Fixed markdown preview not rendering images with relative paths

CHANGELOG.md

@@ -1,6 +1,6 @@
 - Added minimum tested Claude Code CLI version (2.1.78) to installation requirements (https://github.com/nbclaudecodegui/NetbeansClaudeCodeGui/issues/29)
 - 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 markdown preview not rendering images with relative paths (`![alt](path)` syntax)
 - Fixed session tab blocking resize below ~600px when docked as a side panel (https://github.com/nbclaudecodegui/NetbeansClaudeCodeGui/issues/19)
 - Added alphabetical sorting to the "Select Project" dropdown (https://github.com/nbclaudecodegui/NetbeansClaudeCodeGui/issues/21)
 - Improved error panel on process start failure: shows Working Directory and CLAUDE_CONFIG_DIR fields (before Command and Error) for easier diagnosis; all fields have a right-click Copy menu; fixed "Restart Advanced…" not dismissing the error panel

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>io.github.nbclaudecodegui</groupId>
     <artifactId>netbeans-claude-code-gui</artifactId>
-    <version>0.21.53-SNAPSHOT</version>
+    <version>0.21.55-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

@@ -80,6 +80,9 @@ public class MarkdownPreviewTab extends TopComponent {
     /** Absolute path key used to identify this tab in {@link #OPEN_TABS}. */
     String filePath;
 
+    /** Parent directory of {@link #filePath}; used to resolve relative image paths. */
+    String baseDirPath;
+
     // Navigation history
     final List<String> historyPaths = new ArrayList<>();
     final List<FileObject> historyFos = new ArrayList<>();
@@ -133,9 +136,10 @@ public static void openLive(String filePath, String content, FileObject fo) {
         MarkdownPreviewTab tab = new MarkdownPreviewTab();
         tab.filePath = filePath;
         tab.fileObject = fo;
+        tab.baseDirPath = new java.io.File(filePath).getParent();
 
         String html = MarkdownRenderer.toHtml(content != null ? content : "");
-        tab.pane = MarkdownRenderer.createOutputPane(html, new java.io.File(filePath).getParent());
+        tab.pane = MarkdownRenderer.createOutputPane(html, tab.baseDirPath);
 
         String name = new java.io.File(filePath).getName();
         tab.setDisplayName("Preview: " + name);
@@ -171,7 +175,8 @@ public static void openLive(String filePath, String content, FileObject fo) {
      * @param markdown markdown text to render
      */
     public void updateContent(String markdown) {
-        String html = MarkdownRenderer.toHtml(markdown != null ? markdown : "");
+        String html = MarkdownRenderer.resolveImagePaths(
+                MarkdownRenderer.toHtml(markdown != null ? markdown : ""), baseDirPath);
         SwingUtilities.invokeLater(() -> {
             if (pane == null) return;
             if (scrollPane == null) {
@@ -298,6 +303,7 @@ void navigateTo(String newPath, FileObject newFo, boolean addToHistory) {
         }
         this.filePath = newPath;
         this.fileObject = newFo;
+        this.baseDirPath = new File(newPath).getParent();
         OPEN_TABS.put(newPath, this);
 
         setDisplayName("Preview: " + new File(newPath).getName());
@@ -583,8 +589,9 @@ protected void componentOpened() {
         FileObject fo = FileUtil.toFileObject(f);
         if (pane == null) {
             try {
+                baseDirPath = f.getParent();
                 String content = fo != null ? fo.asText() : "";
-                pane = MarkdownRenderer.createOutputPane(MarkdownRenderer.toHtml(content));
+                pane = MarkdownRenderer.createOutputPane(MarkdownRenderer.toHtml(content), baseDirPath);
             } catch (IOException e) {
                 return;
             }

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

@@ -75,18 +75,28 @@ public static JEditorPane createOutputPane(String html) {
      */
     public static JEditorPane createOutputPane(String html, String baseDirPath) {
         JEditorPane pane = createOutputPane();
-        if (baseDirPath != null) {
-            try {
-                ((HTMLDocument) pane.getDocument()).setBase(
-                        new java.net.URL("file://" + baseDirPath + "/"));
-            } catch (java.net.MalformedURLException ignored) {
-                // fall through — relative images won't resolve but nothing breaks
-            }
-        }
-        pane.setText(html);
+        pane.setText(resolveImagePaths(html, baseDirPath));
         return pane;
     }
 
+    /**
+     * Replaces relative {@code src} attributes in {@code <img>} tags with absolute
+     * {@code file://} URIs so Swing's HTMLEditorKit can load them regardless of the
+     * document base URL setting.
+     *
+     * @param html        HTML fragment (may contain {@code <img src="...">} tags)
+     * @param baseDirPath absolute directory path of the file being rendered, or null
+     * @return the HTML with relative image paths resolved, or the original HTML if
+     *         {@code baseDirPath} is null
+     */
+    public static String resolveImagePaths(String html, String baseDirPath) {
+        if (baseDirPath == null) return html;
+        String base = baseDirPath.replace("\\", "/");
+        return html.replaceAll(
+                "src=\"(?!https?://|file://|data:)([^\"]+)\"",
+                "src=\"file://" + base + "/$1\"");
+    }
+
     /**
      * Creates and configures a {@link JEditorPane} for rendering chat output with no initial content.
      *

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

@@ -265,4 +265,50 @@ void testHeadingSlugStripNonAlphanumeric() {
         String html = MarkdownRenderer.toHtml("# Hello, World! (2024)");
         assertTrue(html.contains("<a name=\"hello-world-2024\">"), "slug strips punctuation");
     }
+
+    // -------------------------------------------------------------------------
+    // resolveImagePaths()
+    // -------------------------------------------------------------------------
+
+    @Test
+    void testResolveImagePathsRelative() {
+        String html = "<img src=\"screenshots/overview.png\" alt=\"\">";
+        String result = MarkdownRenderer.resolveImagePaths(html, "/docs");
+        assertEquals("<img src=\"file:///docs/screenshots/overview.png\" alt=\"\">", result);
+    }
+
+    @Test
+    void testResolveImagePathsAbsoluteHttpUnchanged() {
+        String html = "<img src=\"https://example.com/img.png\" alt=\"\">";
+        String result = MarkdownRenderer.resolveImagePaths(html, "/docs");
+        assertEquals(html, result);
+    }
+
+    @Test
+    void testResolveImagePathsFileUriUnchanged() {
+        String html = "<img src=\"file:///abs/path/img.png\" alt=\"\">";
+        String result = MarkdownRenderer.resolveImagePaths(html, "/docs");
+        assertEquals(html, result);
+    }
+
+    @Test
+    void testResolveImagePathsDataUriUnchanged() {
+        String html = "<img src=\"data:image/png;base64,abc\" alt=\"\">";
+        String result = MarkdownRenderer.resolveImagePaths(html, "/docs");
+        assertEquals(html, result);
+    }
+
+    @Test
+    void testResolveImagePathsNullBaseDirReturnsUnchanged() {
+        String html = "<img src=\"img.png\" alt=\"\">";
+        String result = MarkdownRenderer.resolveImagePaths(html, null);
+        assertEquals(html, result);
+    }
+
+    @Test
+    void testResolveImagePathsWindowsBackslashesNormalized() {
+        String html = "<img src=\"img.png\" alt=\"\">";
+        String result = MarkdownRenderer.resolveImagePaths(html, "C:\\docs\\project");
+        assertEquals("<img src=\"file://C:/docs/project/img.png\" alt=\"\">", result);
+    }
 }