svg_logo.module

<?php
/**
  * Implement hook_form_alter(&$form,&$form_state,$form_id)
  */
function svg_logo_form_alter(&$form,&$form_state,$form_id) {
  switch ($form_id) {
    case 'system_theme_settings':
      // duplicate logo form for svg
      $add_svg_logo = $form['logo']['default_logo'];
      $svg_path = $form['logo']['settings']['logo_path'];
      $svg_upload = $form['logo']['settings']['logo_upload'];
      // adaped some description
      $add_svg_logo['#title'] = t('Use a svg logo');
      $svg_path['#title'] = t('Path to custom svg logo');
      $svg_upload['#title'] = t('Upload logo svg image');
      $add_svg_logo['#description'] = t('Check here if you want the theme to use a svg logo if the browser supports it.');
      $svg_path['#description'] = t('The path to the file you would like to use as your svg logo file instead of the default logo.');
      $svg_upload['#description'] = t('If you don\'t have direct file access to the server, use this field to upload your svg logo.');
      // get theme name to get settings
      $theme_settings_name = $form['var']['#value'];
      $theme_settings_array = explode('_', $theme_settings_name);
      $theme_settings_array_count = count($theme_settings_array);
      $theme_name = ($theme_settings_array_count > 2)?$theme_settings_array[1]:null;
      // if theme name has underscrores
      if($theme_settings_array_count > 3) {
        $theme_name = '';
        foreach ($theme_settings_array as $key => $value) {
          if($key != 0 && $key != ($theme_settings_array_count-1)) {
            $theme_name .= $value;
            if($key != ($theme_settings_array_count-2)) {
              $theme_name .= '_';
            }
          }        
        }
      }
      // get default value if there is any
      $add_svg_logo['#default_value'] = theme_get_setting('svg_logo', $theme_name);
      $svg_path['#default_value'] = theme_get_setting('svg_logo_path', $theme_name);
      // If path is a public:// URI, display the path relative to the files
      // directory; stream wrappers are not end-user friendly.
      $original_path = $svg_path['#default_value'];
      $friendly_path = NULL;
      if (file_uri_scheme($original_path) == 'public') {
        $friendly_path = file_uri_target($original_path);
        $svg_path['#default_value'] = $friendly_path;
      }
      // add container
      $form['logo']['settings']['svg'] = array(
        '#type' => 'container', 
        '#states' => array(
          // Hide the logo settings when using the default logo.
          'invisible' => array(
            'input[name="svg_logo"]' => array('checked' => False),
          ),
        ),
        '#weight' => 5,
      );
      // weight for the right order
      $add_svg_logo['#weight'] = 4;
      // add back to form
      $form['logo']['settings']['svg_logo'] = $add_svg_logo;
      $svg_path = $form['logo']['settings']['svg']['svg_logo_path'] = $svg_path;
      $svg_upload = $form['logo']['settings']['svg']['svg_logo_upload'] = $svg_upload;
      // add validator and submit function for svg path or upload
      $form['#validate'][] = 'svg_logo_theme_settings_validate';
      $form['#submit'][] = 'svg_logo_theme_settings_submit';
      break;
  }
}

/**
 * Implements svg_logo_theme_settings_validate($form,&$form_state)
 */
function svg_logo_theme_settings_validate($form,&$form_state) {
  // Handle file uploads.
  $validators = array('file_validate_extensions' => array('svg'));

  // Check for a new uploaded logo.
  $file = file_save_upload('svg_logo_upload', $validators);
  if (isset($file)) {
    // File upload was attempted.
    if ($file) {
      // Put the temporary file in form_values so we can save it on submit.
      $form_state['values']['svg_logo_upload'] = $file;
    }
    else {
      // File upload failed.
      form_set_error('svg_logo_upload', t('The svg logo could not be uploaded.'));
    }
  }

  // If the user provided a path for a logo or favicon file, make sure a file
  // exists at that path.
  if ($form_state['values']['svg_logo_path']) {
    $path = _system_theme_settings_validate_path($form_state['values']['svg_logo_path']);
    if (!$path) {
      form_set_error('svg_logo_path', t('The custom svg logo path is invalid.'));
    }
  }
}

/**
 * Implements svg_logo_theme_settings_submit($form,&$form_state)
 */
function svg_logo_theme_settings_submit($form,&$form_state) {
  $values = $form_state['values'];
  // If the user uploaded a new logo or favicon, save it to a permanent location
  // and use it in place of the default theme-provided file.
  if ($file = $values['svg_logo_upload']) {
    unset($values['svg_logo_upload']);
    $filename = file_unmanaged_copy($file->uri);
    $values['svg_logo'] = 1;
    $values['svg_logo_path'] = $filename;
  }
  // If the user entered a path relative to the system files directory for
  // a logo, store a public:// URI so the theme system can handle it.
  if (!empty($values['svg_logo_path'])) {
    $values['svg_logo_path'] = _system_theme_settings_validate_path($values['svg_logo_path']);
  }
  // load current theme settings to add svg settings
  $key = $values['var'];
  $theme_settings = variable_get($key);
  // clean settings up - just to be shure
  unset(
    $theme_settings['logo_upload'],
    $theme_settings['svg_logo_upload'],
    $theme_settings['var'],
    $theme_settings['submit'],
    $theme_settings['reset'],
    $theme_settings['form_id'],
    $theme_settings['op'],
    $theme_settings['form_build_id'],
    $theme_settings['form_token']
  );
  // add svg settings 
  $theme_settings['svg_logo'] = $values['svg_logo'];
  $theme_settings['svg_logo_path'] = $values['svg_logo_path'];
  // save theme settings an clear cache
  variable_set($key, $theme_settings);
  cache_clear_all();
}

/**
 * Override or insert variables into the page template.
 */
function svg_logo_process_page(&$variables) {
  $svg_path = theme_get_setting('svg_logo_path');
  $variables['svg_logo'] = file_create_url($svg_path);
}