How to use C libraries to create GNOME app in JavaScript

Question

I am a beginner in GNOME desktop application development so I am trying to learn about it as much as possible. I have read various tutorials present on developer.gnome.org written for JavaScript. I know that through GObject Introspection I can access C libraries in JavaScript.

As use of JavaScript for desktop applications is new so not many documentations are present. I was wondering if there is any way I can know which functions I can use with what parameters to access some libraries.

For example I can create a button using GTK in JavaScript by:

this.mybutton = new GTK.Button({some code here});

How can I come to know about the name of the functions I can use? Is there any way I can make out the name of the function for JavaScript seeing the documentation written for C?

For some of the libraries I have seen this documentation written for JavaScript. Any help will be appreciated to understand more about GNOME application development.

My first instinct is to say, if you know javascript, you almost know C, so just use C. For the next person who tries to help, here's a link to a hello world in JS just to show that javascript for gnome apps is possible: https://developer.gnome.org/gnome-devel-demos/3.7/helloWorld.js.html.en — Tom Cerul, Mar 19 '14 at 15:27
@TomCerul yes i know C but i want to learn to create apps in javascript and wanted to know how can i use C libraries in javascript. How can i know about the function names and parameters which i can use? — prolific, Mar 19 '14 at 15:39

score 5 · Answer 1 · answered Mar 24 '14 at 22:06

I agree with you: the documentation is pretty low on the subject.
Most of the time I try to find already written code from other developers and change it to have what I want.
The C documentation is pretty complete on http://developer.gnome.org and most of the time you can use nearly the same methods.
I suggest you to take a look at this web site: http://www.roojs.org/seed/gir-1.2-gtk-3.0/seed/
And also to this one: http://zetcode.com/gui/javascriptgtktutorial/
Good luck with your javascript development !!!

user.dz · Answer 2 · 2021-10-30T17:53:17.657

There is new host for Gnome GJS documentation:

https://gjs.guide/
https://gjs-docs.gnome.org/ for API's

You still can get Javascript function mapped to the that C library function by searching though GIR files. Each library should have an XML file containing introspection information.

Example from one question I asked before.

grep -rn gdk_keymap_get_default /usr/share/gir-1.0/

/usr/share/gir-1.0/Gdk-2.0.gir:16781:                c:identifier="gdk_keymap_get_default"
/usr/share/gir-1.0/Gdk-3.0.gir:15776:      <function name="get_default" c:identifier="gdk_keymap_get_default">

vim /usr/share/gir-1.0/Gdk-3.0.gir +15776

    <class name="Keymap"
           c:symbol-prefix="keymap"
           c:type="GdkKeymap"
           parent="GObject.Object"
           glib:type-name="GdkKeymap"
           glib:get-type="gdk_keymap_get_type">
      <doc xml:space="preserve">A #GdkKeymap defines the translation from keyboard state
(including a hardware key, a modifier mask, and active keyboard group)
to a keyval. This translation has two phases. The first phase is
to determine the effective keyboard group and level for the keyboard
state; the second phase is to look up the keycode/group/level triplet
in the keymap and see what keyval it corresponds to.</doc>
      <function name="get_default" c:identifier="gdk_keymap_get_default">
        <doc xml:space="preserve">Returns the #GdkKeymap attached to the default display.</doc>
        <return-value transfer-ownership="none">
          <doc xml:space="preserve">the #GdkKeymap attached to the default display.</doc>
          <type name="Keymap" c:type="GdkKeymap*"/>
        </return-value>
      </function>

How to use C libraries to create GNOME app in JavaScript

2 Answers2