Introduction to offline content apps

UI structure + UI theme + content = app.

The structure is written in terms of modular UI blocks (see below) assembled in a declarative UI file. This declarative file is a JSON file. However, we include a preprocessor tool called Autobahn so that you can write your app description in a more expressive, human-friendly YAML format. See data/preset/*.yaml for examples.

The theme is a GTK CSS file. We suggest writing themes using SCSS and then compiling them down to regular CSS. We provide SCSS modules that your SCSS code can import; see data/css/.

The content is in the form of a shard file; see eos-shard for more information. We are working on tools that allow you to build shard files easily on your own machine. For now, you can include the --dummy-content option when running an app and it will load with sample content.

Modular UI blocks

UI modules are GObjects, with a few extra features and a few restrictions. They are meant to be assembled in a declarative file, without writing having to write any code such as signal handlers.

First of all, UI modules do not emit signals, because their behavior is part of their implementation, and UI descriptions are purely declarative: no code. All properties accessible from the declarative file are treated as construct-only (except when using property bindings.) Modules have slots and references, which are named spots where other modules can be contained or referenced.

Here are the types of UI modules and how they fit together. See js/app/modules/ for the code.

  • Arrangement - These modules generally have a card slot which a Card can go into. They arrange a set of dynamically created cards on the screen.
  • Banner - These modules represent a piece of data which is presented to the user, such as an app’s logo or a search term.
  • Card - These modules represent a document in the database of offline content, but are not a full View of the document. They display its metadata (title, keywords) in various ways.
  • ContentGroup - This is the heart of displaying offline content. Content groups have selection and arrangement slots. They make sure the Arrangement receives (and creates Cards for) the records that the Selection wants to display.
  • Controller - These modules define different types of app experiences. They are in charge of what happens when you click somewhere.
  • Decoration - These modules are UI elements which are used for display only.
  • Filter - These modules can be added to a Selection to display only some of its records.
  • Layout - These modules contain submodules and arrange them on one page of the app.
  • Navigation - These modules are UI elements which are used for navigation through an app.
  • Order - These modules can be added to a Selection to change the sorting order in which its records are displayed.
  • Pager - Modules can also act as pages of an app, like pages in a website. Pager modules contain submodules and display them one at a time, with optional animations between them.
  • Selection - These modules retrieve content records from the offline content database. A Selection serves records through a ContentGroup to an Arrangement, which turns the records into Cards.
  • View - These modules display the actual content.
  • Window - These modules are the toplevel windows which contain other modules.

Here’s a diagram of what contains what:

        (more) Layout