Add WebView.MessageReceived

[camnewnham]

Hello! Initial draft for discussion.

The goal of this PR is to create a uniform approach to sending events from JS to Eto. Combined with the existing ExecuteScript it should allow for bi-directional communication (without polling).

Since each browser implementation significantly differs this approach is intended to keeps it simple by adding a single object /method to the global JavaScript context.

Example usage:

function isRunningInEto() {
  return window.eto !== undefined;
}

function onButtonClick() {
   window.eto.postMessage("The button was clicked!");
}

Supported Implementations:

• [x] WebView (legacy) (Wpf and WinForms)
• [x] WebView2 (Wpf and WinForms)
• [x] WebKit.WKWebView (Mac64 and MacOS)

Not implemented:

• [ ] WebKit.WebView (legacy)
• [ ] GTK

[cwensley]

Hey @camnewnham, this is looking great! This will help a lot of custom script scenarios.

Do you need help with the GTK implementation or is that something you'll be able to do?

[camnewnham]

Do you need help with the GTK implementation or is that something you'll be able to do?

That would be appreciated - I don't currently have a Linux machine (or is this testable on other platforms?)

Is a legacy WebKit.WebView implementation required?