Currently there are multiple libraries planned to be integrated deeply into linux: Gtk, WebkitGTK, Libchamplain, libhandy, GIO, gstreamer.
Note: As the project is still in early development not all features mentioned below must be available: Refactorings can remove previous available features.
Gtk is the toolkit which is used to display windows and widgets on the screen. The widgets can be added directly in code or described through an xml file.
Supported widgets are for example: Windows, dialogs, lables, images, spinner, progressbars, several buttons and switches, textboxes, tables, lists, menus, toolbars, popovers, and much more. It powers several linux desktops like Gnome and Xfce and applications like Gimp.
WebkitGTK is a browser component for GTK and can be used to embed the webkit webengine into an application as a widget. There is support for the web inspector and several settings to tweak the webview to your needs.
The bindings make it easy to:
Libchamplain is map component for GTK and can be used to embed maps into an application widget. By default it uses openstreetmap.
libhandy extends GTK with new widgets, to support mobile devices. Meaning full blown applications automatically adopt their UI to different view modes,if the available space changes.
One widget of this library is the Paginator which is shown in the pictures above. It allows to swipe through widgets and is used to switch between the webpage and maps control.
GIO is a library to allow easy access to input / output operations. Currently there is initial support for DBus operations. DBus is a standardized IPC-Framework which all major linux desktops use for interprocess communication.
Gstreamer is a multimedia library to play back various media format via a flexible pipelining system. The code to playback a movie is in the samples. (Homepage of the free movie: https://mango.blender.org/)