Re: GJS WebKit2 Extension

[Sam Jansen <sam jansen starleaf com>]

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.

https://github.com/WebReflection/jsgtk-twitter/blob/master/app#L162-L175

The channel is a random string: https://github.com/WebReflection/jsgtk-twitter/blob/master/app#L59

From the page, which is aware of the "secret" channel, I call GJS actions via location.href = "">encodeURIComponent(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":

http://devdocs.baznga.org/webkit240~4.0_api/webkit2.usercontentmanager#method-register_script_message_handler

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

http://devdocs.baznga.org/webkit240~4.0_api/webkit2.webview#method-run_javascript

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:

http://devdocs.baznga.org/webkit240~4.0_api/webkit2.usercontentmanager#signal-script-message-received

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:

https://github.com/saifulbkhan/wkjscore-result

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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