R/assemble_header.R

In accessrmd: Improving the Accessibility of 'rmarkdown' Documents

#' Assemble HTML header output from text provided.
#'
#' Returns header structure for use with 'access_head()' and 'access_rmd()'.
#'
#' @param title Text string to use as document title and h1 heading.
#' @param subtitle Text string to use as subtitle heading.
#' @param auth Text string or inline code to include as author heading.
#' @param doc_date Text string or inline code to include as date heading.
#' @param enc Text string to use as document encoding.
#'
#' @return An assembled html output page containing the required toc code.
#'
assemble_header <- function(title, subtitle = NULL, auth, doc_date, enc) {
  if (length(title) == 0) {
    stop("No document title found. Please adjust the Rmarkdown.")
  }
  # produce the accessible title
  html_title <- tags$title(title)
  # h1 needs to be the same as title
  h1_content <- tags$h1(title, class = "title toc-ignore")

  if (is.null(subtitle) | length(subtitle) == 0) {
    h2_auth <- return_heading(txt = auth, lvl = 2, class = "author")
    h2_date <- return_heading(txt = doc_date, lvl = 2, class = "date")
    metas <- list(h2_auth, h2_date)
  } else {
    h2_sub <- return_heading(txt = subtitle, lvl = 2, class = "subtitle")
    h3_auth <- return_heading(txt = auth, lvl = 3, class = "author")
    h3_date <- return_heading(txt = doc_date, lvl = 3, class = "date")
    metas <- list(h2_sub, h3_auth, h3_date)
  }

  # assemble header ---------------------------------------------------------
  html_head <- tags$header(
    tags$meta(charset = enc),
    html_title,
    h1_content,
    metas
  )
  return(html_head)
}