LibSyntax+LibGUI+LibJS: Move JS syntax highlighter to LibJS

This is a little bit messy but the basic idea is:

Syntax::Highlighter now has a Syntax::HighlighterClient to talk to the
outside world. It mostly communicates in LibGUI primitives that are
available in headers, so inlineable.

GUI::TextEditor inherits from Syntax::HighlighterClient.

This let us to move GUI::JSSyntaxHighlighter to JS::SyntaxHighlighter
and remove LibGUI's dependency on LibJS.

Userland/Applications/Browser/BrowserConsoleClient.cpp

@@ -28,13 +28,10 @@
 #include "ConsoleWidget.h"
 #include <AK/StringBuilder.h>
 #include <LibGUI/BoxLayout.h>
-#include <LibGUI/JSSyntaxHighlighter.h>
 #include <LibGUI/TextBox.h>
 #include <LibWeb/DOM/DocumentType.h>
-#include <LibWeb/DOM/ElementFactory.h>
 #include <LibWeb/DOM/Text.h>
 #include <LibWeb/DOMTreeModel.h>
-#include <LibWeb/HTML/HTMLBodyElement.h>
 
 namespace Browser {
 

Userland/Applications/Browser/ConsoleWidget.cpp

@@ -28,13 +28,13 @@
 #include <AK/StringBuilder.h>
 #include <LibGUI/BoxLayout.h>
 #include <LibGUI/Button.h>
-#include <LibGUI/JSSyntaxHighlighter.h>
 #include <LibGUI/TextBox.h>
 #include <LibGfx/FontDatabase.h>
 #include <LibJS/Interpreter.h>
 #include <LibJS/MarkupGenerator.h>
 #include <LibJS/Parser.h>
 #include <LibJS/Runtime/Error.h>
+#include <LibJS/SyntaxHighlighter.h>
 #include <LibWeb/DOM/DocumentType.h>
 #include <LibWeb/DOM/ElementFactory.h>
 #include <LibWeb/DOM/Text.h>
@@ -66,7 +66,7 @@ ConsoleWidget::ConsoleWidget()
     bottom_container.set_fixed_height(22);
 
     m_input = bottom_container.add<GUI::TextBox>();
-    m_input->set_syntax_highlighter(make<GUI::JSSyntaxHighlighter>());
+    m_input->set_syntax_highlighter(make<JS::SyntaxHighlighter>());
     // FIXME: Syntax Highlighting breaks the cursor's position on non fixed-width fonts.
     m_input->set_font(Gfx::FontDatabase::default_fixed_width_font());
     m_input->set_history_enabled(true);

Userland/Applications/Spreadsheet/CellSyntaxHighlighter.cpp

@@ -25,7 +25,6 @@
  */
 
 #include "CellSyntaxHighlighter.h"
-#include <LibGUI/JSSyntaxHighlighter.h>
 #include <LibGUI/TextEditor.h>
 #include <LibGfx/Palette.h>
 #include <LibJS/Lexer.h>
@@ -34,18 +33,17 @@ namespace Spreadsheet {
 
 void CellSyntaxHighlighter::rehighlight(Gfx::Palette palette)
 {
-    ASSERT(m_editor);
-    auto text = m_editor->text();
-    m_editor->document().spans().clear();
+    auto text = m_client->get_text();
+    m_client->spans().clear();
     if (!text.starts_with('=')) {
-        m_editor->update();
+        m_client->do_update();
         return;
     }
 
-    JSSyntaxHighlighter::rehighlight(palette);
+    JS::SyntaxHighlighter::rehighlight(palette);
 
     // Highlight the '='
-    m_editor->document().spans().empend(
+    m_client->spans().empend(
         GUI::TextRange { { 0, 0 }, { 0, 1 } },
         Gfx::TextAttributes {
             palette.syntax_keyword(),
@@ -59,7 +57,7 @@ void CellSyntaxHighlighter::rehighlight(Gfx::Palette palette)
     if (m_cell && m_cell->exception()) {
         auto range = m_cell->exception()->source_ranges().first();
         GUI::TextRange text_range { { range.start.line - 1, range.start.column }, { range.end.line - 1, range.end.column - 1 } };
-        m_editor->document().spans().prepend(
+        m_client->spans().prepend(
             GUI::TextDocumentSpan {
                 text_range,
                 Gfx::TextAttributes {
@@ -71,7 +69,7 @@ void CellSyntaxHighlighter::rehighlight(Gfx::Palette palette)
                 nullptr,
                 false });
     }
-    m_editor->update();
+    m_client->do_update();
 }
 
 CellSyntaxHighlighter::~CellSyntaxHighlighter()

Userland/Applications/Spreadsheet/CellSyntaxHighlighter.h

@@ -27,11 +27,11 @@
 #pragma once
 
 #include "Cell.h"
-#include <LibGUI/JSSyntaxHighlighter.h>
+#include <LibJS/SyntaxHighlighter.h>
 
 namespace Spreadsheet {
 
-class CellSyntaxHighlighter final : public GUI::JSSyntaxHighlighter {
+class CellSyntaxHighlighter final : public JS::SyntaxHighlighter {
 public:
     CellSyntaxHighlighter() { }
     virtual ~CellSyntaxHighlighter() override;

Userland/Applications/Spreadsheet/CellTypeDialog.cpp

@@ -36,7 +36,6 @@
 #include <LibGUI/ColorInput.h>
 #include <LibGUI/ComboBox.h>
 #include <LibGUI/ItemListModel.h>
-#include <LibGUI/JSSyntaxHighlighter.h>
 #include <LibGUI/Label.h>
 #include <LibGUI/ListView.h>
 #include <LibGUI/SpinBox.h>
@@ -44,6 +43,7 @@
 #include <LibGUI/TextEditor.h>
 #include <LibGUI/Widget.h>
 #include <LibGfx/FontDatabase.h>
+#include <LibJS/SyntaxHighlighter.h>
 
 REGISTER_WIDGET(Spreadsheet, ConditionsView);
 
@@ -425,7 +425,7 @@ ConditionView::ConditionView(ConditionalFormat& fmt)
         m_format.background_color = bg_input.color();
     };
 
-    formula_editor.set_syntax_highlighter(make<GUI::JSSyntaxHighlighter>());
+    formula_editor.set_syntax_highlighter(make<JS::SyntaxHighlighter>());
     formula_editor.set_should_hide_unnecessary_scrollbars(true);
     formula_editor.set_font(&Gfx::FontDatabase::default_fixed_width_font());
     formula_editor.on_change = [&] {

Userland/Applications/TextEditor/CMakeLists.txt

@@ -7,4 +7,4 @@ set(SOURCES
 )
 
 serenity_app(TextEditor ICON app-text-editor)
-target_link_libraries(TextEditor LibWeb LibMarkdown LibGUI LibShell LibRegex LibDesktop LibCpp)
+target_link_libraries(TextEditor LibWeb LibMarkdown LibGUI LibShell LibRegex LibDesktop LibCpp LibJS)

Userland/Applications/TextEditor/TextEditorWidget.cpp

@@ -43,7 +43,6 @@
 #include <LibGUI/FontPicker.h>
 #include <LibGUI/GMLSyntaxHighlighter.h>
 #include <LibGUI/INISyntaxHighlighter.h>
-#include <LibGUI/JSSyntaxHighlighter.h>
 #include <LibGUI/Menu.h>
 #include <LibGUI/MenuBar.h>
 #include <LibGUI/MessageBox.h>
@@ -57,6 +56,7 @@
 #include <LibGUI/ToolBarContainer.h>
 #include <LibGUI/VimEditingEngine.h>
 #include <LibGfx/Font.h>
+#include <LibJS/SyntaxHighlighter.h>
 #include <LibMarkdown/Document.h>
 #include <LibWeb/OutOfProcessWebView.h>
 #include <string.h>
@@ -476,7 +476,7 @@ TextEditorWidget::TextEditorWidget()
     syntax_menu.add_action(*m_cpp_highlight);
 
     m_js_highlight = GUI::Action::create_checkable("JavaScript", [&](auto&) {
-        m_editor->set_syntax_highlighter(make<GUI::JSSyntaxHighlighter>());
+        m_editor->set_syntax_highlighter(make<JS::SyntaxHighlighter>());
         m_editor->update();
     });
     syntax_actions.add_action(*m_js_highlight);

Userland/DevTools/HackStudio/Editor.cpp

@@ -38,12 +38,12 @@
 #include <LibGUI/Application.h>
 #include <LibGUI/GMLSyntaxHighlighter.h>
 #include <LibGUI/INISyntaxHighlighter.h>
-#include <LibGUI/JSSyntaxHighlighter.h>
 #include <LibGUI/Label.h>
 #include <LibGUI/Painter.h>
 #include <LibGUI/ScrollBar.h>
 #include <LibGUI/ShellSyntaxHighlighter.h>
 #include <LibGUI/Window.h>
+#include <LibJS/SyntaxHighlighter.h>
 #include <LibMarkdown/Document.h>
 #include <LibWeb/DOM/ElementFactory.h>
 #include <LibWeb/DOM/Text.h>
@@ -424,7 +424,7 @@ void Editor::set_document(GUI::TextDocument& doc)
         set_syntax_highlighter(make<GUI::GMLSyntaxHighlighter>());
         break;
     case Language::JavaScript:
-        set_syntax_highlighter(make<GUI::JSSyntaxHighlighter>());
+        set_syntax_highlighter(make<JS::SyntaxHighlighter>());
         break;
     case Language::Ini:
         set_syntax_highlighter(make<GUI::IniSyntaxHighlighter>());

Userland/Libraries/LibCpp/SyntaxHighlighter.cpp

@@ -77,8 +77,7 @@ bool SyntaxHighlighter::is_navigatable(void* token) const
 
 void SyntaxHighlighter::rehighlight(Gfx::Palette palette)
 {
-    ASSERT(m_editor);
-    auto text = m_editor->text();
+    auto text = m_client->get_text();
     Cpp::Lexer lexer(text);
     auto tokens = lexer.lex();
 
@@ -95,12 +94,12 @@ void SyntaxHighlighter::rehighlight(Gfx::Palette palette)
         span.data = reinterpret_cast<void*>(token.m_type);
         spans.append(span);
     }
-    m_editor->document().set_spans(spans);
+    m_client->do_set_spans(move(spans));
 
     m_has_brace_buddies = false;
     highlight_matching_token_pair();
 
-    m_editor->update();
+    m_client->do_update();
 }
 
 Vector<SyntaxHighlighter::MatchingTokenPair> SyntaxHighlighter::matching_token_pairs() const

Userland/Libraries/LibGUI/CMakeLists.txt

@@ -48,7 +48,6 @@ set(SOURCES
     IconView.cpp
     ImageWidget.cpp
     InputBox.cpp
-    JSSyntaxHighlighter.cpp
     JsonArrayModel.cpp
     Label.cpp
     Layout.cpp
@@ -109,4 +108,4 @@ set(GENERATED_SOURCES
 )
 
 serenity_lib(LibGUI gui)
-target_link_libraries(LibGUI LibCore LibGfx LibIPC LibThread LibShell LibRegex LibJS LibSyntax)
+target_link_libraries(LibGUI LibCore LibGfx LibIPC LibThread LibShell LibRegex LibSyntax)

Userland/Libraries/LibGUI/Forward.h

@@ -82,6 +82,7 @@ class TableView;
 class TextBox;
 class TextDocument;
 class TextDocumentLine;
+struct TextDocumentSpan;
 class TextDocumentUndoCommand;
 class TextEditor;
 class ThemeChangeEvent;

Userland/Libraries/LibGUI/GMLSyntaxHighlighter.cpp

@@ -32,7 +32,7 @@
 
 namespace GUI {
 
-static Syntax::TextStyle style_for_token_type(Gfx::Palette palette, GMLToken::Type type)
+static Syntax::TextStyle style_for_token_type(const Gfx::Palette& palette, GMLToken::Type type)
 {
     switch (type) {
     case GMLToken::Type::LeftCurly:
@@ -61,8 +61,7 @@ bool GMLSyntaxHighlighter::is_identifier(void* token) const
 
 void GMLSyntaxHighlighter::rehighlight(Gfx::Palette palette)
 {
-    ASSERT(m_editor);
-    auto text = m_editor->text();
+    auto text = m_client->get_text();
     GMLLexer lexer(text);
     auto tokens = lexer.lex();
 
@@ -78,12 +77,12 @@ void GMLSyntaxHighlighter::rehighlight(Gfx::Palette palette)
         span.data = reinterpret_cast<void*>(token.m_type);
         spans.append(span);
     }
-    m_editor->document().set_spans(spans);
+    m_client->do_set_spans(move(spans));
 
     m_has_brace_buddies = false;
     highlight_matching_token_pair();
 
-    m_editor->update();
+    m_client->do_update();
 }
 
 Vector<GMLSyntaxHighlighter::MatchingTokenPair> GMLSyntaxHighlighter::matching_token_pairs() const

Userland/Libraries/LibGUI/INISyntaxHighlighter.cpp

@@ -60,8 +60,7 @@ bool IniSyntaxHighlighter::is_identifier(void* token) const
 
 void IniSyntaxHighlighter::rehighlight(Gfx::Palette palette)
 {
-    ASSERT(m_editor);
-    auto text = m_editor->text();
+    auto text = m_client->get_text();
     IniLexer lexer(text);
     auto tokens = lexer.lex();
 
@@ -77,12 +76,12 @@ void IniSyntaxHighlighter::rehighlight(Gfx::Palette palette)
         span.data = reinterpret_cast<void*>(token.m_type);
         spans.append(span);
     }
-    m_editor->document().set_spans(spans);
+    m_client->do_set_spans(move(spans));
 
     m_has_brace_buddies = false;
     highlight_matching_token_pair();
 
-    m_editor->update();
+    m_client->do_update();
 }
 
 Vector<IniSyntaxHighlighter::MatchingTokenPair> IniSyntaxHighlighter::matching_token_pairs() const

Userland/Libraries/LibGUI/ShellSyntaxHighlighter.cpp

@@ -502,25 +502,24 @@ bool ShellSyntaxHighlighter::is_navigatable(void* token) const
 
 void ShellSyntaxHighlighter::rehighlight(Gfx::Palette palette)
 {
-    ASSERT(m_editor);
-    auto text = m_editor->text();
+    auto text = m_client->get_text();
 
     Parser parser(text);
     auto ast = parser.parse();
 
     Vector<GUI::TextDocumentSpan> spans;
     GUI::TextPosition position { 0, 0 };
-    HighlightVisitor visitor { spans, palette, m_editor->document() };
+    HighlightVisitor visitor { spans, palette, m_client->get_document() };
 
     if (ast)
         ast->visit(visitor);
 
     quick_sort(spans, [](auto& a, auto& b) { return a.range.start() < b.range.start(); });
 
-    m_editor->document().set_spans(spans);
+    m_client->do_set_spans(move(spans));
     m_has_brace_buddies = false;
     highlight_matching_token_pair();
-    m_editor->update();
+    m_client->do_update();
 }
 
 Vector<Syntax::Highlighter::MatchingTokenPair> ShellSyntaxHighlighter::matching_token_pairs() const

Userland/Libraries/LibGUI/TextDocument.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -79,7 +79,7 @@ public:
     const TextDocumentLine& line(size_t line_index) const { return m_lines[line_index]; }
     TextDocumentLine& line(size_t line_index) { return m_lines[line_index]; }
 
-    void set_spans(const Vector<TextDocumentSpan>& spans) { m_spans = spans; }
+    void set_spans(Vector<TextDocumentSpan> spans) { m_spans = move(spans); }
 
     void set_text(const StringView&);
 

Userland/Libraries/LibGUI/TextEditor.h

@@ -37,13 +37,15 @@
 #include <LibGUI/TextRange.h>
 #include <LibGfx/TextAlignment.h>
 #include <LibSyntax/Forward.h>
+#include <LibSyntax/HighlighterClient.h>
 
 namespace GUI {
 
 class TextEditor
     : public ScrollableWidget
-    , public TextDocument::Client {
-    C_OBJECT(TextEditor)
+    , public TextDocument::Client
+    , public Syntax::HighlighterClient {
+    C_OBJECT(TextEditor);
 
 public:
     enum Type {
@@ -241,6 +243,16 @@ private:
     virtual void document_did_set_text() override;
     virtual void document_did_set_cursor(const TextPosition&) override;
 
+    // ^Syntax::HighlighterClient
+    virtual Vector<TextDocumentSpan>& spans() final { return document().spans(); }
+    virtual const Vector<TextDocumentSpan>& spans() const final { return document().spans(); }
+    virtual void highlighter_did_set_spans(Vector<TextDocumentSpan> spans) { document().set_spans(move(spans)); }
+    virtual void set_span_at_index(size_t index, TextDocumentSpan span) final { document().set_span_at_index(index, move(span)); }
+    virtual void highlighter_did_request_update() final { update(); }
+    virtual String highlighter_did_request_text() const final { return text(); }
+    virtual GUI::TextDocument& highlighter_did_request_document() final { return document(); }
+    virtual GUI::TextPosition highlighter_did_request_cursor() const final { return m_cursor; }
+
     void create_actions();
     void paint_ruler(Painter&);
     void update_content_size();

Userland/Libraries/LibJS/CMakeLists.txt

@@ -81,8 +81,9 @@ set(SOURCES
     Runtime/VM.cpp
     Runtime/Value.cpp
     Runtime/WithScope.cpp
+    SyntaxHighlighter.cpp
     Token.cpp
 )
 
 serenity_lib(LibJS js)
-target_link_libraries(LibJS LibM LibCore LibCrypto LibRegex)
+target_link_libraries(LibJS LibM LibCore LibCrypto LibRegex LibSyntax)

Userland/Libraries/LibJS/SyntaxHighlighter.cpp

@@ -25,16 +25,16 @@
  */
 
 #include <AK/Debug.h>
-#include <LibGUI/JSSyntaxHighlighter.h>
 #include <LibGUI/TextEditor.h>
 #include <LibGfx/Font.h>
 #include <LibGfx/Palette.h>
 #include <LibJS/Lexer.h>
+#include <LibJS/SyntaxHighlighter.h>
 #include <LibJS/Token.h>
 
-namespace GUI {
+namespace JS {
 
-static Syntax::TextStyle style_for_token_type(Gfx::Palette palette, JS::TokenType type)
+static Syntax::TextStyle style_for_token_type(const Gfx::Palette& palette, JS::TokenType type)
 {
     switch (JS::Token::category(type)) {
     case JS::TokenCategory::Invalid:
@@ -58,21 +58,20 @@ static Syntax::TextStyle style_for_token_type(Gfx::Palette palette, JS::TokenTyp
     }
 }
 
-bool JSSyntaxHighlighter::is_identifier(void* token) const
+bool SyntaxHighlighter::is_identifier(void* token) const
 {
     auto js_token = static_cast<JS::TokenType>(reinterpret_cast<size_t>(token));
     return js_token == JS::TokenType::Identifier;
 }
 
-bool JSSyntaxHighlighter::is_navigatable([[maybe_unused]] void* token) const
+bool SyntaxHighlighter::is_navigatable([[maybe_unused]] void* token) const
 {
     return false;
 }
 
-void JSSyntaxHighlighter::rehighlight(Gfx::Palette palette)
+void SyntaxHighlighter::rehighlight(Gfx::Palette palette)
 {
-    ASSERT(m_editor);
-    auto text = m_editor->text();
+    auto text = m_client->get_text();
 
     JS::Lexer lexer(text);
 
@@ -125,15 +124,15 @@ void JSSyntaxHighlighter::rehighlight(Gfx::Palette palette)
             was_eof = true;
     }
 
-    m_editor->document().set_spans(spans);
+    m_client->do_set_spans(move(spans));
 
     m_has_brace_buddies = false;
     highlight_matching_token_pair();
 
-    m_editor->update();
+    m_client->do_update();
 }
 
-Vector<Syntax::Highlighter::MatchingTokenPair> JSSyntaxHighlighter::matching_token_pairs() const
+Vector<Syntax::Highlighter::MatchingTokenPair> SyntaxHighlighter::matching_token_pairs() const
 {
     static Vector<Syntax::Highlighter::MatchingTokenPair> pairs;
     if (pairs.is_empty()) {
@@ -144,12 +143,12 @@ Vector<Syntax::Highlighter::MatchingTokenPair> JSSyntaxHighlighter::matching_tok
     return pairs;
 }
 
-bool JSSyntaxHighlighter::token_types_equal(void* token1, void* token2) const
+bool SyntaxHighlighter::token_types_equal(void* token1, void* token2) const
 {
     return static_cast<JS::TokenType>(reinterpret_cast<size_t>(token1)) == static_cast<JS::TokenType>(reinterpret_cast<size_t>(token2));
 }
 
-JSSyntaxHighlighter::~JSSyntaxHighlighter()
+SyntaxHighlighter::~SyntaxHighlighter()
 {
 }
 

Userland/Libraries/LibJS/SyntaxHighlighter.h

@@ -28,12 +28,12 @@
 
 #include <LibSyntax/Highlighter.h>
 
-namespace GUI {
+namespace JS {
 
-class JSSyntaxHighlighter : public Syntax::Highlighter {
+class SyntaxHighlighter : public Syntax::Highlighter {
 public:
-    JSSyntaxHighlighter() { }
-    virtual ~JSSyntaxHighlighter() override;
+    SyntaxHighlighter() { }
+    virtual ~SyntaxHighlighter() override;
 
     virtual bool is_identifier(void*) const override;
     virtual bool is_navigatable(void*) const override;

Userland/Libraries/LibSyntax/Forward.h

@@ -29,5 +29,6 @@
 namespace Syntax {
 
 class Highlighter;
+class HighlighterClient;
 
 }

Userland/Libraries/LibSyntax/Highlighter.cpp

@@ -25,6 +25,7 @@
  */
 
 #include <LibGUI/TextEditor.h>
+#include <LibGfx/Color.h>
 #include <LibSyntax/Highlighter.h>
 
 namespace Syntax {
@@ -35,8 +36,7 @@ Highlighter::~Highlighter()
 
 void Highlighter::highlight_matching_token_pair()
 {
-    ASSERT(m_editor);
-    auto& document = m_editor->document();
+    auto& document = m_client->get_document();
 
     enum class Direction {
         Forward,
@@ -93,7 +93,7 @@ void Highlighter::highlight_matching_token_pair()
         buddy1.attributes.background_color = Color::DarkCyan;
         buddy0.attributes.color = Color::White;
         buddy1.attributes.color = Color::White;
-        m_editor->update();
+        m_client->do_update();
     };
 
     auto pairs = matching_token_pairs();
@@ -103,7 +103,7 @@ void Highlighter::highlight_matching_token_pair()
         auto token_type = span.data;
 
         for (auto& pair : pairs) {
-            if (token_types_equal(token_type, pair.open) && span.range.start() == m_editor->cursor()) {
+            if (token_types_equal(token_type, pair.open) && span.range.start() == m_client->get_cursor()) {
                 auto buddy = find_span_of_type(i, pair.close, pair.open, Direction::Forward);
                 if (buddy.has_value())
                     make_buddies(i, buddy.value());
@@ -115,7 +115,7 @@ void Highlighter::highlight_matching_token_pair()
         right_of_end.set_column(right_of_end.column() + 1);
 
         for (auto& pair : pairs) {
-            if (token_types_equal(token_type, pair.close) && right_of_end == m_editor->cursor()) {
+            if (token_types_equal(token_type, pair.close) && right_of_end == m_client->get_cursor()) {
                 auto buddy = find_span_of_type(i, pair.open, pair.close, Direction::Backward);
                 if (buddy.has_value())
                     make_buddies(i, buddy.value());
@@ -125,29 +125,27 @@ void Highlighter::highlight_matching_token_pair()
     }
 }
 
-void Highlighter::attach(GUI::TextEditor& editor)
+void Highlighter::attach(HighlighterClient& client)
 {
-    ASSERT(!m_editor);
-    m_editor = editor;
+    ASSERT(!m_client);
+    m_client = &client;
 }
 
 void Highlighter::detach()
 {
-    ASSERT(m_editor);
-    m_editor = nullptr;
+    m_client = nullptr;
 }
 
 void Highlighter::cursor_did_change()
 {
-    ASSERT(m_editor);
-    auto& document = m_editor->document();
+    auto& document = m_client->get_document();
     if (m_has_brace_buddies) {
         if (m_brace_buddies[0].index >= 0 && m_brace_buddies[0].index < static_cast<int>(document.spans().size()))
             document.set_span_at_index(m_brace_buddies[0].index, m_brace_buddies[0].span_backup);
         if (m_brace_buddies[1].index >= 0 && m_brace_buddies[1].index < static_cast<int>(document.spans().size()))
             document.set_span_at_index(m_brace_buddies[1].index, m_brace_buddies[1].span_backup);
         m_has_brace_buddies = false;
-        m_editor->update();
+        m_client->do_update();
     }
     highlight_matching_token_pair();
 }

Userland/Libraries/LibSyntax/Highlighter.h

@@ -30,6 +30,7 @@
 #include <AK/WeakPtr.h>
 #include <LibGUI/TextDocument.h>
 #include <LibGfx/Palette.h>
+#include <LibSyntax/HighlighterClient.h>
 
 namespace Syntax {
 
@@ -61,14 +62,15 @@ public:
     virtual bool is_identifier(void*) const { return false; };
     virtual bool is_navigatable(void*) const { return false; };
 
-    void attach(GUI::TextEditor& editor);
+    void attach(HighlighterClient&);
     void detach();
     void cursor_did_change();
 
 protected:
     Highlighter() { }
 
-    WeakPtr<GUI::TextEditor> m_editor;
+    // FIXME: This should be WeakPtr somehow
+    HighlighterClient* m_client { nullptr };
 
     struct MatchingTokenPair {
         void* open;

Userland/Libraries/LibSyntax/HighlighterClient.h

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibGUI/Forward.h>
+
+namespace Syntax {
+
+class HighlighterClient {
+public:
+    virtual ~HighlighterClient() = default;
+
+    virtual Vector<GUI::TextDocumentSpan>& spans() = 0;
+    virtual const Vector<GUI::TextDocumentSpan>& spans() const = 0;
+    virtual void set_span_at_index(size_t index, GUI::TextDocumentSpan span) = 0;
+
+    virtual String highlighter_did_request_text() const = 0;
+    virtual void highlighter_did_request_update() = 0;
+    virtual GUI::TextDocument& highlighter_did_request_document() = 0;
+    virtual GUI::TextPosition highlighter_did_request_cursor() const = 0;
+    virtual void highlighter_did_set_spans(Vector<GUI::TextDocumentSpan>) = 0;
+
+    void do_set_spans(Vector<GUI::TextDocumentSpan> spans) { highlighter_did_set_spans(move(spans)); }
+    void do_update() { highlighter_did_request_update(); }
+
+    String get_text() const { return highlighter_did_request_text(); }
+    GUI::TextDocument& get_document() { return highlighter_did_request_document(); }
+    GUI::TextPosition get_cursor() const { return highlighter_did_request_cursor(); }
+};
+
+}