[webkit-gtk] Rendering HTML from JavaScript

Anatoly Zaretsky anatoly.zaretsky at gmail.com
Fri Oct 31 16:24:21 PDT 2014

On Thu, Oct 30, 2014 at 9:05 AM, Carlos Garcia Campos wrote:
> No, WebView is the UI process API.
> ...
> If I understood correctly what you want, I think it would be something
> like:
> In the web extension you connect to the window-object-cleared signal,
> and with the exactly same code you currently has extends the window
> object to add renderHTML. In the callback you would need to send a
> message to the UI process, using DBus or any other IPC mechanism you
> want.
> In the UI process, when the message is received you create a WebView,
> connects to load-changed, and loads the HTML using
> webkit_web_view_load_html. In the load-changed signal when the load
> event is finished, you can call webkit_web_view_get_snpashot to
> asynchronously get a cairo image surface with the web view contents
> rendered. Now you need to send another message to the web extension with
> the results.

Yes, this is exactly what I needed, thank you for such a detailed explanation.

> I know it's a bit more complex, because JavaScript is in the WebProcess.
> We are about to land a patch that would simplify this, you wouldn't need
> to extend the window object nor send an IPC message to the UI process.
> Your JavaScript code could do something like
> window.webkit.messageHandlers.renderer.postMessage() and the message
> would be received in the UI process as a signal with a
> WebKitJavaScriptResult object to deserialize.
> See https://bugs.webkit.org/show_bug.cgi?id=133730

Wow, patches landed four hours ago, definitely I chose the right time to ask!

MessageHandlers look very interesting — Is there a similar mechanism
to post messages in the
opposite direction from the UI process to listeners registered by the JavaScript
code? Or do I still need to use some IPC channel for that?

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