AvalonEdit: Fixed repainting issues when document was modified above the visible region (e.g. using split view) and the highlighting stack changed.

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/trunk@5584 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/CodeEditor.cs

@@ -7,23 +7,19 @@
 
 using System;
 using System.Collections.ObjectModel;
-using System.ComponentModel.Design;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Windows;
 using System.Windows.Controls;
-using System.Windows.Controls.Primitives;
 using System.Windows.Data;
 using System.Windows.Input;
-using System.Windows.Media;
 using System.Windows.Threading;
 
 using ICSharpCode.AvalonEdit.AddIn.Options;
 using ICSharpCode.AvalonEdit.Document;
 using ICSharpCode.AvalonEdit.Editing;
 using ICSharpCode.AvalonEdit.Highlighting;
-using ICSharpCode.AvalonEdit.Indentation;
 using ICSharpCode.AvalonEdit.Rendering;
 using ICSharpCode.Core;
 using ICSharpCode.Core.Presentation;
@@ -33,7 +29,6 @@ using ICSharpCode.SharpDevelop.Dom;
 using ICSharpCode.SharpDevelop.Editor;
 using ICSharpCode.SharpDevelop.Editor.AvalonEdit;
 using ICSharpCode.SharpDevelop.Editor.CodeCompletion;
-using ICSharpCode.SharpDevelop.Editor.Commands;
 
 namespace ICSharpCode.AvalonEdit.AddIn
 {

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

@@ -60,7 +60,6 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 		{
 			CheckIsHighlighting();
 			int number = line.LineNumber;
-			InvalidateHighlighting();
 			storedSpanStacks.RemoveAt(number);
 			isValid.RemoveAt(number);
 			if (number < isValid.Count) {

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

@@ -80,6 +80,7 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 		{
 			base.OnAddToTextView(textView);
 			textView.DocumentChanged += textView_DocumentChanged;
+			textView.VisualLineConstructionStarting += textView_VisualLineConstructionStarting;
 			OnDocumentChanged(textView);
 		}
 		
@@ -90,6 +91,19 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 			textView.Services.RemoveService(typeof(IHighlighter));
 			textView.Services.RemoveService(typeof(DocumentHighlighter));
 			textView.DocumentChanged -= textView_DocumentChanged;
+			textView.VisualLineConstructionStarting -= textView_VisualLineConstructionStarting;
+		}
+		
+		void textView_VisualLineConstructionStarting(object sender, VisualLineConstructionStartEventArgs e)
+		{
+			IHighlighter highlighter = ((TextView)sender).Services.GetService(typeof(IHighlighter)) as IHighlighter;
+			if (highlighter != null) {
+				// Force update of highlighting state up to the position where we start generating visual lines.
+				// This is necessary in case the document gets modified above the FirstLineInView so that the highlighting state changes.
+				// We need to detect this case and issue a redraw (through TextViewDocumentHighligher.OnHighlightStateChanged)
+				// before the visual line construction reuses existing lines that were built using the invalid highlighting state.
+				highlighter.GetSpanStack(e.FirstLineInView.LineNumber - 1);
+			}
 		}
 		
 		/// <inheritdoc/>
@@ -128,7 +142,7 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 		
 		sealed class TextViewDocumentHighlighter : DocumentHighlighter
 		{
-			TextView textView;
+			readonly TextView textView;
 			
 			public TextViewDocumentHighlighter(TextView textView, TextDocument document, HighlightingRuleSet baseRuleSet)
 				: base(document, baseRuleSet)
@@ -140,18 +154,58 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 			protected override void OnHighlightStateChanged(DocumentLine line, int lineNumber)
 			{
 				base.OnHighlightStateChanged(line, lineNumber);
-				int lineEndOffset = line.Offset + line.TotalLength;
-				if (lineEndOffset >= 0) {
-					// Do not use colorizer.CurrentContext - the colorizer might not be the only
-					// class calling DocumentHighlighter.HighlightLine, the the context might be null.
-					int length = this.Document.TextLength - lineEndOffset;
-					if (length != 0) {
-						// don't redraw if length == 0: at the end of the document, this would cause
-						// the last line which was already constructed to be redrawn ->
-						// we would get an exception due to disposing the line that was already constructed
-						textView.Redraw(lineEndOffset, length, DispatcherPriority.Normal);
-					}
+				if (textView.Document != this.Document) {
+					// May happen if document on text view was changed but some user code is still using the
+					// existing IHighlighter instance.
+					return;
 				}
+				
+				// The user may have inserted "/*" into the current line, and so far only that line got redrawn.
+				// So when the highlighting state is changed, we issue a redraw for the line immediately below.
+				// If the highlighting state change applies to the lines below, too, the construction of each line
+				// will invalidate the next line, and the construction pass will regenerate all lines.
+				
+				Debug.WriteLine("OnHighlightStateChanged forces redraw of line " + (lineNumber + 1));
+				
+				// If the VisualLine construction is in progress, we have to avoid sending redraw commands for
+				// anything above the line currently being constructed.
+				// It takes some explanation to see why this cannot happen.
+				// VisualLines always get constructed from top to bottom.
+				// Each VisualLine construction calls into the highlighter and thus forces an update of the
+				// highlighting state for all lines up to the one being constructed.
+				
+				// To guarantee that we don't redraw lines we just constructed, we need to show that when
+				// a VisualLine is being reused, the highlighting state at that location is still up-to-date.
+				
+				// This isn't exactly trivial and the initial implementation was incorrect in the presence of external document changes
+				// (e.g. split view).
+				
+				// For the first line in the view, the TextView.VisualLineConstructionStarting event is used to check that the
+				// highlighting state is up-to-date. If it isn't, this method will be executed, and it'll mark the first line
+				// in the view as requiring a redraw. This is safely possible because that event occurs before any lines are reused.
+				
+				// Once we take care of the first visual line, we won't get in trouble with other lines due to the top-to-bottom
+				// construction process.
+				
+				// 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
+				// until line N-1 (no change detected in VisualLineConstructionStarting event).
+				
+				// Induction step:
+				// If another line N+1 is being reused, then either
+				//     a) the previous line (the visual line containing document line N) was newly constructed
+				// or  b) the previous line was reused
+				// In case a, the construction updated the highlighting state. This means the stack at end of line N is up-to-date.
+				// In case b, the highlighting state at N-1 was up-to-date, and the text of line N was not changed.
+				//   (if the text was changed, the line could not have been reused).
+				// From this follows that the highlighting state at N is still up-to-date.
+				
+				// The above proof holds even in the presence of folding: folding only ever hides text in the middle of a visual line.
+				// The HighlightingColorizer will always be asked to highlight the LastDocumentLine of a visual line, so it will always
+				// invalidate the next visual line when a folded line is constructed and the highlighting stack changed.
+				
+				textView.Redraw(line.NextLine, DispatcherPriority.Normal);
 			}
 		}
 	}

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj

@@ -262,6 +262,7 @@
       <DependentUpon>TextView.cs</DependentUpon>
     </Compile>
     <Compile Include="Rendering\VisualLine.cs" />
+    <Compile Include="Rendering\VisualLineConstructionStartEventArgs.cs" />
     <Compile Include="Rendering\VisualLineElement.cs" />
     <Compile Include="Rendering\VisualLineElementGenerator.cs" />
     <Compile Include="Rendering\VisualLineElementTextRunProperties.cs">

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

@@ -398,18 +398,27 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		{
 			VerifyAccess();
 			bool removedLine = false;
+			bool changedSomethingBeforeOrInLine = false;
 			for (int i = 0; i < allVisualLines.Count; i++) {
 				VisualLine visualLine = allVisualLines[i];
 				int lineStart = visualLine.FirstDocumentLine.Offset;
 				int lineEnd = visualLine.LastDocumentLine.Offset + visualLine.LastDocumentLine.TotalLength;
-				if (!(lineEnd < offset || lineStart > offset + length)) {
-					removedLine = true;
-					allVisualLines.RemoveAt(i--);
-					DisposeVisualLine(visualLine);
+				if (offset <= lineEnd) {
+					changedSomethingBeforeOrInLine = true;
+					if (offset + length >= lineStart) {
+						removedLine = true;
+						allVisualLines.RemoveAt(i--);
+						DisposeVisualLine(visualLine);
+					}
 				}
 			}
 			if (removedLine) {
 				visibleVisualLines = null;
+			}
+			if (changedSomethingBeforeOrInLine) {
+				// Repaint not only when something in visible area was changed, but also when anything in front of it
+				// was changed. We might have to redraw the line number margin. Or the highlighting changed.
+				// However, we'll try to reuse the existing VisualLines.
 				InvalidateMeasure(redrawPriority);
 			}
 		}
@@ -571,13 +580,20 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		
 		/// <summary>
 		/// Gets whether the visual lines are valid.
-		/// Will return false after a call to Redraw(). Accessing the visual lines property
-		/// will force immediate regeneration of valid lines.
+		/// Will return false after a call to Redraw().
+		/// Accessing the visual lines property will cause a <see cref="VisualLinesInvalidException"/>
+		/// if this property is <c>false</c>.
 		/// </summary>
 		public bool VisualLinesValid {
 			get { return visibleVisualLines != null; }
 		}
 		
+		/// <summary>
+		/// Occurs when the TextView is about to be measured and will regenerate its visual lines.
+		/// This event may be used to mark visual lines as invalid that would otherwise be reused.
+		/// </summary>
+		public event EventHandler<VisualLineConstructionStartEventArgs> VisualLineConstructionStarting;
+		
 		/// <summary>
 		/// Occurs when the TextView was measured and changed its visual lines.
 		/// </summary>
@@ -695,6 +711,9 @@ namespace ICSharpCode.AvalonEdit.Rendering
 			
 			newVisualLines = new List<VisualLine>();
 			
+			if (VisualLineConstructionStarting != null)
+				VisualLineConstructionStarting(this, new VisualLineConstructionStartEventArgs(firstLineInView));
+			
 			var elementGeneratorsArray = elementGenerators.ToArray();
 			var lineTransformersArray = lineTransformers.ToArray();
 			var nextLine = firstLineInView;

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

@@ -0,0 +1,33 @@
+// <file>
+//     <copyright see="prj:///doc/copyright.txt"/>
+//     <license see="prj:///doc/license.txt"/>
+//     <author name="Daniel Grunwald"/>
+//     <version>$Revision$</version>
+// </file>
+
+using System;
+using ICSharpCode.AvalonEdit.Document;
+
+namespace ICSharpCode.AvalonEdit.Rendering
+{
+	/// <summary>
+	/// EventArgs for the <see cref="TextView.VisualLineConstructionStarting"/> event.
+	/// </summary>
+	public class VisualLineConstructionStartEventArgs : EventArgs
+	{
+		/// <summary>
+		/// Gets/Sets the first line that is visible in the TextView.
+		/// </summary>
+		public DocumentLine FirstLineInView { get; private set; }
+		
+		/// <summary>
+		/// Creates a new VisualLineConstructionStartEventArgs instance.
+		/// </summary>
+		public VisualLineConstructionStartEventArgs(DocumentLine firstLineInView)
+		{
+			if (firstLineInView == null)
+				throw new ArgumentNullException("firstLineInView");
+			this.FirstLineInView = firstLineInView;
+		}
+	}
+}