle);
-            }
-
-            // Copy the setters from the original style
-            foreach (var setter in originalStyle.Setters.OfType<Setter>())
-            {
-                targetStyle.Setters.Add(new Setter(setter.Property, setter.Value));
-            }
-        }
-
         private void ColorizeWindow(string theme, BackdropTypes backdropType)
         {
             var dict = GetThemeResourceDictionary(theme);

Flow.Launcher.Core/Resource/ThemeHelper.cs

@@ -1,9 +1,26 @@
-using System.Windows.Media;
+using System.Linq;
+using System.Windows;
+using System.Windows.Media;
 
 namespace Flow.Launcher.Core.Resource;
 
 public static class ThemeHelper
 {
+    public static void CopyStyle(Style originalStyle, Style targetStyle)
+    {
+        // If the style is based on another style, copy the base style first
+        if (originalStyle.BasedOn != null)
+        {
+            CopyStyle(originalStyle.BasedOn, targetStyle);
+        }
+
+        // Copy the setters from the original style
+        foreach (var setter in originalStyle.Setters.OfType<Setter>())
+        {
+            targetStyle.Setters.Add(new Setter(setter.Property, setter.Value));
+        }
+    }
+
     public static SolidColorBrush GetFreezeSolidColorBrush(Color color)
     {
         var brush = new SolidColorBrush(color);