Word Wrap for Text Viewer and Editor

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Project is part of Google_Summer_of_Code_2006

Student: Ahti Kitsik (ahti.kitsik@gmail.com)

Blog: http://ahtik.com/blog/

Mentor: Philippe Ombredanne

First "micro/alpha"-release is available at http://ahtik.com/blog/2006/06/18/first-alpha-of-eclipse-word-wrap-released/


Implementation notes -- developer-only reference

Related interfaces and classes


Interface to a text editor. This interface defines functional extensions to IEditorPart as well as the configuration capabilities of a text editor.

Text editors are configured with an IDocumentProvider which delivers a textual presentation (IDocument) of the editor's input. The editor works on the document and forwards all input element related calls, such as save, to the document provider. The provider also delivers the input's annotation model which is used to control the editor's vertical ruler.


Represents text providing support for

  • text manipulation,
  • positions,
  • partitions,
  • line information,
  • document change listeners,
  • document partition change listeners


A IDocumentInformationMapping represents a mapping between the coordinates of two IDocument objects: the original and the image. The document information mapping can translate document information such as line numbers or character ranges given for the original into the corresponding information of the image and vice versa.


Storing and managing text.


Maps character positions to line numbers and vice versa.


Adapts an org.eclipse.jface.text.IDocument to the org.eclipse.swt.custom.StyledTextContent interface. The document adapter is used by org.eclipse.jface.text.TextViewer to translate document changes into styled text content changes and vice versa.

Currently there seems to be two candidates for managing and providing wrapping services:

  • IDocumentAdapter and
  • IDocumentInformationMapping.

Patching strategy

Two possible locations:

  • Patching StyledText - this would become too bloated for keeping wrapped document model. In addition, as some visuals need wrapped and some need unwrapped document model then this would separate StyledText wrapped text from IDocument/TextViewer too much. Currently StyledText has WRAP support but it's not complete!
  • Patching TextViewer - this means patching one or several of it's accessories like IDocumentAdapter, IDocumentInformationMapping. This way column rulers and viewer widget would have access to wrapped or unwrapped model, whichever is more appropriate in that context. Most of the time wrapped model can be used.

Both of these strategies require modifying at least LineNumberRulerColumn.

Experimenting with IDocumentAdapter showed that wrapping works but there seems to be no way to introduce wrapped document to the column rulers without modifying underlying file.

IDocumentInformationMapping might be a better place for wrapping model but as current implementation is pretty complex (as is probably the whole code folding support) then I would love to get some hints about the feasibility of extending this with word wrap.

Experiment with IDocumentAdapter

Creating IDocumentAdapter that supports word wrap would fix TextViewer to support wrapping. But as wrapping is only visual then all related ruler columns like annotations, line numberings etc fall apart.

Current AbstractDocumentAdapter wordwrap patch is providing visually wrapping viewer without any externally accessible wrapping model.

In addition JFaceTextUtil.modelLineToWidgetLine(...) should be patched so it's becoming responsible for returning same line number for multiple lines that form one wrapped line.


public static int modelLineToWidgetLine(ITextViewer viewer, final int modelLine) {
	int widgetLine;
	if (viewer instanceof ITextViewerExtension5) {
		ITextViewerExtension5 extension= (ITextViewerExtension5) viewer;
		widgetLine= extension.modelLine2WidgetLine(modelLine);
	} else {
		IRegion region= viewer.getVisibleRegion();
		IDocument document= viewer.getDocument();
		try {
			int visibleStartLine= document.getLineOfOffset(region.getOffset());
			int visibleEndLine= document.getLineOfOffset(region.getOffset() + region.getLength());
			if (modelLine < visibleStartLine || modelLine > visibleEndLine)
				widgetLine= -1;
			widgetLine= modelLine - visibleStartLine;
		} catch (BadLocationException x) {
			// ignore and return -1
			widgetLine= -1;
	return widgetLine;

StatusBar is showing cursor position correctly (2:34) even after patching DocumentAdapter to support word-wrap. Also Goto Line works correctly!

Patching DocumentAdapter seems to be not enough to keep editing functionality. Keyboard navigation is not fully functional (Del key does not work and some of the navigation has unexpected behaviour).

It would make sense that it's possible to wrap only visible area (not the whole IDocument). But looks like IDocumentAdapter cannot work this way

About LineNumberRulerColumn

LineNumberRulerColumn is currently using following to paint line numbers

for (int line= visibleLines.getStartLine(); line < lastLine; line++) {
	int widgetLine= JFaceTextUtil.modelLineToWidgetLine(fCachedTextViewer, line);

	if (widgetLine == -1)

	int lineHeight= fCachedTextWidget.getLineHeight(fCachedTextWidget.getOffsetAtLine(widgetLine));
	paintLine(line, y, lineHeight, gc, display);
	y += lineHeight;

If there would be a logic to have wordwrapped model then this logic could be patched by following to support word wrap:

int lastWidgetLine=-1;
int lastLineNumber = -1;
for (int line= visibleLines.getStartLine(); line < lastLine; line++) {
	int widgetLine= JFaceTextUtil.modelLineToWidgetLine(fCachedTextViewer, line);

	if (widgetLine == -1)

	int lineHeight= fCachedTextWidget.getLineHeight(fCachedTextWidget.getOffsetAtLine(widgetLine));

	if (lastWidgetLine==widgetLine) {
		paintLine(lastLineNumber, y, lineHeight, gc, display);
	} else {
		paintLine(line, y, lineHeight, gc, display);
	y += lineHeight;

How to store wrapped and unwrapped line number information about the same document?

Both of these are required:

  • Wrapped line information is for the text viewer, code navigation, vertical column annotations.
  • Unwrapped line information is required for functionalities like goto line, line numbering ruler column, current line highlight.

Also please note that changing editor size etc forces to rewrap the whole document and slows editor significiantly if the document is long.