Implement `DocumentSymbolProvider`.

src/document.ts

@@ -8,6 +8,7 @@
 import * as vscode from 'vscode';
 import { FoldingRangeContext } from './folding';
 import Preview from './preview';
+import { DocumentSymbolContext } from './symbol';
 
 /**
  * Manages context and events for a document.
@@ -30,7 +31,9 @@ export default class Document {
 
     static update(event: vscode.TextDocumentChangeEvent) {
         const documentContext = Document.get(event.document);
-        documentContext?.foldingRange.update(event.contentChanges);
+        if (documentContext?.foldingRange.update(event.contentChanges)) {
+            documentContext.symbol.update(documentContext.foldingRange.values);
+        }
     }
 
     static save(document: vscode.TextDocument) {
@@ -50,6 +53,8 @@ export default class Document {
 
     readonly foldingRange = new FoldingRangeContext(this.document);
 
+    readonly symbol = new DocumentSymbolContext(this);
+
     private preview?: Preview;
 
     initPreview() {

src/extension.ts

@@ -11,6 +11,7 @@ import Options from './options';
 import Preview from './preview';
 import { CompletionItemProvider } from './completion';
 import { FoldingRangeProvider } from './folding';
+import { DocumentSymbolProvider } from './symbol';
 
 export function activate(context: vscode.ExtensionContext) {
     context.subscriptions.push(
@@ -21,6 +22,7 @@ export function activate(context: vscode.ExtensionContext) {
         vscode.commands.registerTextEditorCommand('texinfo.showPreview', Preview.show),
         vscode.languages.registerCompletionItemProvider('texinfo', new CompletionItemProvider(), '@'),
         vscode.languages.registerFoldingRangeProvider('texinfo', new FoldingRangeProvider()),
+        vscode.languages.registerDocumentSymbolProvider('texinfo', new DocumentSymbolProvider()),
     );
 }
 

src/symbol.ts

@@ -0,0 +1,81 @@
+/**
+ * symbol.ts
+ * 
+ * @author CismonX <admin@cismon.net>
+ * @license MIT
+ */
+
+import * as vscode from 'vscode';
+import Document from './document';
+import { FoldingRange } from './folding';
+
+/**
+ * Provide document symbol information for Texinfo documents.
+ */
+export class DocumentSymbolProvider implements vscode.DocumentSymbolProvider {
+
+    provideDocumentSymbols(document: vscode.TextDocument) {
+        return Document.of(document).symbol.values;
+    }
+}
+
+/**
+ * Context for symbols in a Texinfo document.
+ */
+export class DocumentSymbolContext {
+
+    private document = this.documentContext.document;
+
+    private symbols?: vscode.DocumentSymbol[];
+
+    private foldingRanges?: FoldingRange[];
+
+    get values() {
+        return this.symbols ??= this.calculcateDocumentSymbols();
+    }
+
+    update(foldingRanges: FoldingRange[]) {
+        this.foldingRanges = foldingRanges;
+        this.symbols = undefined;
+    }
+
+    /**
+     * Calculate (very limited) document symbols based on folding ranges.
+     */
+    private calculcateDocumentSymbols() {
+        this.symbols = [];
+        if (this.foldingRanges === undefined) {
+            this.foldingRanges = this.documentContext.foldingRange.values;
+        }
+        const ranges = Array<RangeNode>(this.document.lineCount);
+        this.foldingRanges.forEach(range => {
+            if (range.kind !== undefined) return;
+            ranges[range.start] = { name: range.name, end: range.end };
+        });
+        return this.symbols = this.rangeToSymbols(ranges, 0, ranges.length);
+    }
+
+    private rangeToSymbols(ranges: RangeNode[], start: number, end: number) {
+        const symbols = <vscode.DocumentSymbol[]>[];
+        for (let idx = start; idx < end; ++idx) {
+            const node = ranges[idx];
+            if (node === undefined) {
+                continue;
+            }
+            const startPosition = new vscode.Position(idx, 0);
+            const endFirstLine = new vscode.Position(idx, Number.MAX_SAFE_INTEGER);
+            const endLastLine = new vscode.Position(node.end, Number.MAX_SAFE_INTEGER);
+            const range = new vscode.Range(startPosition, endLastLine);
+            const selection = new vscode.Range(startPosition, endFirstLine);
+            const symbol = new vscode.DocumentSymbol('@' + node.name, '', vscode.SymbolKind.String, range, selection);
+            symbol.children = this.rangeToSymbols(ranges, idx + 1, node.end);
+            symbols.push(symbol);
+            idx = node.end;
+        }
+        return symbols;
+    }
+
+    constructor(private readonly documentContext: Document) {}
+}
+
+type RangeNode = { name: string, end: number } | undefined;