DevTools: Add a simple GML Playground application :^)

This app allows you to edit GML and see the results live. Pretty cool!

DevTools/CMakeLists.txt

@@ -1,4 +1,5 @@
 add_subdirectory(HackStudio)
 add_subdirectory(Inspector)
+add_subdirectory(Playground)
 add_subdirectory(Profiler)
 add_subdirectory(UserspaceEmulator)

DevTools/Playground/CMakeLists.txt

@@ -0,0 +1,6 @@
+set(SOURCES
+    main.cpp
+)
+
+serenity_app(Playground)
+target_link_libraries(Playground LibGUI)

DevTools/Playground/main.cpp

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2020, 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.
+ */
+
+#include <LibGUI/Application.h>
+#include <LibGUI/GMLSyntaxHighlighter.h>
+#include <LibGUI/Splitter.h>
+#include <LibGUI/TextEditor.h>
+#include <LibGUI/Window.h>
+
+int main(int argc, char** argv)
+{
+    auto app = GUI::Application::construct(argc, argv);
+    auto window = GUI::Window::construct();
+    window->set_title("GML Playground");
+    window->resize(800, 600);
+
+    auto& splitter = window->set_main_widget<GUI::HorizontalSplitter>();
+
+    auto& editor = splitter.add<GUI::TextEditor>();
+    auto& preview = splitter.add<GUI::Widget>();
+
+    editor.set_syntax_highlighter(make<GUI::GMLSyntaxHighlighter>());
+    editor.set_automatic_indentation_enabled(true);
+
+    editor.on_change = [&] {
+        // FIXME: This is not a very expressive way to remove all children..
+        while (!preview.children().is_empty())
+            preview.children().first().remove_from_parent();
+
+        preview.load_from_gml(editor.text());
+    };
+
+    window->show();
+    return app->exec();
+}