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Add SourceViewer#computeStyleRanges() to highlight external documents #3868

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30f58ec
Add SourceViewer#computeStyleRanges() to highlight external documents
tobias-melcher Apr 6, 2026
c47d26a
Fix exception-safety and Javadoc of SourceViewer#computeStyleRanges()
tobias-melcher Apr 17, 2026
d6456a7
add SourceViewerComputeStyleRangesTest
tobias-melcher Apr 18, 2026
392609f
Fix partitioner leak and add null guard in
tobias-melcher Apr 19, 2026
3142c65
Simplify SourceViewer#computeStyleRanges() and fix finally-block
tobias-melcher Apr 22, 2026
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103 changes: 103 additions & 0 deletions bundles/org.eclipse.jface.text/src/org/eclipse/jface/text/source/SourceViewer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,15 +24,19 @@
import java.util.Stack;

import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.StyleRange;
import org.eclipse.swt.custom.StyledText;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Layout;
import org.eclipse.swt.widgets.ScrollBar;

import org.eclipse.core.runtime.Assert;

import org.eclipse.jface.internal.text.NonDeletingPositionUpdater;
import org.eclipse.jface.internal.text.StickyHoverManager;
import org.eclipse.jface.internal.text.codemining.CodeMiningManager;
Expand All @@ -46,7 +50,9 @@
import org.eclipse.jface.text.IAutoEditStrategy;
import org.eclipse.jface.text.IBlockTextSelection;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IDocumentExtension3;
import org.eclipse.jface.text.IDocumentExtension4;
import org.eclipse.jface.text.IDocumentPartitioner;
import org.eclipse.jface.text.IPositionUpdater;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.IRewriteTarget;
Expand All @@ -56,8 +62,11 @@
import org.eclipse.jface.text.ITextSelection;
import org.eclipse.jface.text.ITextViewerExtension2;
import org.eclipse.jface.text.ITextViewerLifecycle;
import org.eclipse.jface.text.ITypedRegion;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.TextPresentation;
import org.eclipse.jface.text.TextUtilities;
import org.eclipse.jface.text.TextViewer;
import org.eclipse.jface.text.codemining.ICodeMiningProvider;
import org.eclipse.jface.text.contentassist.IContentAssistant;
Expand All @@ -71,6 +80,8 @@
import org.eclipse.jface.text.hyperlink.IHyperlinkDetector;
import org.eclipse.jface.text.information.IInformationPresenter;
import org.eclipse.jface.text.presentation.IPresentationReconciler;
import org.eclipse.jface.text.presentation.IPresentationReconcilerExtension;
import org.eclipse.jface.text.presentation.IPresentationRepairer;
import org.eclipse.jface.text.projection.ChildDocument;
import org.eclipse.jface.text.quickassist.IQuickAssistAssistant;
import org.eclipse.jface.text.quickassist.IQuickAssistInvocationContext;
Expand Down Expand Up @@ -1393,4 +1404,96 @@ private void uninstallTextViewer() {
lifecycles.clear();
}

/**
* Computes syntax-highlighting style ranges for a region of an external document using this
* viewer's configured presentation reconciler and partitioner.
* <p>
* This is useful when you want to syntax-color content that is <em>not</em> the document
* currently displayed in the viewer — for example, to preview or render a snippet with the same
* language rules that are active in this viewer.
* </p>
* <p>
* The viewer's partitioner is temporarily connected to the given document so that its
* presentation repairers can compute the correct highlighting. The viewer's own document is not
* affected. However, if the original document uses a named partitioning (via
* {@link IDocumentExtension3}), its partitioner is briefly disconnected from the original
* document and reconnected to {@code document} for the duration of the call; it is always
* reconnected to the original document before this method returns, even if an exception is
* thrown.
* </p>
* <p>
* <strong>Note:</strong> This method must be called from the SWT UI thread.
* </p>
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@vogella vogella Apr 17, 2026

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The Javadoc says "The viewer's own document is not affected", but this method temporarily disconnects the original document's partitioner and reconnects it only on the happy path. Worth documenting the side effect on the original document's partitioner state, and the UI-thread-only assumption.

*
* @param document the external document whose content should be highlighted; must not be
* {@code null} and must use the same language/content type as this viewer; must
* implement {@link org.eclipse.jface.text.IDocumentExtension3} — if either
* {@code document} or the viewer's current document does not implement
* {@code IDocumentExtension3}, an empty list is returned
* @param region the region within {@code document} for which style ranges are computed; must
* not be {@code null}
* @return the list of {@link org.eclipse.swt.custom.StyleRange}s covering the given region, as
* produced by this viewer's presentation reconciler; never {@code null}, may be empty
* if no repairer is registered for the content type, or if either document does not
* implement {@code IDocumentExtension3}
* @throws BadLocationException if {@code region} is outside the bounds of {@code document}
* @since 3.31
*/
public List<StyleRange> computeStyleRanges(IDocument document, IRegion region) throws BadLocationException {
Assert.isTrue(Display.getCurrent() != null, "computeStyleRanges must be called from SWT UI thread"); //$NON-NLS-1$
IDocument originalDocument= getDocument();
Assert.isNotNull(originalDocument, "viewer must have a document before calling computeStyleRanges"); //$NON-NLS-1$
List<StyleRange> result= new ArrayList<>();
String partitioning= IDocumentExtension3.DEFAULT_PARTITIONING;
IPresentationReconciler reconciler= fPresentationReconciler;
if (reconciler instanceof IPresentationReconcilerExtension ext) {
String extPartitioning= ext.getDocumentPartitioning();
if (extPartitioning != null && !extPartitioning.isEmpty()) {
partitioning= extPartitioning;
}
}
IDocumentPartitioner originalDocumentPartitioner= null;
IDocumentExtension3 documentExt= null;
if (document instanceof IDocumentExtension3 docExt
&& originalDocument instanceof IDocumentExtension3 originalExt) {
documentExt= docExt;
originalDocumentPartitioner= originalExt.getDocumentPartitioner(partitioning);
} else {
return result;
}
IDocumentPartitioner externalDocPartitioner= null;
try {
// Temporarily reconnect the partitioner to the external document so that
// presentation repairers compute highlighting against the right content.
// The finally block always restores both documents to their original state.
externalDocPartitioner= documentExt.getDocumentPartitioner(partitioning);
if (originalDocumentPartitioner != null) {
originalDocumentPartitioner.disconnect();
originalDocumentPartitioner.connect(document);
documentExt.setDocumentPartitioner(partitioning, originalDocumentPartitioner);
}
TextPresentation presentation= new TextPresentation(region, Math.max(region.getLength() / 10, 16));
ITypedRegion[] partitioningRegions= TextUtilities.computePartitioning(document, partitioning, region.getOffset(),
region.getLength(), false);
for (ITypedRegion partitioningRegion : partitioningRegions) {
IPresentationRepairer repairer= reconciler.getRepairer(partitioningRegion.getType());
if (repairer != null) {
repairer.setDocument(document);
repairer.createPresentation(presentation, partitioningRegion);
repairer.setDocument(originalDocument);
}
}
var it= presentation.getAllStyleRangeIterator();
while (it.hasNext()) {
result.add(it.next());
}
return result;
} finally {
if (originalDocumentPartitioner != null) {
originalDocumentPartitioner.disconnect();
originalDocumentPartitioner.connect(originalDocument);
documentExt.setDocumentPartitioner(partitioning, externalDocPartitioner);
}
}
}
}
2 changes: 2 additions & 0 deletions tests/org.eclipse.jface.text.tests/src/org/eclipse/jface/text/tests/JFaceTextTestSuite.java
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Expand Up @@ -33,6 +33,7 @@
import org.eclipse.jface.text.tests.rules.WordRuleTest;
import org.eclipse.jface.text.tests.source.AnnotationRulerColumnTest;
import org.eclipse.jface.text.tests.source.LineNumberRulerColumnTest;
import org.eclipse.jface.text.tests.source.SourceViewerComputeStyleRangesTest;
import org.eclipse.jface.text.tests.source.inlined.AnnotationOnTabTest;
import org.eclipse.jface.text.tests.source.inlined.LineContentBoundsDrawingTest;
import org.eclipse.jface.text.tests.templates.persistence.TemplatePersistenceDataTest;
Expand All @@ -46,6 +47,7 @@
@SelectClasses({
AnnotationRulerColumnTest.class,
LineNumberRulerColumnTest.class,
SourceViewerComputeStyleRangesTest.class,
HTML2TextReaderTest.class,
TextHoverPopupTest.class,
TextPresentationTest.class,
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