Fixed markdown headings missing named anchors for anchor navigation

CHANGELOG.md

@@ -1,3 +1,4 @@
+- Fixed anchor link clicks (`#section`) in markdown preview not enabling the Back button; Back now returns to the position before the anchor jump
 - Fixed markdown preview not rendering images (`![alt](path)` syntax)
 - Fixed session tab blocking resize below ~600px when docked as a side panel (https://github.com/nbclaudecodegui/NetbeansClaudeCodeGui/issues/19)
 - Fixed terminal appearing blank after dismissing the model selection menu

docs/to-do.md

@@ -7,6 +7,6 @@
 - [x] Невозможно выйти из /usage по кнопке cancel. Отладить
 - [x] Не учитываются цвета Look and Feel для кнопок
 - [x] Previe markdown: не показываются изображения
-- [ ] Previe markdown: не работает навигация по линкам внутри файла
+- [x] Previe markdown: не работает навигация по линкам внутри файла
 
 # Features

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>io.github.nbclaudecodegui</groupId>
     <artifactId>netbeans-claude-code-gui</artifactId>
-    <version>0.21.50-SNAPSHOT</version>
+    <version>0.21.52-SNAPSHOT</version>
     <packaging>nbm</packaging>
     <name>Netbeans Claude Code GUI</name>
     <description>NetBeans plugin that provides a GUI for Claude Code CLI — run claude code sessions directly inside the IDE.</description>

src/main/java/io/github/nbclaudecodegui/ui/MarkdownPreviewTab.java

@@ -83,6 +83,7 @@ public class MarkdownPreviewTab extends TopComponent {
     // Navigation history
     final List<String> historyPaths = new ArrayList<>();
     final List<FileObject> historyFos = new ArrayList<>();
+    final List<String> historyAnchors = new ArrayList<>();
     int historyIndex = -1;
 
     /** The href under the mouse at last ENTERED event; null when not hovering a link. */
@@ -155,6 +156,7 @@ public static void openLive(String filePath, String content, FileObject fo) {
         // Push initial entry into history
         tab.historyPaths.add(filePath);
         tab.historyFos.add(fo);
+        tab.historyAnchors.add(null);
         tab.historyIndex = 0;
 
         OPEN_TABS.put(filePath, tab);
@@ -282,9 +284,11 @@ void navigateTo(String newPath, FileObject newFo, boolean addToHistory) {
             while (historyPaths.size() > historyIndex + 1) {
                 historyPaths.remove(historyPaths.size() - 1);
                 historyFos.remove(historyFos.size() - 1);
+                historyAnchors.remove(historyAnchors.size() - 1);
             }
             historyPaths.add(newPath);
             historyFos.add(newFo);
+            historyAnchors.add(null);
             historyIndex++;
         }
 
@@ -317,17 +321,56 @@ boolean canGoForward() {
         return historyIndex < historyPaths.size() - 1;
     }
 
+    void navigateToAnchor(String anchor) {
+        // Truncate forward entries
+        while (historyPaths.size() > historyIndex + 1) {
+            historyPaths.remove(historyPaths.size() - 1);
+            historyFos.remove(historyFos.size() - 1);
+            historyAnchors.remove(historyAnchors.size() - 1);
+        }
+        historyPaths.add(filePath);
+        historyFos.add(fileObject);
+        historyAnchors.add(anchor);
+        historyIndex++;
+        pane.scrollToReference(anchor);
+    }
+
     void navigateBack() {
         if (canGoBack()) {
             historyIndex--;
-            navigateTo(historyPaths.get(historyIndex), historyFos.get(historyIndex), false);
+            restoreHistoryEntry(historyIndex);
         }
     }
 
     void navigateForward() {
         if (canGoForward()) {
             historyIndex++;
-            navigateTo(historyPaths.get(historyIndex), historyFos.get(historyIndex), false);
+            restoreHistoryEntry(historyIndex);
+        }
+    }
+
+    private void restoreHistoryEntry(int idx) {
+        String targetPath = historyPaths.get(idx);
+        FileObject targetFo = historyFos.get(idx);
+        String anchor = historyAnchors.size() > idx ? historyAnchors.get(idx) : null;
+
+        if (targetPath.equals(filePath)) {
+            // Same file — just scroll
+            if (anchor != null) {
+                pane.scrollToReference(anchor);
+            } else {
+                // Scroll to top
+                SwingUtilities.invokeLater(() -> {
+                    if (scrollPane != null) {
+                        scrollPane.getViewport().setViewPosition(new Point(0, 0));
+                    }
+                });
+            }
+        } else {
+            navigateTo(targetPath, targetFo, false);
+            if (anchor != null) {
+                SwingUtilities.invokeLater(() -> pane.scrollToReference(anchor));
+            }
         }
     }
 
@@ -350,6 +393,10 @@ File resolveLink(String href) {
     }
 
     void openLinkInSameTab(String href) {
+        if (href != null && href.startsWith("#")) {
+            navigateToAnchor(href.substring(1));
+            return;
+        }
         File resolved = resolveLink(href);
         if (resolved != null) {
             FileObject fo = FileUtil.toFileObject(resolved);
@@ -556,6 +603,7 @@ protected void componentOpened() {
         if (historyPaths.isEmpty()) {
             historyPaths.add(path);
             historyFos.add(fo);
+            historyAnchors.add(null);
             historyIndex = 0;
         }
 

src/main/java/io/github/nbclaudecodegui/ui/common/MarkdownRenderer.java

@@ -261,20 +261,23 @@ private static String convertSegment(String text) {
 
             // --- Headings ---
             if (line.startsWith("# ")) {
-                html.append("<h1>").append(inlineToHtml(line.substring(2).trim()))
-                        .append("</h1>");
+                String heading = line.substring(2).trim();
+                html.append("<h1><a name=\"").append(slugify(heading)).append("\">")
+                        .append(inlineToHtml(heading)).append("</a></h1>");
                 i++;
                 continue;
             }
             if (line.startsWith("## ")) {
-                html.append("<h2>").append(inlineToHtml(line.substring(3).trim()))
-                        .append("</h2>");
+                String heading = line.substring(3).trim();
+                html.append("<h2><a name=\"").append(slugify(heading)).append("\">")
+                        .append(inlineToHtml(heading)).append("</a></h2>");
                 i++;
                 continue;
             }
             if (line.startsWith("### ")) {
-                html.append("<h3>").append(inlineToHtml(line.substring(4).trim()))
-                        .append("</h3>");
+                String heading = line.substring(4).trim();
+                html.append("<h3><a name=\"").append(slugify(heading)).append("\">")
+                        .append(inlineToHtml(heading)).append("</a></h3>");
                 i++;
                 continue;
             }
@@ -477,6 +480,19 @@ private static boolean isBlockStart(String line) {
                 || isTableRow(line);
     }
 
+    /**
+     * Converts heading text to a URL-friendly slug for use as a named anchor.
+     * Lowercases the text, strips non-alphanumeric characters (except spaces and hyphens),
+     * trims, replaces spaces with hyphens, and collapses consecutive hyphens.
+     */
+    static String slugify(String text) {
+        return text.toLowerCase()
+                   .replaceAll("[^a-z0-9\\s-]", "")
+                   .trim()
+                   .replaceAll("\\s+", "-")
+                   .replaceAll("-+", "-");
+    }
+
     /**
      * Escapes HTML special characters in plain text.
      *

src/test/java/io/github/nbclaudecodegui/ui/MarkdownPreviewTabTest.java

@@ -323,6 +323,60 @@ void writeExternalRoundTripsFilePath() throws Exception {
                 "savedScrollRatio must be 0.0 when no scrollPane is present");
     }
 
+    // --- Anchor history tests ---
+
+    @Test
+    void canGoBackTrueAfterNavigateToAnchor() {
+        MarkdownPreviewTab tab = new MarkdownPreviewTab();
+        tab.historyPaths.add("/file.md");
+        tab.historyFos.add(null);
+        tab.historyAnchors.add(null);
+        tab.historyIndex = 0;
+        tab.setFilePathForTest("/file.md");
+        tab.setPaneForTest(new JEditorPane());
+
+        tab.navigateToAnchor("section");
+
+        assertTrue(tab.canGoBack(), "canGoBack() should be true after navigateToAnchor()");
+    }
+
+    @Test
+    void canGoBackFalseAfterNavigateToAnchorThenBack() {
+        MarkdownPreviewTab tab = new MarkdownPreviewTab();
+        tab.historyPaths.add("/file.md");
+        tab.historyFos.add(null);
+        tab.historyAnchors.add(null);
+        tab.historyIndex = 0;
+        tab.setFilePathForTest("/file.md");
+        tab.setPaneForTest(new JEditorPane());
+
+        tab.navigateToAnchor("section");
+        tab.navigateBack();
+
+        assertFalse(tab.canGoBack(), "canGoBack() should be false after navigating back to initial entry");
+    }
+
+    @Test
+    void forwardTruncationClearsAnchorHistory() {
+        MarkdownPreviewTab tab = new MarkdownPreviewTab();
+        tab.historyPaths.add("/file.md");
+        tab.historyFos.add(null);
+        tab.historyAnchors.add(null);
+        tab.historyPaths.add("/file.md");
+        tab.historyFos.add(null);
+        tab.historyAnchors.add("old-anchor");
+        tab.historyIndex = 0;
+        tab.setFilePathForTest("/file.md");
+        tab.setPaneForTest(new JEditorPane());
+
+        // Navigate to new anchor (should truncate forward entry)
+        tab.navigateToAnchor("new-anchor");
+
+        assertEquals(2, tab.historyAnchors.size(), "History should have 2 entries after truncation and new push");
+        assertNull(tab.historyAnchors.get(0), "First entry anchor should be null");
+        assertEquals("new-anchor", tab.historyAnchors.get(1), "Second entry should be new anchor");
+    }
+
     private static List<String> menuItemLabels(JPopupMenu menu) {
         List<String> labels = new ArrayList<>();
         for (int i = 0; i < menu.getComponentCount(); i++) {

src/test/java/io/github/nbclaudecodegui/ui/common/MarkdownRendererTest.java

@@ -71,9 +71,9 @@ void testPlainTextEscaped() {
     @Test
     void testHeadings() {
         String html = MarkdownRenderer.toHtml("# H1\n## H2\n### H3");
-        assertTrue(html.contains("<h1>H1</h1>"), "h1");
-        assertTrue(html.contains("<h2>H2</h2>"), "h2");
-        assertTrue(html.contains("<h3>H3</h3>"), "h3");
+        assertTrue(html.contains("<h1>") && html.contains("H1") && html.contains("</h1>"), "h1");
+        assertTrue(html.contains("<h2>") && html.contains("H2") && html.contains("</h2>"), "h2");
+        assertTrue(html.contains("<h3>") && html.contains("H3") && html.contains("</h3>"), "h3");
     }
 
     @Test
@@ -237,4 +237,32 @@ void testInlineImageEmptyAlt() {
         assertTrue(result.contains("alt=\"\""), "empty alt");
     }
 
+    // -------------------------------------------------------------------------
+    // Bug 3: Named anchors in headings for anchor navigation
+    // -------------------------------------------------------------------------
+
+    @Test
+    void testHeadingH1HasNamedAnchor() {
+        String html = MarkdownRenderer.toHtml("# My Heading");
+        assertTrue(html.contains("<a name=\"my-heading\">"), "h1 named anchor");
+        assertTrue(html.contains("<h1>"), "h1 tag");
+    }
+
+    @Test
+    void testHeadingH2HasNamedAnchor() {
+        String html = MarkdownRenderer.toHtml("## Section Two");
+        assertTrue(html.contains("<a name=\"section-two\">"), "h2 named anchor");
+    }
+
+    @Test
+    void testHeadingH3HasNamedAnchor() {
+        String html = MarkdownRenderer.toHtml("### Sub Section");
+        assertTrue(html.contains("<a name=\"sub-section\">"), "h3 named anchor");
+    }
+
+    @Test
+    void testHeadingSlugStripNonAlphanumeric() {
+        String html = MarkdownRenderer.toHtml("# Hello, World! (2024)");
+        assertTrue(html.contains("<a name=\"hello-world-2024\">"), "slug strips punctuation");
+    }
 }