improve:UI

Ink Canvas/Resources/Settings.cs

@@ -303,7 +303,7 @@ namespace Ink_Canvas
         [JsonProperty("isShowModeFingerToggleSwitch")]
         public bool IsShowModeFingerToggleSwitch { get; set; } = true;
         [JsonProperty("theme")]
-        public int Theme { get; set; }
+        public int Theme { get; set; } = 2;
 
         // 浮动栏按钮显示控制
         [JsonProperty("useLegacyFloatingBarUI")]

Ink Canvas/Windows/SettingsViews/SettingsWindow.xaml.cs

@@ -141,13 +141,27 @@ namespace Ink_Canvas.Windows.SettingsViews
                 {
                     0 => iNKORE.UI.WPF.Modern.ElementTheme.Light,
                     1 => iNKORE.UI.WPF.Modern.ElementTheme.Dark,
-                    _ => iNKORE.UI.WPF.Modern.ElementTheme.Default,
+                    _ => IsSystemThemeLight() ? iNKORE.UI.WPF.Modern.ElementTheme.Light : iNKORE.UI.WPF.Modern.ElementTheme.Dark,
                 };
                 iNKORE.UI.WPF.Modern.ThemeManager.SetRequestedTheme(this, elementTheme);
             }
             catch { }
         }
 
+        private static bool IsSystemThemeLight()
+        {
+            try
+            {
+                using (var themeKey = Microsoft.Win32.Registry.CurrentUser.OpenSubKey(
+                    @"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize"))
+                {
+                    if (themeKey?.GetValue("SystemUsesLightTheme") is int v) return v == 1;
+                }
+            }
+            catch { }
+            return false;
+        }
+
         #region 修复触摸屏鼠标指针消失问题
 
         [System.Runtime.InteropServices.DllImport("user32.dll")]