find matching 'begin' - 'end' and highlight them - eclipse-rcp

Question

I am a newbie in developing a DSL in Xtext. I would like to add a feature of highlighting the matching start and end of a code block. In my language every function must start with 'begin' and end with 'end' and same with if conditions and loops. I need to highlight the matching/corresponding 'end' when the cursor is on the 'begin'. for example below, I need to highlight the corresponding first 'end' when the cursor is on the second 'begin':
function X
begin
if a>b
begin
a=b;
end
end
Any help with that please?
Thanks

Answer 1

i dont think the support for that is very good. if you can live with a minor solution you could try the following
The Grammar
Model:
greetings+=Greeting*;
Greeting:
'if' name=ID 'endif';
In the UiModule
#Override
public ICharacterPairMatcher bindICharacterPairMatcher() {
return new MyDslCharacterPairMatcher(new char[] { '(', ')', '{', '}', '[', ']' });
}
with
public class MyDslCharacterPairMatcher extends DefaultCharacterPairMatcher {
public MyDslCharacterPairMatcher(char[] chars) {
super(chars);
}
#Override
public IRegion match(IDocument document, int offset, int length) {
if (document instanceof IXtextDocument) {
IXtextDocument xtextDocument = (IXtextDocument)document;
IRegion result = xtextDocument.readOnly(new IUnitOfWork<IRegion, XtextResource>() {
#Override
public IRegion exec(XtextResource state) throws Exception {
MyDslGrammarAccess ga = state.getResourceServiceProvider().get(MyDslGrammarAccess.class);
ICompositeNode root = state.getParseResult().getRootNode();
ILeafNode matchNode = NodeModelUtils.findLeafNodeAtOffset(root, offset);
EObject object = NodeModelUtils.findActualSemanticObjectFor(matchNode);
if (object instanceof Greeting) {
Greeting g = (Greeting)object;
if (matchNode.getGrammarElement() == ga.getGreetingAccess().getIfKeyword_0()) {
ICompositeNode objectNode = NodeModelUtils.findActualNodeFor(object);
for (INode n : objectNode.getAsTreeIterable()) {
if (n.getGrammarElement() != null && n.getGrammarElement() == ga.getGreetingAccess().getEndifKeyword_2()) {
return new Region(n.getOffset(), n.getLength());
}
}
}
if (matchNode.getGrammarElement() == ga.getGreetingAccess().getEndifKeyword_2()) {
ICompositeNode objectNode = NodeModelUtils.findActualNodeFor(object);
for (INode n : objectNode.getAsTreeIterable()) {
if (n.getGrammarElement() != null && n.getGrammarElement() == ga.getGreetingAccess().getIfKeyword_0()) {
return new Region(n.getOffset(), n.getLength());
}
}
}
}
return null;
}
});
if (result != null) {
return result;
}
}
return super.match(document, offset, length);
}
}
Unfortunately JFace only Highlight a single Character.
if you want more i think you have to hook into IOccurrenceComputer
(you have to have mark occurences on then)
package org.xtext.example.mydsl1.ui;
import java.util.HashMap;
import java.util.Map;
import org.eclipse.core.runtime.SubMonitor;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.jface.text.ITextSelection;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.source.Annotation;
import org.eclipse.xtext.nodemodel.ICompositeNode;
import org.eclipse.xtext.nodemodel.ILeafNode;
import org.eclipse.xtext.nodemodel.INode;
import org.eclipse.xtext.nodemodel.util.NodeModelUtils;
import org.eclipse.xtext.resource.XtextResource;
import org.eclipse.xtext.ui.editor.XtextEditor;
import org.eclipse.xtext.ui.editor.model.IXtextDocument;
import org.eclipse.xtext.ui.editor.occurrences.DefaultOccurrenceComputer;
import org.eclipse.xtext.util.CancelIndicator;
import org.eclipse.xtext.util.TextRegion;
import org.eclipse.xtext.util.concurrent.CancelableUnitOfWork;
import org.xtext.example.mydsl1.myDsl.Greeting;
import org.xtext.example.mydsl1.services.MyDslGrammarAccess;
public class MyDslOccurrenceComputer extends DefaultOccurrenceComputer {
#Override
public Map<Annotation, Position> createAnnotationMap(XtextEditor editor,
ITextSelection selection, SubMonitor monitor) {
final IXtextDocument document = editor.getDocument();
if (document != null) {
Map<Annotation, Position> result = document.readOnly(new CancelableUnitOfWork<Map<Annotation, Position>, XtextResource>() {
#Override
public Map<Annotation, Position> exec(XtextResource state,
final CancelIndicator cancelIndicator) throws Exception {
MyDslGrammarAccess ga = state.getResourceServiceProvider()
.get(MyDslGrammarAccess.class);
ICompositeNode root = state.getParseResult().getRootNode();
ILeafNode matchNode = NodeModelUtils.findLeafNodeAtOffset(
root, selection.getOffset());
EObject object = NodeModelUtils
.findActualSemanticObjectFor(matchNode);
if (object instanceof Greeting) {
Greeting g = (Greeting) object;
if (matchNode.getGrammarElement() == ga
.getGreetingAccess().getIfKeyword_0()) {
ICompositeNode objectNode = NodeModelUtils
.findActualNodeFor(object);
for (INode n : objectNode.getAsTreeIterable()) {
if (n.getGrammarElement() != null
&& n.getGrammarElement() == ga
.getGreetingAccess()
.getEndifKeyword_3()) {
Map<Annotation, Position> result = new HashMap<>();
addOccurrenceAnnotation(
DECLARATION_ANNOTATION_TYPE,
document,
new TextRegion(matchNode
.getOffset(), matchNode
.getLength()), result);
addOccurrenceAnnotation(
OCCURRENCE_ANNOTATION_TYPE,
document,
new TextRegion(n.getOffset(), n
.getLength()), result);
return result;
}
}
}
if (matchNode.getGrammarElement() == ga
.getGreetingAccess().getEndifKeyword_3()) {
ICompositeNode objectNode = NodeModelUtils
.findActualNodeFor(object);
for (INode n : objectNode.getAsTreeIterable()) {
if (n.getGrammarElement() != null
&& n.getGrammarElement() == ga
.getGreetingAccess()
.getIfKeyword_0()) {
Map<Annotation, Position> result = new HashMap<>();
addOccurrenceAnnotation(
DECLARATION_ANNOTATION_TYPE,
document,
new TextRegion(matchNode
.getOffset(), matchNode
.getLength()), result);
addOccurrenceAnnotation(
OCCURRENCE_ANNOTATION_TYPE,
document,
new TextRegion(n.getOffset(), n
.getLength()), result);
return result;
}
}
}
}
return null;
}
});
if (result != null) {
return result;
}
}
return super.createAnnotationMap(editor, selection, monitor);
}
}