In this page I will try to explain in an extremely basic form the functions of the
components of an application for KaiOS / Firefox OS:
KaiOS is based on Firefox OS and as such it supports applications in HTML,
JavaScript, and CSS. Just like the current webpages that we have get used to using on a daily
basis. We can see in certain respects KaiOS as a browser transformed into an operating system.
The name Boot2Gecko or B2G suggests that in fact the engine is
Gekco used in all versions of Firefox
prior to 57. When you open Settings app and look in the "tab" more information, you can see
the platform is 48.0a2. This confirms the hypothesis that in reality it is a browser,
Firefox 48, as also suggested by certain webpages that we explore, identifying ourselves
with the Mozilla's browser.
Having said that we can assume that the applications we are using are nothing more than the
tabs of the navigation of a normal browser. This also makes us understand that any website
can become a webapp. So being able to move a website offline on your device makes it a full
fledged webapp.
The HTML file is the central nervous system of an application. In it all elements that
are part of that page are connected. In other words, all elements which make
parameter, launch_path which requires an HTML file(usually named index.html) in the
specified path (usually in the main folder/directory) and in which the functions and calls
to the individual components of the application are indexed. Using this rule you know how
to start with the structure.
CSS lists the styles and the rendering of the page and its verious HTML elements that
will be displayed to the final user. Basically it is the GUI of the application and sometimes
is not needed for more simple and basic applications(it can be replaced from pictures).
Javascript or JS is practically the musculoskeletal system of the application, and
is used to make all elements move according to the instructions provided inside them. It really
is the workforce of the application.
The Manifest is the heart and lymphatic system of the application. It contains instructions
for moving the whole structure of the "webpage". Without it the application has no "life".
The permissions field in the app manifest
controls the app's access to various sensitive APIs on the device(sometimes called Web APIs).
Apps based on the permissions they have are in 3 groups:
Web apps: These only have a basic level of permissions and don't have access to privileged
or internal APIs.
Privileged apps: These have all permissions of web apps and more.
Hosted apps
can't be privileged apps and they must be packaged apps.
Internal (certified) apps: These have all permissions of privileged and web apps plus more.
Certified/internal apps can only be installed on a device by Mozilla or a device vendor;
not third party developers.
For more information on app types, see Types of packaged apps
(source http://developer.mozilla.org/)
As we have seen, to start an offline app we have to set an HTML file in launch_path.
To start an hosted app it's sufficient the manifest.webappfile, in wich you have to
replace the launch_path line with a start_url, that requires the link of the website
(EXAMPLE1).
That said, this idea that I suggested to you should guarantee more courage to those
who want to start at a more advanced level for the first time, which is the compilation
of the aforementioned files (for the OmniSD zip package format take a look to the
EXAMPLES 2 and 3 at the end of this page).
Related video: https://youtu.be/NlGlam9edgQ
OmniSD accepts app packages in the ZIP format. An archive must contain three files:
application.zip: The file with the actual WebIDE compatible KaiOS/FFOS app.metadata.json: This file should be in the following format:{
"version": 1,
"manifestURL": "app://[your_app_id_here]/manifest.webapp"
}
where [your_app_id] has to be replaced with the actual ID (origin) of your app registered
in the manifest, and manifest.webapp has to be renamed if it is called differently in
application.zip archive. The version number "version": 1, must be always 1.
Other than that, the application structure in application.zip must
match the general KaiOS and Firefox OS app structure.
── myapp.zip
├── application.zip
│ ├── index.html
│ └── manifest.webapp
└── metadata.json
See http://developer.kaiostech.com for more details.
Related video: https://youtu.be/eTrcJh3Dt0A
Some models are ready to be downloaded and completed by you (you can find the
links that refer to video tutorials in the description):
Example 1: Webwrapper or hosted app, simple, lightweight with cursor function
but not a complete app. It needs to work online. Here's a video tutorial
on how it works.
Example 2: Shortcut, this opens a website using the built in browser.
It includes a Javascript file (main.js) that will be called from the index.html file,
that is called from the "launch_path" of the manifest.webapp file. This is a basic
example to start learning about Javascript and starting to create an offline app.
A video tutorial.
Example 3: Offline, This is a basic structure (empty enough!) to
complete with a complete app to make it work on OmniSD. A
video tutorial.