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Re: GJS WebKit2 Extension

Actually the `notify::title` with a prefixed "secret-channel" and serialized JSON looks like the best of them all, for the time being, as it makes it straight forward for both client and server to communicate.

```js
// listen to each response
new MutationObserver(m => {
  if (/^secret:response=/.test(document.title)) {
    const data = "">
    document.title = '';
    console.log(data);
  }
}).observe(
  document.querySelector('title'),
  {childList: true}
);

// send info using client or simulate server sending in responses
document.title = 'secret:response=' + JSON.stringify({some: 'value'});
```

with a proper class/wrap to handle events and send data transparently it might be a great way to exchange info



On Wed, Nov 1, 2017 at 5:53 AM, Sam Jansen <sam jansen starleaf com> wrote:


On 1 November 2017 at 05:43, <philip chimento gmail com> wrote:
On Thu, Oct 12, 2017 at 5:23 AM Andrea Giammarchi <andrea giammarchi gmail com> wrote:
FWIW I've used the location with a private channel as protocol to intercept calls to/from the page and GJS.



From the page, which is aware of the "secret" channel, I call GJS actions via location.href = "">Component(JSON.stringify(value))})`;

The protocol secret1234 is intercepted and the `controller.method(JSON.parse(decodeURIComponent(restOfURI)))` invoked.

To signal the page everything is fine I use this.webView.runJavaScript https://github.com/WebReflection/jsgtk-twitter/blob/master/app#L377

The page has a listener for the `secret1234` event on the main window, and such listener is instrumented to react accordingly with the CustomEvent .detail payload/info.

This might look a bit convoluted, and it has JSON serialization as limitation for the kind of data you want to pass (i.e. I use base64 encoded images as source from remotely fetched files enabling somehow CORS for whatever I want) but it worked well, circumventing the missing communication channel available in Qt.

Maybe today there are better ways for doing a similar thing and if that's the case, please share.

Here is another, fairly new, way to do it. Start out by registering a "script message handler":

To send a message to the page, use the same thing that Andrea uses:

To send a message from the page to the GJS program, use the postMessage() method mentioned in the documentation, and connect to this signal in your GJS program to receive the message:


Excellent - I had not noticed this. My first attempt at communicating between WebKit2 and GJS was via setting "document.title" and having GJS connect to the "notify::title" signal! Not a great approach, this looks much better.
 
Although I just realized that unfortunately the values won't be able to be marshalled into GJS since you need to use the _javascript_Core API to get at them. This is a really nice method in C, but in JS you can only use it to send a message without any content. That is annoying. I should probably open up an issue about this.


I just hit upon this problem myself. In researching it, I found it is solved (at least well enough for my use-case) with this open source library:


It's awkward having another dependency for me, especially one that isn't in a normal Ubuntu/Fedora/etc. package, but otherwise this approach worked fine for me.
 
On Wed, Oct 11, 2017 at 12:57 PM, Adriano Patrizio <adriano patrizio hotmail com> wrote:
Thank you for response, this is my problem: have necessity to implement methods into my web application webkit2 based and comunicate with GJS script (example: filesystem functions to read and write files or window managment).

Regards,
Philip C 

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