LibGUI: Introduce GML - a simple GUI Markup Language :^)

This patch replaces the UI-from-JSON mechanism with a more
human-friendly DSL.

The current implementation simply converts the GML into a JSON object
that can be consumed by GUI::Widget::load_from_json(). The parser is
not very helpful if you make a mistake.

The language offers a very simple way to instantiate any registered
Core::Object class by simply saying @ClassName

@GUI::Label {
    text: "Hello friends!"
    tooltip: ":^)"
}

Layouts are Core::Objects and can be assigned to the "layout" property:

@GUI::Widget {
    layout: @GUI::VerticalBoxLayout {
        spacing: 2
        margins: [8, 8, 8, 8]
    }
}

And finally, child objects are simply nested within their parent:

@GUI::Widget {
    layout: @GUI::HorizontalBoxLayout {
    }
    @GUI::Button {
        text: "OK"
    }
    @GUI::Button {
        text: "Cancel"
    }
}

This feels a *lot* more pleasant to write than the JSON we had. The fact
that no new code was being written with the JSON mechanism was pretty
telling, so let's approach this with developer convenience in mind. :^)

1 files changed, 2 insertions, 2 deletions

diff --git a/Applications/Browser/main.cpp b/Applications/Browser/main.cpp
index 7fe4e5f94d..3624ca6076 100644
--- a/Applications/Browser/main.cpp
+++ b/Applications/Browser/main.cpp
@@ -30,7 +30,7 @@
 #include "Tab.h"
 #include "WindowActions.h"
 #include <AK/StringBuilder.h>
-#include <Applications/Browser/BrowserWindowUI.h>
+#include <Applications/Browser/BrowserWindowGML.h>
 #include <LibCore/ArgsParser.h>
 #include <LibCore/ConfigFile.h>
 #include <LibCore/File.h>
@@ -138,7 +138,7 @@ int main(int argc, char** argv)
     window->set_title("Browser");
 
     auto& widget = window->set_main_widget<GUI::Widget>();
-    widget.load_from_json(browser_window_ui_json);
+    widget.load_from_gml(browser_window_gml);
 
     auto& tab_widget = static_cast<GUI::TabWidget&>(*widget.find_descendant_by_name("tab_widget"));