Enable preferences toolbar to style itself for Big Sur

Mac/AppAssets.swift

@@ -98,10 +98,6 @@ struct AppAssets {
 		return RSImage(named: "extensionPointTwitter")!
 	}()
 	
-	static var extensionPreference: RSImage? = {
-		return RSImage(contentsOfFile: "/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/KEXT.icns")
-	}()
-		
 	static var faviconTemplateImage: RSImage = {
 		return RSImage(named: "faviconTemplateImage")!
 	}()
@@ -146,6 +142,38 @@ struct AppAssets {
 		return NSImage(systemSymbolName: "safari", accessibilityDescription: nil)!
 	}()
 
+	static var preferencesToolbarAccountsImage: RSImage = {
+		if #available(macOS 10.16, *) {
+			return NSImage(systemSymbolName: "at", accessibilityDescription: nil)!
+		} else {
+			return NSImage(named: NSImage.userAccountsName)!
+		}
+	}()
+	
+	static var preferencesToolbarExtensionsImage: RSImage = {
+		if #available(macOS 10.16, *) {
+			return NSImage(named: "preferencesToolbarExtensions")!
+		} else {
+			return NSImage(contentsOfFile: "/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/KEXT.icns")!
+		}
+	}()
+	
+	static var preferencesToolbarGeneralImage: RSImage = {
+		if #available(macOS 10.16, *) {
+			return NSImage(systemSymbolName: "gearshape", accessibilityDescription: nil)!
+		} else {
+			return NSImage(named: NSImage.preferencesGeneralName)!
+		}
+	}()
+	
+	static var preferencesToolbarAdvancedImage: RSImage = {
+		if #available(macOS 10.16, *) {
+			return NSImage(systemSymbolName: "gearshape.2", accessibilityDescription: nil)!
+		} else {
+			return NSImage(named: NSImage.advancedName)!
+		}
+	}()
+
 	@available(macOS 10.16, *)
 	static var readClosedImage: RSImage = {
 		return NSImage(systemSymbolName: "largecircle.fill.circle", accessibilityDescription: nil)!

Mac/Preferences/PreferencesWindowController.swift

@@ -36,13 +36,13 @@ class PreferencesWindowController : NSWindowController, NSToolbarDelegate {
 		var specs = [PreferencesToolbarItemSpec]()
 		specs += [PreferencesToolbarItemSpec(identifierRawValue: ToolbarItemIdentifier.General,
 											 name: NSLocalizedString("General", comment: "Preferences"),
-											 image: NSImage(named: NSImage.preferencesGeneralName))]
+											 image: AppAssets.preferencesToolbarGeneralImage)]
 		specs += [PreferencesToolbarItemSpec(identifierRawValue: ToolbarItemIdentifier.Accounts,
 											 name: NSLocalizedString("Accounts", comment: "Preferences"),
-											 image: NSImage(named: NSImage.userAccountsName))]
+											 image: AppAssets.preferencesToolbarAccountsImage)]
 		specs += [PreferencesToolbarItemSpec(identifierRawValue: ToolbarItemIdentifier.Extensions,
 											 name: NSLocalizedString("Extensions", comment: "Preferences"),
-											 image: AppAssets.extensionPreference)]
+											 image: AppAssets.preferencesToolbarExtensionsImage)]
 
 		// Omit the Advanced Preferences for now because the Software Update related functionality is
 		// forbidden/non-applicable, and we can rely upon Apple to some extent for crash reports. We
@@ -51,7 +51,7 @@ class PreferencesWindowController : NSWindowController, NSToolbarDelegate {
 		#if !MAC_APP_STORE
 			specs += [PreferencesToolbarItemSpec(identifierRawValue: ToolbarItemIdentifier.Advanced,
 												 name: NSLocalizedString("Advanced", comment: "Preferences"),
-												 image: NSImage(named: NSImage.advancedName))]
+												 image: AppAssets.preferencesToolbarAdvancedImage)]
 		#endif
 		return specs
 	}()

Mac/Resources/Assets.xcassets/preferencesToolbarExtensions.imageset/Contents.json

@@ -0,0 +1,16 @@
+{
+  "images" : [
+    {
+      "filename" : "extensions.pdf",
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  },
+  "properties" : {
+    "preserves-vector-representation" : true,
+    "template-rendering-intent" : "template"
+  }
+}