protected void ImportSettingsFrom(DefaultHighlightingStrategy source)
		{
			if (source == null)
				throw new ArgumentNullException("source");
			properties = source.properties;
			extensions = source.extensions;
			digitColor = source.digitColor;
			defaultRuleSet = source.defaultRuleSet;
			name = source.name;
			rules = source.rules;
			environmentColors = source.environmentColors;
			defaultTextColor = source.defaultTextColor;
		}
		void UpdateSpanStateVariables()
		{
			inSpan = (currentSpanStack != null && !currentSpanStack.IsEmpty);
			activeSpan = inSpan ? currentSpanStack.Peek() : null;
			activeRuleSet = GetRuleSet(activeSpan);
		}
		protected virtual HighlightColor GetColor(HighlightRuleSet ruleSet, IDocument document, LineSegment currentSegment, int currentOffset, int currentLength)
		{
			if (ruleSet != null) {
				if (ruleSet.Reference != null) {
					return ruleSet.Highlighter.GetColor(document, currentSegment, currentOffset, currentLength);
				} else {
					return (HighlightColor)ruleSet.KeyWords[document,  currentSegment, currentOffset, currentLength];
				}
			}
			return null;
		}
		void ResolveRuleSetReferences()
		{
			foreach (HighlightRuleSet ruleSet in Rules) {
				if (ruleSet.Name == null) {
					defaultRuleSet = ruleSet;
				}
				
				foreach (Span aSpan in ruleSet.Spans) {
					if (aSpan.Rule != null) {
						bool found = false;
						foreach (HighlightRuleSet refSet in Rules) {
							if (refSet.Name == aSpan.Rule) {
								found = true;
								aSpan.RuleSet = refSet;
								break;
							}
						}
						if (!found) {
							aSpan.RuleSet = null;
							throw new HighlightingDefinitionInvalidException("The RuleSet " + aSpan.Rule + " could not be found in mode definition " + this.Name);
						}
					} else {
						aSpan.RuleSet = null;
					}
				}
			}
			
			if (defaultRuleSet == null) {
				throw new HighlightingDefinitionInvalidException("No default RuleSet is defined for mode definition " + this.Name);
			}
		}
		public void AddRuleSet(HighlightRuleSet aRuleSet)
		{
			HighlightRuleSet existing = FindHighlightRuleSet(aRuleSet.Name);
			if (existing != null) {
				existing.MergeFrom(aRuleSet);
			} else {
				rules.Add(aRuleSet);
			}
		}
		/// <summary>
		/// Merges spans etc. from the other rule set into this rule set.
		/// </summary>
		public void MergeFrom(HighlightRuleSet ruleSet)
		{
			for (int i = 0; i < delimiters.Length; i++) {
				delimiters[i] |= ruleSet.delimiters[i];
			}
			// insert merged spans in front of old spans
			ArrayList oldSpans = spans;
			spans = (ArrayList)ruleSet.spans.Clone();
			spans.AddRange(oldSpans);
			//keyWords.MergeFrom(ruleSet.keyWords);
			//prevMarkers.MergeFrom(ruleSet.prevMarkers);
			//nextMarkers.MergeFrom(ruleSet.nextMarkers);
		}