feat: support mac os

Package.swift

@@ -6,7 +6,8 @@ import PackageDescription
 let package = Package(
   name: "gitdiff",
   platforms: [
-    .iOS(.v15)
+    .iOS(.v15),
+    .macOS(.v13)
   ],
   products: [
     .library(

Sources/gitdiff/Core/PlatformColors.swift

@@ -0,0 +1,31 @@
+import SwiftUI
+
+#if os(iOS) || os(tvOS) || os(watchOS)
+  import UIKit
+#endif
+#if os(macOS)
+  import AppKit
+#endif
+
+/// Cross-platform system background color wrapper
+enum PlatformColors {
+  static var background: Color {
+    #if os(iOS) || os(tvOS) || os(watchOS)
+      return Color(UIColor.systemBackground)
+    #elseif os(macOS)
+      if #available(macOS 10.15, *) {
+        // There is no NSColor.systemBackground; windowBackgroundColor is closest for content areas
+        return Color(NSColor.windowBackgroundColor)
+      } else {
+        return Color.white
+      }
+    #else
+      return Color.white
+    #endif
+  }
+}
+
+extension Color {
+  /// A cross-platform background color similar to system background.
+  public static var appBackground: Color { PlatformColors.background }
+}

Sources/gitdiff/Views/DiffFileView.swift

@@ -110,5 +110,5 @@ struct DiffFileView: View {
 
   DiffFileView(file: sampleFile)
     .padding()
-    .background(Color(.systemBackground))
+    .background(Color.appBackground)
 }

Sources/gitdiff/Views/DiffLineView.swift

@@ -142,5 +142,5 @@ struct DiffLineView: View {
       )
     )
   }
-  .background(Color(.systemBackground))
+  .background(Color.appBackground)
 }

Sources/gitdiff/Views/DiffRenderer.swift

@@ -60,7 +60,7 @@ public struct DiffRenderer: View {
         .padding()
       }
     }
-    .background(Color(.systemBackground))
+    .background(Color.appBackground)
   }
 }
 
@@ -103,7 +103,7 @@ public struct DiffRenderer: View {
 
   // With dark theme
   DiffRenderer(diffText: text)
-    .diffTheme(.vsCodeDark)
+    .diffTheme(.dark)
 
   // With custom configuration
   DiffRenderer(diffText: text)