Fixed ArgumentException in TextView.Redraw when deleting line in XML document.

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/trunk@5766 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/DocumentHighlighter.cs

@@ -179,7 +179,7 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 			//Debug.WriteLine("Highlight line " + lineNumber + (highlightedLine != null ? "" : " (span stack only)"));
 			spanStack = storedSpanStacks[lineNumber - 1];
 			HighlightLineInternal(line);
-			if (storedSpanStacks[lineNumber] != spanStack) {
+			if (!EqualSpanStacks(spanStack, storedSpanStacks[lineNumber])) {
 				isValid[lineNumber] = true;
 				//Debug.WriteLine("Span stack in line " + lineNumber + " changed from " + storedSpanStacks[lineNumber] + " to " + spanStack);
 				storedSpanStacks[lineNumber] = spanStack;
@@ -198,6 +198,25 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 			}
 		}
 		
+		static bool EqualSpanStacks(SpanStack a, SpanStack b)
+		{
+			// We must use value equality between the stacks because TextViewDocumentHighlighter.OnHighlightStateChanged
+			// depends on the fact that equal input state + unchanged line contents produce equal output state.
+			if (a == b)
+				return true;
+			if (a == null || b == null)
+				return false;
+			while (!a.IsEmpty && !b.IsEmpty) {
+				if (a.Peek() != b.Peek())
+					return false;
+				a = a.Pop();
+				b = b.Pop();
+				if (a == b)
+					return true;
+			}
+			return a.IsEmpty && b.IsEmpty;
+		}
+		
 		/// <summary>
 		/// Is called when the highlighting state at the end of the specified line has changed.
 		/// </summary>

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingColorizer.cs

@@ -218,7 +218,7 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 				
 				// We'll prove that: if line N is being reused, then the highlighting state is up-to-date until (end of) line N-1.
 				
-				// Start of induction: the first line in view can is reused only if the highlighting state was up-to-date
+				// Start of induction: the first line in view is reused only if the highlighting state was up-to-date
 				// until line N-1 (no change detected in VisualLineConstructionStarting event).
 				
 				// Induction step: