wp.media.view.ImageDetails - Save settings as HTML5 data-* attributes for image

Question

What I finally want to achieve are extra settings added to the Image Details box, that will be stored in the image <img> tag as data-* attributes

Example: <img src="..." data-my_setting="...">

---

MY CODE

I am creating a plugin, and I need to create more settings for when you edit images. So far I have the following code:

jQuery(function($) {

    var imageDetails = wp.media.view.ImageDetails

    wp.media.view.ImageDetails = wp.media.view.ImageDetails.extend({
        // Initialize - Call function to add settings when rendered
        initialize: function() {
            this.on('post-render', this.add_settings);
        },
        // To add the Settings
        add_settings: function() {
            $('.advanced-section').prepend('\
                <h2>My Settings</h2>\
                <input type="text" class="my_setting">\
            ');

            // Set Options
            this.controller.image.set({"data-settings": 'setting-value-here'})
        }
    });

}) // End of jQuery(function($))

I created a new post and added one image, then clicked on it and pressed Edit (the pencil icon in the toolbar that popped up). I ended up on the image details page, and this is what it looked like:

So far, so good. On this line:

this.controller.image.set({"data-settings": 'setting-value-here'})

I would normally use jQuery to get the value of the input, but for testing purposes I changed it to be a static value of 'setting-value-here'. I pressed 'Update' in the bottom-right corner of the Image Details box.

---

THE PROBLEM

In the Text editor, it shows the HTML code as this:

This does not have a data-settings="setting-value-here", how come?

If I replace the line with this:

 this.controller.image.set({alt: 'setting-value-here'})

It does change the ALT tag to alt="setting-value-here". So what am I doing wrong trying to set the data-* attribute?

---

THE SOLUTION

Thanks to @bonger (who got the full bounty of 50 Reputation), I have the following code:

PHP:

function add_my_settings() {
    ob_start();
    wp_print_media_templates();
    $tpl = ob_get_clean();
    if ( ( $idx = strpos( $tpl, 'tmpl-image-details' ) ) !== false
            && ( $before_idx = strpos( $tpl, '<div class="advanced-section">', $idx ) ) !== false ) {
        ob_start();
        ?>
        <div class="my_setting-section">
            <h2><?php _e( 'My Settings' ); ?></h2>
            <div class="my_setting">
                <label class="setting my_setting">
                    <span><?php _e( 'My Setting' ); ?></span>
                        <input type="text" data-setting="my_setting" value="{{ data.model.my_setting }}" />
                    </label>
                </div>
            </div>
        <?php
        $my_section = ob_get_clean();
        $tpl = substr_replace( $tpl, $my_section, $before_idx, 0 );
    }
    echo $tpl;
};

// Hack the output of wp_print_media_templates()
add_action('wp_enqueue_media', $func =
    function() {
        remove_action('admin_footer', 'wp_print_media_templates');
        add_action('admin_footer',  'add_my_settings');
    }
);

JavaScript: (Needs to be enqueued using wp_enqueue_script())

// When Image is Edited
wp.media.events.on('editor:image-edit', function(data) {
    data.metadata.my_setting = data.editor.dom.getAttrib( data.image, 'data-my_setting' );
});

// When Image is Updated
wp.media.events.on('editor:image-update', function(data) {
    data.editor.dom.setAttrib( data.image, 'data-my_setting', data.metadata.my_setting );
});

Answer 1

A way to do it is to use the (very convenient) editor:image-edit and editor:image-update events triggered by the tinymce wpeditimage plugin to get/set the dom directly (updated to wrap in wp_enqueue_media action):

add_action( 'wp_enqueue_media', function () {
    add_action( 'admin_footer', function () {
        ?>
        <script type="text/javascript">
        jQuery(function ($) {
            if (wp && wp.media && wp.media.events) {
                wp.media.events.on( 'editor:image-edit', function (data) {
                    data.metadata.my_setting = data.editor.dom.getAttrib( data.image, 'data-my_setting' );
                } );
                wp.media.events.on( 'editor:image-update', function (data) {
                    data.editor.dom.setAttrib( data.image, 'data-my_setting', data.metadata.my_setting );
                } );
            }
        });
        </script>
        <?php
    }, 11 );
} );

To add and populate the settings field, it's perhaps groovier to hack the output of wp_print_media_templates() rather than override ImageDetails.initialize() (updated to wrap in wp_enqueue_media action):

add_action( 'wp_enqueue_media', function () {
    remove_action( 'admin_footer', 'wp_print_media_templates' );
    add_action( 'admin_footer', $func = function () {
        ob_start();
        wp_print_media_templates();
        $tpl = ob_get_clean();
        // To future-proof a bit, search first for the template and then for the section.
        if ( ( $idx = strpos( $tpl, 'tmpl-image-details' ) ) !== false
                && ( $before_idx = strpos( $tpl, '<div class="advanced-section">', $idx ) ) !== false ) {
            ob_start();
            ?>
    <div class="my_setting-section">
        <h2><?php _e( 'My Settings' ); ?></h2>
        <div class="my_setting">
            <label class="setting my_setting">
                <span><?php _e( 'My Setting' ); ?></span>
                <input type="text" data-setting="my_setting" value="{{ data.model.my_setting }}" />
            </label>
        </div>
    </div>
            <?php
            $my_section = ob_get_clean();
            $tpl = substr_replace( $tpl, $my_section, $before_idx, 0 );
        }
        echo $tpl;
    } );
} );