shadow-cljs-gjs-target

This project implements a build target for shadow-cljs so that Clojurescript can be compiled to Javascript in a form suitable for Gnome Javascript Bindings - Gjs.

Notes

• This is a modification of the :node-script target from original shadow-cljs source code.
• Only development mode compilation works.
• Gjs does not have a console object. As such, a rudimentary console analog is implemented which proxies appropriate functions in Gjs. This makes Clojurescript println and related functions working as is.
• Gjs builtin modules(i.e. gi.Gtk, system) are importable as Clojurescript namespaces using a special syntax.

Special syntax for importing builtin modules

Gjs builtin modules can be accessed using a string based namespace syntax - "gjs.<builtin-module-name>". For example, if you want to import the gi.Gtk module, the mapped namespace name should be "gjs.gi.Gtk".

Import syntax mapping

Javascript	Clojurescript
const Gtk = imports.gi.Gtk;	(require '["gjs.gi.Gtk" :as Gtk])
const ByteArray = imports.ByteArray;	(require '["gjs.byteArray" :as ByteArray])
const { Gtk, GLib } = imports.gi;	(require '["gjs.gi" :refer [Gtk GLib]])

Tutorial

Here's a short tutorial on how to get a simple Gtk app and running with Clojurescript. Note that I am detailing the lowest friction way of installing and using shadow-cljs. Feel free to use lein, boot or deps.edn, if you want so. Look at shadow-cljs documentation to know how to do that.

• Install npm with your distribution's package manager. Also, don't forget to install gjs and gobject introspection bindings, which is packaged under name gir1.2-javascriptcoregtk-4.0 in Ubuntu 20.04.
• Create a demo shadow cljs project with npx create-cljs-project gjs-demo. This should create a project directory named gjs-demo. Change current directory to it.
• Create a file named gjs_demo.cljs under directory src/main/ with the following content -

(ns gjs-demo
    (:require [clojure.string :as str]
              ["gjs.gi.Gtk" :as Gtk]
              ["gjs.system" :as system]))

(defn ^:export main [& args]
  (println "Hello from console!")
  (println "Command line arguments are: " (str/join ", " args))
  (let [msg (str "Hello, Gtk + Clojurescript!\ngjs version = "
                 (.-version system))]
        (Gtk/init nil)
        (let [win   (Gtk/Window.)
              label (Gtk/Label. #js {:label msg})]
            (doto win
              (.set_size_request 400 150)
              (.connect "delete-event" (fn [] (Gtk/main_quit)))
              (.add label)
              (.show_all))
            (Gtk/main))))

• Edit the shadow-cljs.edn file. Change it's content to -

;; shadow-cljs configuration
{:source-paths
 ["src/dev"
  "src/main"
  "src/test"]

 :dependencies
 [[titonbarua/shadow-cljs-gjs-target "0.1.0"]]

 :builds
 {:app {:target shadow-cljs-gjs-target.core
        :output-dir "./jslibs"
        :output-to "./app.js"
        :main gjs-demo/main}}}

• Run npx shadow-cljs compile app. This should emit a development javascript file named app.js at project root. Run it with gjs app.js. If everything is ok, you should see a tiny Gtk window with some text.

• To produce a release build, run npx shadow-cljs release.

More Examples

Take a look at examples directory for more robust usage examples. You can compile them by running the relevant compile.sh script.

Screenshots

Related resources

• Gjs guides
• Gjs Javascript examples
• Gjs project documentation
• Shadow-cljs User Manual

Things to TODO:

• Fix release mode compilation.
• Source maps don't work.
• REPL does not work.
• There needs to be a way to explicitly set gi versions before import, like: imports.gi.versions.Gtk = "3.0";
• Needs to add tests.
• Take care of undefined property errors.

License

Copyright © 2020 Titon Barua

This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which is available at http://www.eclipse.org/legal/epl-2.0.

This Source Code may also be made available under the following Secondary Licenses when the conditions for such availability set forth in the Eclipse Public License, v. 2.0 are satisfied: GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version, with the GNU Classpath Exception which is available at https://www.gnu.org/software/classpath/license.html.