8348282: Add option for syntax highlighting in javadoc snippets

make/Docs.gmk

@@ -100,7 +100,7 @@ JAVA_WARNINGS_ARE_ERRORS ?= -Werror
 JAVADOC_OPTIONS := -use -keywords -notimestamp \
     -serialwarn -encoding ISO-8859-1 -docencoding UTF-8 -breakiterator \
     -splitIndex --system none -javafx --expand-requires transitive \
-    --override-methods=summary
+    --override-methods=summary --syntax-highlight
 
 # The reference options must stay stable to allow for comparisons across the
 # development cycle.

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/HtmlDoclet.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -311,6 +311,12 @@ protected void generateOtherFiles(ClassTree classTree)
             copyFontResources();
         }
 
+        var syntaxHighlight = options.syntaxHighlight();
+        if (syntaxHighlight) {
+            copyResource(DocPaths.HIGHLIGHT_CSS, DocPaths.RESOURCE_FILES.resolve(DocPaths.HIGHLIGHT_CSS), true);
+            copyResource(DocPaths.HIGHLIGHT_JS, DocPaths.SCRIPT_FILES.resolve(DocPaths.HIGHLIGHT_JS), true);
+        }
+
         // If a stylesheet file is not specified, copy the default stylesheet
         // and replace newline with platform-specific newline.
         if (options.stylesheetFile().isEmpty()) {

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/HtmlDocletWriter.java

@@ -511,6 +511,7 @@ public void printHtmlDocument(List<String> metakeywords,
                 .setStylesheets(configuration.getMainStylesheet(), additionalStylesheets, localStylesheets)
                 .setAdditionalScripts(configuration.getAdditionalScripts())
                 .setIndex(options.createIndex(), mainBodyScript)
+                .setSyntaxHighlight(options.syntaxHighlight())
                 .addContent(extraHeadContent);
 
         HtmlDocument htmlDocument = new HtmlDocument(

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/HtmlOptions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -198,6 +198,11 @@ public class HtmlOptions extends BaseOptions {
      */
     private String stylesheetFile = "";
 
+    /**
+     * Argument for command line option {@code --syntax-highlight}.
+     */
+    private boolean syntaxHighlight = false;
+
     /**
      * Argument for command-line option {@code -tagletpath}.
      * The path to Taglets
@@ -423,6 +428,14 @@ public boolean process(String opt, List<String> args) {
                     }
                 },
 
+                new Option(resources, "--syntax-highlight") {
+                    @Override
+                    public boolean process(String opt, List<String> args) {
+                        syntaxHighlight = true;
+                        return true;
+                    }
+                },
+
                 new Option(resources, "-tag", 1) {
                     @Override
                     public boolean process(String opt, List<String> args) {
@@ -806,6 +819,13 @@ String stylesheetFile() {
         return stylesheetFile;
     }
 
+    /**
+     * Argument for command line option {@code --syntax-highlight}.
+     * True if command line option "--syntax-highlight" is used and syntax
+     * highlighting should be enabled. Default value is false.
+     */
+    public boolean syntaxHighlight() { return syntaxHighlight; }
+
     /**
      * Argument for command-line option {@code -tagletpath}.
      * The path to Taglets

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/markup/Head.java

@@ -70,6 +70,7 @@ public class Head extends Content {
     private final List<Content> extraContent;
     private boolean addDefaultScript = true;
     private DocPath canonicalLink;
+    private boolean syntaxHighlight = false;
 
     /**
      * Creates a {@code Head} object, for a given file and HTML version.
@@ -238,6 +239,16 @@ public void setCanonicalLink(DocPath link) {
         this.canonicalLink = link;
     }
 
+    /**
+     * Enables or disables support for syntax highlighting.
+     * @param value {@code true} to enable syntax highligting
+     * @return this object
+     */
+    public Head setSyntaxHighlight(boolean value) {
+        this.syntaxHighlight = value;
+        return this;
+    }
+
     /**
      * Adds additional content to be included in the HEAD element.
      *
@@ -339,6 +350,11 @@ private void addStylesheets(HtmlTree head) {
             addStylesheet(head, DocPaths.RESOURCE_FILES.resolve(path));
         }
 
+        if (syntaxHighlight) {
+            addStylesheet(head, DocPaths.RESOURCE_FILES.resolve(DocPaths.HIGHLIGHT_CSS));
+            addScriptElement(head, DocPaths.HIGHLIGHT_JS);
+        }
+
         for (DocPath path : localStylesheets) {
             // Local stylesheets are contained in doc-files, so omit resource-files prefix
             addStylesheet(head, path);

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/resources/highlight.css

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl/
+ */
+/* Syntax highlight style sheet */
+.hljs-title.function_,
+.hljs-template-variable {
+    color: #00738F;
+}
+.hljs-code,
+.hljs-comment,
+.hljs-quote {
+    color: #6e6e71;
+    font-style: italic;
+}
+.hljs-meta {
+    color: #836F00;
+}
+.hljs-symbol,
+.hljs-template-tag,
+.hljs-keyword,
+.hljs-literal,
+.hljs-name,
+.hljs-built_in,
+.hljs-char.escape_ {
+    color: #0C40C2;
+}
+.hljs-variable,
+.hljs-property,
+.hljs-attr,
+.hljs-section {
+    color: #841191;
+}
+.hljs-attribute {
+    color: #164ad9;
+}
+.hljs-regexp,
+.hljs-number {
+    color: #104BEB;
+}
+.hljs-link {
+    color: #47688a;
+}
+.hljs-string {
+    color: #008313;
+}
+.hljs-doctag {
+    text-decoration: underline;
+}
+.hljs-emphasis {
+    font-style: italic;
+}
+.hljs-strong {
+    font-weight: bold;
+}
+.hljs-subst,
+.hljs-title,
+.hljs-params,
+.hljs-bullet,
+.hljs-formula,
+.hljs-tag,
+.hljs-type {
+    /* ignored */
+}
+