[webkit-gtk] Proper way to load javascript

[Adrian Perez de Castro]

Hello Daniel,

On Sun, 03 Mar 2019 09:04:03 +0100, Daniel Berek <berekdaniel at gmail.com> wrote:

> Hi, I am using gtkmm-3.0 and the new webkit2gtk-4.0 (where the javascript is
> running on a new web process).
>
> I have two problems to solve, which connecting together.
>
> 1. At first, I am not sure whats the proper way to load an external
> javascript file. In this version of webkit, the <script
> src="script.js"></script> tag from html file doesnt work, even the html cant
> be loaded.  So I have to read the 'script.js' manually, and after each
> webkit_web_view_load_html() I have to execute
> webkit_web_view_run_javascript().  Is there a more sophisticated method to
> load external javascript? ex loading once, so all html sites could use it?

This sounds like you would want to have your JavaScript file loaded (and
available) to all the web pages loaded in the Web view. The recommended way of
achieving that is loading the script once with “webkit_user_script_new()” or
“webkit_user_script_new_for_world()” [1], then you would add it to a
WebKitUserContentManager [2] (which you are already using in you example
code), and finally make sure that your web view makes use of your user content
manager (WebKitWebView has a “user-content-manager” property [3]). Then WebKit
will automatically inject your JavaScript code into loaded pages.

> 2. I have a webview widget (described at the end of this message) and I
> periodically called its destructor (default destructor) to get rid off the
> cached data and made a new instance. Unfortunately, deleting the webview
> widget leaks almost 400kB of memory. So I stopped calling its destructor,
> which is perfectly fine for me (no more leaks, I cant even see the
> increasing cache) but after a few javascript execution, my functions in the
> external 'script.js' file doesnt work properly, athough
> the run_javascript_finished_discard_result() doesnt show any error.
>  It seems, the javascript process cant handle that much executions.

It should be fine to call the same JavaScript repeatedly. But I still
recommend you to use WebKitUserContentManager to inject your JavaScript code
because it *will* make your life easier :)

> Somebody knows whats the proper way for deleting a webview widget
> programically?
> Or any help is appreciated.

I think destructing the WebKitWebView should correctly deallocate all the
memory used, those 400 KiB of memory lost are suspicious. Are you sure that
there are no other references to the widget (installed signal callbacks, for
example)? Though it might be a problem inside WebKitGTK itself, dunno…

Which kind of “cached data” do you need to get rid of exactly? You may be able
to keep your Web view around, with the user content manager taking care of
injecting your JavaScript code, and then using WebKitWebsiteDataManager to
clear up caches and other transient data.

Hopefully these tips will help you out a bit :)

Cheers,


-Adrián

---
[1] https://webkitgtk.org/reference/webkit2gtk/stable/webkit2gtk-4.0-WebKitUserContent.html#webkit-user-script-new
[2] https://webkitgtk.org/reference/webkit2gtk/stable/WebKitUserContentManager.html#webkit-user-content-manager-add-script
[3] https://webkitgtk.org/reference/webkit2gtk/stable/WebKitWebView.html#WebKitWebView--user-content-manager
[4] https://webkitgtk.org/reference/webkit2gtk/stable/WebKitWebsiteDataManager.html
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