Overview

Genero Web Application (GWA) is a browser-based solution that combines Genero Browser Client, p-code modules, and a WebAssembly-based runtime for executing applications offline as progressive web apps. It supports full Genero GUI features, requires HTTPS for secure deployment, and is ideal for scalable use cases, including offline functionality and large user bases.

The GWA is an end-to-end web application solution that bundles together a Genero Browser Client, Genero p-code modules (42m), a Genero VM, and resources into a single page application (SPA).

The GWA ships a WebAssembly (external link) (wasm) version of the VM for your application — a format that enables deployment on the web and execution of the application in a browser. Like on desktop, this VM interprets .42m p-code modules.

The VM is created with the help of the emscripten (external link) compiler that is bundled with each GWA application. The processing speed is almost as fast on the browser as native code on the desktop.

With a GWA application, you do not need a runtime system (fglrun) process on the server side. In fact, there is no other software server side except a web server. A GWA application is by default a "progressive web app" (PWA); meaning once loaded from a web server, it can continue to run offline without any connection to the internet.

All GUI features available in the Genero Browser Client are fully supported in a GWA application, so Genero forms and styles run as usual together with Genero interaction statements such as INPUT/INPUT ARRAY/CONSTRUCT/MENU/DIALOG, and so on.

A GWA application has certain similarities with Genero Mobile for Android™(GMA) and Genero Mobile for iOS (GMI) application; however, the main difference is that the Genero runtime is not compiled into native code, instead the runtime system is compiled to WebAssembly (external link) modules (wasm) for execution on the browser.

Another noticeable difference between GMA/GMI and GWA, is that a GWA application emulates a file system in the browser, whereas in a GMA/GMI application the file systems of Android/IOS® can be used.

Prerequisites

GWA has requirements for delivering applications in a secure context (external link) as defined by the W3C consortium:
  • The GWA uses Service Workers that require you to run applications with HTTPS activated, or to use localhost. Even if in development localhost (http://localhost or http://127.0.0.1) can be used, it is mainly necessary to develop with HTTPS activated. Of course, in production, HTTPS is mandatory.
  • It is recommended to only use X.509 certificates issued by a recognized certificate authority, such as Let's Encrypt, in both development and in production.
    Note: Self-signed certificates

    It is possible to use self-signed certificates for development as long as your browser allows the usage of those certificates.

GWA use cases

The following are examples of some common GWA use cases:

  • Run application from a URL: Build a GWA application like you would a mobile application for GMI/GMA except with the advantage that you do not have to managed it through App Store; the installation is an ordinary web URL. Once the URL is selected by the end user, the application is downloaded, starts immediately, and is also immediately available for offline use.
  • Launch from mobile home screen icon: For mobiles with Chrome/Edge browsers, an installation menu appears, prompting the end user to save this application under a mobile home screen icon. Starting the application from this icon does not require an internet connection. With other browsers, users can bookmark the application with the same offline functionality. In IOS Safari® for example, add to home screen.
  • Launch from desktop icon: For desktops with Chrome/Edge browsers, an install button appears in the address bar, which allows the user to save the application to a desktop icon, turning the application into a desktop application with offline functionality.
  • Facilitate large numbers of simultaneous end users: GWA applications are the medium of choice when it comes to giving access to large number of simultaneous end users. Standard Genero desktop applications are server based and scale well up to 1000 and even more end users, but if the potential simultaneous end user count is much higher (for example, 100,000 or more) then it is time to switch to GWA architecture – with web services server side and the program logic running entirely client side.
  • Create GWA applications written in Genero BDL: This is typically the case for a GWA application: code written entirely in Genero runs client side, communication with the server is done via Genero com API/REST services. GWA applications can therefore compete with other client-side JavaScript technologies; with the added advantage that you can code your applications in Genero BDL.

Recommendations for use of Genero Web application

GWA has these best practice recommendations:

  • Install the GWA and the REST services on the same host: As GWA is actually a web application running in a browser, you can only communicate via REST web services to exchange data with a third party server. Therefore, we recommend you install the GWA and the REST services on the same host and port; otherwise, you may face a lot of Cross-Origin Resource Sharing (CORS) issues.
  • Set CORS headers on external servers providing web services: If you need to access another REST service located on another host and port machine, and if the REST requests are basic – simple GET or x-WWW-form-urlencoded type requests – you will have to set the following CORS header in the second host machine: Access-Control-Allow-Origin:"https://host:port"