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/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(); }
+};
+
+}