1. I have implemented a variant on the evaluate JavaScript setup documented here (my purpose being to return a string based on the result of a function): https://webkitgtk.org/reference/webkitgtk/unstable/method.WebView.evaluate_javascript.html

2. See my variant below, noting that the documentation version only prints, where as my version sets user_data to be a pointer to the result.

3. web_view_javascript_finish() runs async, so I need to wait for it to finish before I take the value and carry on with the process.

4. I've read about a few methods for waiting (semaphores, mutexes, etc.) but I tried a basic method first, running while (!result) {} so that when the result goes from NULL to a string value, things will proceed.

5. However, when I run without this line, everything works as expected, and perhaps unsurprisingly, the printf("result element: %s\n",result); prints null,, I think because it got there before the JavaScript completed.

6. However, with while (!result) {}, web_view_javascript_finished() appears not to run at all (nothing is printed).

I want to resolve this issue before I move forward with any other solution. I welcome your thoughts!

static void
web_view_javascript_finished (GObject      *object,
                              GAsyncResult *result,
                              gpointer      user_data)
{
    
    JSCValue               *value;
    GError                 *error = NULL;

    value = webkit_web_view_evaluate_javascript_finish (WEBKIT_WEB_VIEW (object), result, &error);

    if (!value) {
        g_warning ("1 Error running javascript: %s\n", error->message);
        g_error_free (error);
        return;
    }

    if (jsc_value_is_string (value)) {
        gchar        *str_value = jsc_value_to_string (value);
        JSCException *exception = jsc_context_get_exception (jsc_value_get_context (value));
        if (exception)
            g_warning ("2 Error running javascript: %s\n", jsc_exception_get_message (exception));
        else
            g_print ("3 Script result: %s\n", str_value);
        g_free (str_value);
    } else {
        g_warning ("4 Error running javascript: unexpected return value\n");
    }
    gchar        *str_value = jsc_value_to_string (value);
    g_print ("Script result: %s\n", str_value);
    user_data = str_value;
    g_print ("user_data result: %s\n", user_data
    g_object_unref (value);
}

static char *web_view_get_element_info (WebKitWebView *web_view,
                       const gchar   *uuid)
{
    gchar *script = g_strdup_printf ("el = window.document.getElementById('%s'); el_rect = el.getBoundingClientRect(); JSON.stringify(el_rect); ");
    char *result = NULL;
    webkit_web_view_evaluate_javascript (web_view, script, -1, NULL, NULL, NULL, web_view_javascript_finished, &result);
    while (!result) {}
    printf("result element: %s\n",result);
    return web_result;
    g_free (script);
}