/*
 * Method which inserts a full background-image property for a theme image.
 * It checks if the file exists and if it doesn't, it'll throw an error.
 * By default it will not include the background-image property if it is not found,
 * but this can be changed by changing the default value of $include-missing-images to
 * be true.
 */
@function theme-background-image($path, $extension: $image-extension, $nocheck: true) {
  $path: file_join($relative-image-path-for-uis, $path + '.' + $extension);
  $background-image: none;

  @if $path {
    @if $nocheck {
      $background-image: $path;
    } @else if theme_image_exists($image-search-path, $path) {
      $background-image: $path;
    } @else {
      @warn "@theme-background-image: Theme image not found: #{$path}";
      @if $include-missing-images {
        $background-image: $path;
      }
    }

    @if $background-image != none {
      $background-image: url(file_join($theme-resource-path, $path));
    }
  } @else {
    @warn "@theme-background-image: No arguments passed";
  }

  @return $background-image;
}
