First, grab a coffee and spend 32 entertaining minutes with Theo.

Ok, now that you have enjoyed his sartorial stylings, lets talk about WebSockets and avoiding JavaScript.

We have been experimenting with WebSockets and the HTMLRenderer. The goal is to see if it is possible to build a highly interactive desktop app with almost no JavaScript, where every UI interaction is handled by APL. This appears to work, and be a viable approach. We have implemented a datagrid which is probably the most intensive user interaction case for a business app.

With the Abacus DataGrid, every single keystroke event is sent to the browser over a websocket. On each press of the down-cursor key, for examle, the event is sent to APL, which must determine if the grid should scroll, extract and prepare the data to display, render the HTML, send it back over the websocket to the client, which must then replace the innerHMTL of the table element. You can press and hold the cursor key and the datagrid will scroll as smooth and fast as an Excel user would expect. No latency. Awesome.

But we are on one machine. What would happen if we tried to run the datagrid in a web app? Over the internet. From a client in Rome to a server in Los Angeles? At the Carlisle Group 2024 Italy Moot, we tried just that. Amazingly there hardly appeared to be any difference. Scrolling appeared to be just as smooth and fast. I assume it had to be a little slower, we just couldn't really notice it. It was not a scientific test, we just just scrolled around and observed how the performance felt.

Next, we tried 3 connections/users in Rome to the same server in LA. What would happen if all 3 users tried to scroll around? Here we assumed the performance would degrade significantly. Asking a single APL server to handle a flood of keystroke events from multiple clients, where each requires not trivial processing, would be asking too much. We were not wrong, the performance degraded profoundly.

It remains to be seen what architectural options there are for heavily interactive single-user web apps in this model that require a lot of server power for each user. Maybe a different Docker container for each user, each with its own APL instance is viable, for a relatively small number users. Not sure how this would work, or even if it could, for a multi-user app if the users have their own APL instance.

For multiuser apps that do not require that much server power per user, the Abacus model of the client passing every event to APL via a WebSocket may turn out to be quite viable.

We'll see.