AvalonEdit: Fixed issue that caused the collapsed line state in the HeightTree to become inconsistent with the state in the folding manager.

This bug was causing strange scrolling behavior when a file with collapsed folding sections got reloaded due to external changes.

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingManager.cs

@@ -68,13 +68,16 @@ namespace ICSharpCode.AvalonEdit.Folding
 		void OnDocumentChanged(DocumentChangeEventArgs e)
 		{
 			foldings.UpdateOffsets(e);
-			FoldingSection s = foldings.FindFirstSegmentWithStartAfter(e.Offset);
-			while (s != null && s.StartOffset == e.Offset) {
-				FoldingSection next = foldings.GetNextSegment(s);
-				if (s.Length == 0) {
-					RemoveFolding(s);
+			int newEndOffset = e.Offset + e.InsertionLength;
+			// extend end offset to the end of the line (including delimiter)
+			var endLine = document.GetLineByOffset(newEndOffset);
+			newEndOffset = endLine.Offset + endLine.TotalLength;
+			foreach (var affectedFolding in foldings.FindOverlappingSegments(e.Offset, newEndOffset - e.Offset)) {
+				if (affectedFolding.Length == 0) {
+					RemoveFolding(affectedFolding);
+				} else {
+					affectedFolding.ValidateCollapsedLineSections();
 				}
-				s = next;
 			}
 		}
 		#endregion
@@ -100,7 +103,7 @@ namespace ICSharpCode.AvalonEdit.Folding
 				throw new ArgumentException();
 			foreach (FoldingSection fs in foldings) {
 				if (fs.collapsedSections != null) {
-					CollapsedLineSection[] c = new CollapsedLineSection[textViews.Count];
+					var c = new CollapsedLineSection[textViews.Count];
 					Array.Copy(fs.collapsedSections, 0, c, 0, pos);
 					Array.Copy(fs.collapsedSections, pos + 1, c, pos, c.Length - pos);
 					fs.collapsedSections = c;
@@ -108,15 +111,6 @@ namespace ICSharpCode.AvalonEdit.Folding
 			}
 		}
 		
-		internal CollapsedLineSection[] CollapseLines(DocumentLine start, DocumentLine end)
-		{
-			CollapsedLineSection[] c = new CollapsedLineSection[textViews.Count];
-			for (int i = 0; i < c.Length; i++) {
-				c[i] = textViews[i].CollapseLines(start, end);
-			}
-			return c;
-		}
-		
 		internal void Redraw()
 		{
 			foreach (TextView textView in textViews)

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingSection.cs

@@ -2,6 +2,7 @@
 // This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
 
 using System;
+using System.Diagnostics;
 using System.Text;
 using System.Windows.Threading;
 using ICSharpCode.AvalonEdit.Document;
@@ -28,15 +29,20 @@ namespace ICSharpCode.AvalonEdit.Folding
 				if (isFolded != value) {
 					isFolded = value;
 					if (value) {
+						// Create collapsed sections
 						if (manager != null) {
 							DocumentLine startLine = manager.document.GetLineByOffset(StartOffset);
 							DocumentLine endLine = manager.document.GetLineByOffset(EndOffset);
 							if (startLine != endLine) {
 								DocumentLine startLinePlusOne = startLine.NextLine;
-								collapsedSections = manager.CollapseLines(startLinePlusOne, endLine);
+								collapsedSections = new CollapsedLineSection[manager.textViews.Count];
+								for (int i = 0; i < collapsedSections.Length; i++) {
+									collapsedSections[i] = manager.textViews[i].CollapseLines(startLinePlusOne, endLine);
+								}
 							}
 						}
 					} else {
+						// Destroy collapsed sections
 						RemoveCollapsedLineSection();
 					}
 					if (manager != null)
@@ -45,6 +51,9 @@ namespace ICSharpCode.AvalonEdit.Folding
 			}
 		}
 		
+		/// <summary>
+		/// Creates new collapsed section when a text view is added to the folding manager.
+		/// </summary>
 		internal CollapsedLineSection CollapseSection(TextView textView)
 		{
 			DocumentLine startLine = manager.document.GetLineByOffset(StartOffset);
@@ -56,6 +65,30 @@ namespace ICSharpCode.AvalonEdit.Folding
 			return null;
 		}
 		
+		internal void ValidateCollapsedLineSections()
+		{
+			DocumentLine startLine = manager.document.GetLineByOffset(StartOffset);
+			DocumentLine endLine = manager.document.GetLineByOffset(EndOffset);
+			if (startLine == endLine) {
+				RemoveCollapsedLineSection();
+			} else {
+				if (collapsedSections == null)
+					collapsedSections = new CollapsedLineSection[manager.textViews.Count];
+				// Validate collapsed line sections
+				DocumentLine startLinePlusOne = startLine.NextLine;
+				for (int i = 0; i < collapsedSections.Length; i++) {
+					var collapsedSection = collapsedSections[i];
+					if (collapsedSection == null || collapsedSection.Start != startLinePlusOne || collapsedSection.End != endLine) {
+						// recreate this collapsed section
+						Debug.WriteLine("CollapsedLineSection validation - recreate collapsed section from " + startLinePlusOne + " to " + endLine);
+						if (collapsedSection != null)
+							collapsedSection.Uncollapse();
+						collapsedSections[i] = manager.textViews[i].CollapseLines(startLinePlusOne, endLine);
+					}
+				}
+			}
+		}
+		
 		/// <summary>
 		/// Gets/Sets the text used to display the collapsed version of the folding section.
 		/// </summary>

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Rendering/CollapsedLineSection.cs

@@ -11,7 +11,7 @@ namespace ICSharpCode.AvalonEdit.Rendering
 	/// Represents a collapsed line section.
 	/// Use the Uncollapse() method to uncollapse the section.
 	/// </summary>
-	public sealed class CollapsedLineSection : INotifyPropertyChanged
+	public sealed class CollapsedLineSection
 	{
 		bool isCollapsed = true;
 		DocumentLine start, end;
@@ -41,7 +41,7 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		/// This property initially is true and turns to false when uncollapsing the section.
 		/// </summary>
 		public bool IsCollapsed {
-			get { return isCollapsed; }
+			get { return start != null; }
 		}
 		
 		/// <summary>
@@ -51,10 +51,7 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		/// </summary>
 		public DocumentLine Start {
 			get { return start; }
-			internal set {
-				start = value;
-				// TODO: raised property changed event (but only after the operation is complete)
-			}
+			internal set { start = value; }
 		}
 		
 		/// <summary>
@@ -64,46 +61,26 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		/// </summary>
 		public DocumentLine End {
 			get { return end; }
-			internal set {
-				end = value;
-				// TODO: raised property changed event (but only after the operation is complete)
-			}
+			internal set { end = value; }
 		}
 		
 		/// <summary>
 		/// Uncollapses the section.
 		/// This causes the Start and End properties to be set to null!
-		/// Runtime: O(log(n))
+		/// Does nothing if the section is already uncollapsed.
 		/// </summary>
-		/// <exception cref="InvalidOperationException">
-		/// The section is already uncollapsed, or the text containing the section was deleted.
-		/// </exception>
 		public void Uncollapse()
 		{
 			if (start == null)
-				throw new InvalidOperationException();
+				return;
 			
 			heightTree.Uncollapse(this);
 			#if DEBUG
 			heightTree.CheckProperties();
 			#endif
 			
-			start = end = null;
-			isCollapsed = false;
-			NotifyPropertyChanged("Start");
-			NotifyPropertyChanged("End");
-			NotifyPropertyChanged("IsCollapsed");
-		}
-		
-		/// <summary>
-		/// Is raised when of the properties Start,End,IsCollapsed changes.
-		/// </summary>
-		public event PropertyChangedEventHandler PropertyChanged;
-		
-		void NotifyPropertyChanged(string propertyName)
-		{
-			if (PropertyChanged != null)
-				PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
+			start = null;
+			end = null;
 		}
 		
 		/// <summary>
@@ -113,7 +90,7 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		public override string ToString()
 		{
 			return "[CollapsedSection" + ID + " Start=" + (start != null ? start.LineNumber.ToString() : "null")
-				+ " End=" + (end != null ? end.LineNumber.ToString() : "null") + " IsCollapsed=" + isCollapsed + "]";
+				+ " End=" + (end != null ? end.LineNumber.ToString() : "null") + "]";
 		}
 	}
 }

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Rendering/TextView.cs

@@ -999,12 +999,18 @@ namespace ICSharpCode.AvalonEdit.Rendering
 			
 			visualLine.ConstructVisualElements(textSource, elementGeneratorsArray);
 			
-			#if DEBUG
-			for (int i = visualLine.FirstDocumentLine.LineNumber + 1; i <= visualLine.LastDocumentLine.LineNumber; i++) {
-				if (!heightTree.GetIsCollapsed(i))
-					throw new InvalidOperationException("Line " + i + " was skipped by a VisualLineElementGenerator, but it is not collapsed.");
+			if (visualLine.FirstDocumentLine != visualLine.LastDocumentLine) {
+				// Check whether the lines are collapsed correctly:
+				double firstLinePos = heightTree.GetVisualPosition(visualLine.FirstDocumentLine.NextLine);
+				double lastLinePos = heightTree.GetVisualPosition(visualLine.LastDocumentLine);
+				if (!firstLinePos.IsClose(lastLinePos)) {
+					for (int i = visualLine.FirstDocumentLine.LineNumber + 1; i <= visualLine.LastDocumentLine.LineNumber; i++) {
+						if (!heightTree.GetIsCollapsed(i))
+							throw new InvalidOperationException("Line " + i + " was skipped by a VisualLineElementGenerator, but it is not collapsed.");
+					}
+					throw new InvalidOperationException("All lines collapsed but visual pos different - height tree inconsistency?");
+				}
 			}
-			#endif
 			
 			visualLine.RunTransformers(textSource, lineTransformersArray);