Logging Console Messages

You can get log output for JavaScript errors, network errors, and more to help diagnose issues when writing code for your View.

Seeconsole.log() in JavaScript: https://developer.mozilla.org/en-US/docs/Web/API/console/log_static

Attaching the ViewListener Interface

You should first subclass ViewListener and implement the ViewListener::OnAddConsoleMessage() virtual method.

Then, bind an instance of your subclass to a View via View::set_view_listener().

📘
See the API reference for ViewListener here.

Handling ViewListener::OnAddConsoleMessage()

Here's an example that logs console messages to std::cout:

#include <Ultralight/Ultralight.h>
#include <iostream>
  
using namespace ultralight;

//
// Inherited from ViewListener::OnAddConsoleMessage
//
// Make sure that you bind 'MyApp' to 'View::set_view_listener'
// to receive this event.
//
void MyApp::OnAddConsoleMessage(View* caller, const ConsoleMessage& msg) {
    std::cout << "[OnAddConsoleMessage]\n\t"
              << "\n\tsource:\t" << (uint32_t)msg.source()
              << "\n\ttype:\t" << (uint32_t)msg.type()
              << "\n\tlevel:\t" << (uint32_t)msg.level()
              << "\n\tmessage:\t" << msg.message().utf8().data()
              << "\n\tline_number:\t" << msg.line_number()
              << "\n\tcolumn_number:\t" << msg.column_number()
              << "\n\tsource_id:\t" << msg.source_id().utf8().data()
              << "\n\tnum_arguments:\t" << msg.num_arguments() << std::endl;

    // console.log() in JavaScript can be passed multiple arguments-- you can
    // get the raw JavaScript values passed to the function via the following:
    uint32_t num_args = msg.num_arguments();
    if (num_args > 0) {
        for (uint32_t i = 0; i < num_args; i++) {
            JSValueRef arg = msg.argument_at(i);
            // Optionally print the argument here, see the JavaScriptCore API
            // for converting these values to a string.
        }
    }
}