Downstream Event System

[johnpatek]

The IPC bridge currently allows for basic CRUD operations over HTTP, but this is not especially useful for anyone who wants to push things from backend to frontend. The obvious solution would be WebSockets, but wxWidgets does not support WebSockets on any of its backends. What it does support is the ability to inject JavaScript and retrieve the result. There are a few possible solutions:

1. Highly abstract event system that creates an abstract stream above WebSockets/script injection.
2. Add WebSockets to wxWidgets.
3. Use an embedded WebSocket server to run alongside the desktop runtime.

Each solution has its pros and cons, and I am nowhere near a decision on how to approach this.

[johnpatek]

Possible solution: model the event push based on RunScriptAsync, and use a websocket to emulate the same behavior on a webserver. Still some details to work out like how to keep track of event senders/receivers, but it is a potential solution to this problem.

[johnpatek]

Research findings:

• In the effort to maintain consistency with https schemes from the frontend, it appears that only CEF and Edge are viable platforms.
• Only Edge has the ability to handle WebSockets through its in-process networking stack, which means the virtual host mapping on CEF will not work for WebSocket traffic.
• Both platforms support a basic HTTP request/response mechanism with optional deferred writing to response streams, which is hidden by the wxWidgets implementation(my fault on the CEF side I suppose).

Proposed solution:
By using the response stream mechanisms offered by CEF and Edge, we can create a working downlink via SSE. In a separate project, we can create a wxWebEngine class, which can map HTTP handlers by virtual host, and provide less opinionated request/response handling. For the sake of convenience, it can create webviews and bind their handles to the Edge resource filters or CEF scheme handlers under the hood. WebFrame will need only one virtual host, so the main concern here will be how the WebFrame API interacts with the wxWebEngine handler interface.