Add support for obsolete CSS2 colors

System colors that were part of the CSS2 spec, but have since been removed. However, they show up when pasting text from Microsoft software like Word into Quill on web.

Author: MichaelMarner

lib/src/common/utils/web_colors.dart

@@ -2,6 +2,7 @@
 // https://github.com/vincevargadev/kolors_flutter
 
 import 'dart:ui';
+import 'package:flutter/foundation.dart';
 
 /// All the named web colors.
 class WebColors {
@@ -146,6 +147,7 @@ class WebColors {
   static const slateGray = Color(0xFF708090);
   static const darkSlateGray = Color(0xFF2F4F4F);
   static const black = Color(0xFF000000);
+  static const transparent = Color(0);
 
   static const values = [
     indianRed,
@@ -437,5 +439,40 @@ class WebColors {
     'slategray': slateGray,
     'darkslategray': darkSlateGray,
     'black': black,
+
+    // the follow colors were part of the CSS2 standard, but have since been removed.
+    // however these names tend to show up when copy/pasting from Microsoft products
+    // into Quill on web. W3C recommends using a default color for these.
+    //
+    // For more info, see here
+    // http://w3.org/TR/CSS2/ui.html#system-colors
+    'activeborder': black,
+    'activecaption': black,
+    'appworkspace': transparent,
+    'background': transparent,
+    'buttonface': transparent,
+    'buttonhighlight': transparent,
+    'buttonshadow': transparent,
+    'buttontext': black,
+    'captiontext': black,
+    'graytext': gray,
+    'highlight': gray,
+    'highlighttext': black,
+    'inactiveborder': black,
+    'inactivecaption': black,
+    'inactivecaptiontext': black,
+    'infobackground': transparent,
+    'infotext': black,
+    'menu': transparent,
+    'menutext': black,
+    'scrollbar': transparent,
+    'threeddarkshadow': transparent,
+    'threedface': transparent,
+    'threedhighlight': transparent,
+    'threedlightshadow': transparent,
+    'threedshadow': transparent,
+    'window': transparent,
+    'windowframe': black,
+    'windowtext': black,
   };
 }

test/common/utils/color_test.dart

@@ -14,6 +14,10 @@ void main() {
       expect(stringToColor('lightgoldenrodyellow').toARGB32(), 0xFFFAFAD2);
       expect(stringToColor('LIGHTGOLDENRODYELLOW').toARGB32(), 0xFFFAFAD2);
     });
+    test('Obsolete CSS2 color names pasted from word resolve to a value', () {
+      // test some web colors to make sure they resolve correctly
+      expect(stringToColor('windowtext').toARGB32(), 0xff000000);
+    });
     test('Can resolve transparent', () {
       // test some web colors to make sure they resolve correctly
       expect(stringToColor('transparent').toARGB32(), 0);