Block configuration form values are not translated I have the following code in my custom block:

    public function blockForm($form, FormStateInterface $form_state) {
    $form = parent::blockForm($form, $form_state);

    $config = $this-&gt;getConfiguration();

    $form['headline'] = array(
      '#type' =&gt; 'textfield',
      '#title' =&gt; $this-&gt;t('Block headline'),
      '#default_value' =&gt; isset($config['headline']) ? $config['headline'] : NULL,
      '#required' =&gt; TRUE,
    );


      return $form;
    }


and:  

    public function blockSubmit($form, FormStateInterface $form_state) {
      $this-&gt;setConfigurationValue('headline', $form_state-&gt;getValue('headline'));
    }


The configuration is saved correctly, but only for English language.
The block translation doesn't show my variable (headline) in the translatable configuration.
What am I doing wrong?  

Thanks
You have to provide a schema in /config/schema/mymodule.schema.yml of the type block_settings.

Example:

block.settings.example_configurable_text:
  type: block_settings
  label: 'Example configurable text block configuration'
  mapping:
    block_example_string:
      type: text
      label: 'Block contents'


From the example module http://cgit.drupalcode.org/examples/tree/block_example/config/schema/block_example.schema.yml

Configuration values you map as type: label (single line of text) or type: text (multiple lines of text) are translatable.