function twentyseventeen_customize_register( $wp_customize ) {
  $wp_customize->get_setting( 'blogname' )->transport         = 'postMessage';
  $wp_customize->get_setting( 'blogdescription' )->transport  = 'postMessage';
  $wp_customize->get_setting( 'header_textcolor' )->transport = 'postMessage';

  $wp_customize->selective_refresh->add_partial(
    'blogname',
    array(
      'selector'        => '.site-title a',
      'render_callback' => 'twentyseventeen_customize_partial_blogname',
    )
  );
  $wp_customize->selective_refresh->add_partial(
    'blogdescription',
    array(
      'selector'        => '.site-description',
      'render_callback' => 'twentyseventeen_customize_partial_blogdescription',
    )
  );

  
/**
 * Custom colors.
 */
  $wp_customize->add_setting(
    'colorscheme',
    array(
      'default'           => 'light',
      'transport'         => 'postMessage',
      'sanitize_callback' => 'twentyseventeen_sanitize_colorscheme',
    )
  );

  $wp_customize->add_setting(
    'colorscheme_hue',
    array(
      'default'           => 250,
      'transport'         => 'postMessage',
      'sanitize_callback' => 'absint', // The hue is stored as a positive integer.
    )
  );

  $wp_customize->add_control(
    'colorscheme',
    array(
      'type'     => 'radio',
      'label'    => __( 'Color Scheme', 'twentyseventeen' ),
      'choices'  => array(
        'light'  => __( 'Light', 'twentyseventeen' ),
        'dark'   => __( 'Dark', 'twentyseventeen' ),
        'custom' => __( 'Custom', 'twentyseventeen' ),
      ),
      'section'  => 'colors',
      'priority' => 5,
    )
  );

  $wp_customize->add_control(
    new WP_Customize_Color_Control(
      $wp_customize,
      'colorscheme_hue',
      array(
        'mode'     => 'hue',
        'section'  => 'colors',
        'priority' => 6,
      )
    )
  );

  
/**
 * Theme options.
 */
  $wp_customize->add_section(
    'theme_options',
    array(
      'title'    => __( 'Theme Options', 'twentyseventeen' ),
      'priority' => 130, // Before Additional CSS.
    )
  );

  $wp_customize->add_setting(
    'page_layout',
    array(
      'default'           => 'two-column',
      'sanitize_callback' => 'twentyseventeen_sanitize_page_layout',
      'transport'         => 'postMessage',
    )
  );

  $wp_customize->add_control(
    'page_layout',
    array(
      'label'           => __( 'Page Layout', 'twentyseventeen' ),
      'section'         => 'theme_options',
      'type'            => 'radio',
      'description'     => __( 'When the two-column layout is assigned, the page title is in one column and content is in the other.', 'twentyseventeen' ),
      'choices'         => array(
        'one-column' => __( 'One Column', 'twentyseventeen' ),
        'two-column' => __( 'Two Column', 'twentyseventeen' ),