Add Markdown syntax highlighting to the script editor

editor/plugins/script_editor_plugin.cpp

@@ -259,6 +259,52 @@ Ref<EditorSyntaxHighlighter> EditorJSONSyntaxHighlighter::_create() const {
 	return syntax_highlighter;
 }
 
+////
+
+void EditorMarkdownSyntaxHighlighter::_update_cache() {
+	highlighter->set_text_edit(text_edit);
+	highlighter->clear_keyword_colors();
+	highlighter->clear_member_keyword_colors();
+	highlighter->clear_color_regions();
+
+	// Disable automatic symbolic highlights, as these don't make sense for prose.
+	highlighter->set_symbol_color(EDITOR_GET("text_editor/theme/highlighting/text_color"));
+	highlighter->set_number_color(EDITOR_GET("text_editor/theme/highlighting/text_color"));
+	highlighter->set_member_variable_color(EDITOR_GET("text_editor/theme/highlighting/text_color"));
+	highlighter->set_function_color(EDITOR_GET("text_editor/theme/highlighting/text_color"));
+
+	// Headings (any level).
+	const Color function_color = EDITOR_GET("text_editor/theme/highlighting/function_color");
+	highlighter->add_color_region("#", "", function_color);
+
+	// Bold.
+	highlighter->add_color_region("**", "**", function_color);
+	// `__bold__` syntax is not supported as color regions must begin with a symbol,
+	// not a character that is valid in an identifier.
+
+	// Code (both inline code and triple-backticks code blocks).
+	const Color code_color = EDITOR_GET("text_editor/theme/highlighting/engine_type_color");
+	highlighter->add_color_region("`", "`", code_color);
+
+	// Link (both references and inline links with URLs). The URL is not highlighted.
+	const Color link_color = EDITOR_GET("text_editor/theme/highlighting/keyword_color");
+	highlighter->add_color_region("[", "]", link_color);
+
+	// Quote.
+	const Color quote_color = EDITOR_GET("text_editor/theme/highlighting/string_color");
+	highlighter->add_color_region(">", "", quote_color, true);
+
+	// HTML comment, which is also supported in Markdown.
+	const Color comment_color = EDITOR_GET("text_editor/theme/highlighting/comment_color");
+	highlighter->add_color_region("<!--", "-->", comment_color);
+}
+
+Ref<EditorSyntaxHighlighter> EditorMarkdownSyntaxHighlighter::_create() const {
+	Ref<EditorMarkdownSyntaxHighlighter> syntax_highlighter;
+	syntax_highlighter.instantiate();
+	return syntax_highlighter;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 /*** SCRIPT EDITOR ****/
@@ -4331,6 +4377,10 @@ ScriptEditor::ScriptEditor(WindowWrapper *p_wrapper) {
 	json_syntax_highlighter.instantiate();
 	register_syntax_highlighter(json_syntax_highlighter);
 
+	Ref<EditorMarkdownSyntaxHighlighter> markdown_syntax_highlighter;
+	markdown_syntax_highlighter.instantiate();
+	register_syntax_highlighter(markdown_syntax_highlighter);
+
 	_update_online_doc();
 }
 

editor/plugins/script_editor_plugin.h

@@ -120,6 +120,24 @@ public:
 	EditorJSONSyntaxHighlighter() { highlighter.instantiate(); }
 };
 
+class EditorMarkdownSyntaxHighlighter : public EditorSyntaxHighlighter {
+	GDCLASS(EditorMarkdownSyntaxHighlighter, EditorSyntaxHighlighter)
+
+private:
+	Ref<CodeHighlighter> highlighter;
+
+public:
+	virtual void _update_cache() override;
+	virtual Dictionary _get_line_syntax_highlighting_impl(int p_line) override { return highlighter->get_line_syntax_highlighting(p_line); }
+
+	virtual PackedStringArray _get_supported_languages() const override { return PackedStringArray{ "md", "markdown" }; }
+	virtual String _get_name() const override { return TTR("Markdown"); }
+
+	virtual Ref<EditorSyntaxHighlighter> _create() const override;
+
+	EditorMarkdownSyntaxHighlighter() { highlighter.instantiate(); }
+};
+
 ///////////////////////////////////////////////////////////////////////////////
 
 class ScriptEditorQuickOpen : public ConfirmationDialog {