dot.R

#' Convert `Graphviz` dot content to a SVG
#'
#' Convert a `graphviz` dot digraph as string to `SVG` as string
#'
#' @param dot a `graphviz` dot string
#'
#' @return the SVG as a string
#' @export
#'
#' @examples
#' dot2svg("digraph { A->B }")
dot2svg <- function(dot) {

  if(!requireNamespace("V8", quietly = TRUE)) stop("V8 package is required", call. = FALSE)
  if (!(utils::packageVersion("V8") >= "1.0")) {
    stop('your "V8" package is too old. The DOT package requires V8
        package version 1.0 or newer', call. = FALSE)
  }
  # remove the "\n" from DOT source

  scriptDOT <- gsub("[\r\n]", " ", dot)
  scriptDOT <- gsub("'", "\"", scriptDOT)
  dot <- paste("'", scriptDOT, "'", sep="")

  JS <- system.file("lib/viz.js", package = "dtrackr")
  # this is an old vis.js
  # newer versions are here https://github.com/aduh95/viz.js but use npm and assume node.

  ENV <- V8::v8();
  ENV$source(JS)
  call <- paste("image = Viz(", dot, ")", sep = "")
  content <- ENV$eval(call)
  return(content)

  # viewer <- getOption("viewer")
  # if (!is.null(viewer) & display) {
  #   viewer(dotFile)
  # }

}

#' Standard paper sizes
#'
#' A list of standard paper sizes for outputting flowcharts or other dot
#' graphs. These include width and height dimensions in inches and can be
#' used as one way to specify the output size of a dot graph, including
#' flowcharts (see the `size` parameter of [dtrackr::flowchart()]).
#'
#' The sizes available are `A4`, `A5`, `full` (fits a portrait A4 with margins), `half` (half an
#' A4 with margins), `third`, `two_third`, `quarter`, `sixth` (all with reference to
#' an A4 page with margins). There are 2 landscape sizes `A4_landscape` and `full_landscape` which
#' fit an A4 page with or without margins. There are also 2 slide dimensions,
#' to fit with standard presentation software dimensions.
#'
#' This is just a convenience. Similar effects can be achieved by providing `width` and `height`
#' parameters to [dtrackr::flowchart()] directly.
#'
#' @export
std_size = list(
  A4 = list(width=8.25,height=11.75,rot=0),
  A5 = list(width=5+7/8,height=8.25,rot=0),
  full =  list(width=5.9,height=8,rot=0),
  half =  list(width=5.9,height=4,rot=0),
  third =  list(width=5.9,height=3,rot=0),
  two_third = list(width=5.9,height=6,rot=0),
  quarter = list(width=5.9,height=2,rot=0),
  sixth = list(width=3,height=3,rot=0),
  A4_landscape = list(width=8.25, height=11.75,rot=270),
  full_landscape =  list(width=5.9,height=8,rot=270),
  slide_16_9 = list(width=9.32,height=4.5,rot=0),
  slide_4_3 = list(width=9.32,height=6,rot=0)
)

#' Save DOT content to a file
#'
#' Convert a digraph in dot format to SVG and save it to a range of output file types
#'
#' @param dot a `graphviz` dot string
#' @param filename the full path of the file name (minus extension for multiple
#'   formats)
#' @param size a named list with 3 elements, length and width in inches and
#'   rotation. A predefined set of standard sizes are available in the
#'   [dtrackr::std_size] object.
#' @param maxWidth a width (on the paper) in inches if `size` is not defined
#' @param maxHeight a height (on the paper) in inches if `size` is not defined
#' @param formats some of `pdf`,`dot`,`svg`,`png`,`ps`
#' @param landscape rotate the output by 270 degrees into a landscape format.
#'   `maxWidth` and `maxHeight` still apply and refer to the paper width to fit
#'   the flowchart into after rotation. (you might need to flip width and height)
#' @param ... ignored
#'
#' @return a list with items `paths` with the absolute paths of the saved files
#'   as a named list, and `svg` as the SVG string of the rendered dot file.
#' @export
#'
#' @examples
#' save_dot("digraph {A->B}",tempfile())
save_dot = function(dot, filename, size = std_size$half, maxWidth = size$width, maxHeight = size$height, formats=c("dot","png","pdf","svg"), landscape = size$rot!=0, ...) {

  tmp = filename %>% fs::path_ext()
  if(tmp %in% c("dot","png","pdf","svg","ps")) formats=tmp
  filename = filename %>% fs::path_ext_remove()
  fname = function(extn, suffix = NULL) normalizePath(paste0(c(filename,suffix),collapse="_") %>% fs::path_ext_set(extn),mustWork = FALSE)

  if ("dot" %in% formats) {
    # message("saving dot to: ",fname("dot"))
    suppressMessages(unlink(fname("dot")))
    dot %>% writeChar(fname("dot"))
  }

  svg = dot %>% dot2svg()
  svg = svg %>% .scale_svg(maxWidth, maxHeight, landscape)

  if ("pdf" %in% formats) {
    svg %>% charToRaw() %>% rsvg::rsvg_pdf(
      file = fname("pdf")
    )
    try(
      grDevices::embedFonts(fname("pdf")),
      silent=TRUE
    );
  }

  if ("png" %in% formats) {

    # this is written to pdf first then converted to png and I think this
    # was also done because of a difference in PDF and PNG scaling in rsvg
    # versions prior to 2.4.0, In 2.4.0 this was changed for PNG but to make it
    # easy we are sticking with this and scaling the SVG printing to PDF
    # and rescaling the PDF to PNG at 300 dpi.

    if (!fs::file_exists(fname("pdf"))) {
      tmp = tempfile()
      svg %>% charToRaw() %>% rsvg::rsvg_pdf(file = tmp)
    } else {
      tmp = fname("pdf")
    }
    pdftools::pdf_render_page(tmp,page = 1,dpi=300) %>%
      png::writePNG(fname("png"))
  }

  if ("svg" %in% formats) {

    # With this approach we don't need to "render" the SVG
    # but that then requires the correct fonts are available on the
    # rendering system. RSVG will convert fonts to glphs and remove this dependency
    # but at the cost of preventing further editing.
    svg %>% writeChar(fname("svg"))
    # svg %>% charToRaw() %>% rsvg::rsvg_svg(
    #   file = fname("svg")
    # )

  }

  if ("ps" %in% formats) {
    svg %>% charToRaw() %>% rsvg::rsvg_ps(
        file = fname("ps")
    )
  }

  paths =  as.list(sapply(formats,fname))
  return(
    list(
      paths = paths,
      svg = svg
  ))


}


.scale_svg = function(svg, maxWidth = NULL, maxHeight=NULL, landscape=FALSE, dpi = 72) {

  defaultWidth = (svg %>% stringr::str_match("width=\"([0-9]*)pt\""))[1,2] %>% as.numeric()
  defaultHeight = (svg %>% stringr::str_match("height=\"([0-9]*)pt\""))[1,2] %>% as.numeric()

  if (is.null(maxWidth)) maxWidth = (if (landscape) defaultHeight else defaultWidth)/72
  if (is.null(maxHeight)) maxHeight = (if (landscape) defaultWidth else defaultHeight)/72

  # Calculate a minimum scale based on xscale and yscale then apply that to
  # both X and Y. Then rotating things using svg. the origin of rotation requries
  # a translation (which is on the original scale of the image)
  # The small transform offsets are needed to align the content to the viewport
  dpi = 72
  if (landscape) {
    scale = min(1, maxHeight*72/defaultWidth, maxWidth*72/defaultHeight) * dpi/72
    targetWidth = defaultWidth*scale
    targetHeight = defaultHeight*scale
    transform=sprintf("scale(%1.3f %1.3f) rotate(270) translate(-%1.3f %1.3f)", scale,scale, defaultWidth-4, defaultHeight-4)
    viewBox=sprintf("0 0 %1.3f %1.3f", targetHeight, targetWidth)
    width=sprintf("%1.3fpt", targetHeight)
    height=sprintf("%1.3fpt", targetWidth)
  } else {
    scale = min(1, maxWidth*72/defaultWidth, maxHeight*72/defaultHeight) * dpi/72
    targetWidth = defaultWidth*scale
    targetHeight = defaultHeight*scale
    transform=sprintf("scale(%1.3f %1.3f) rotate(0) translate(4 %1.3f)", scale, scale, defaultHeight-4)
    viewBox=sprintf("0 0 %1.3f %1.3f", targetWidth, targetHeight)
    width=sprintf("%1.3fpt", targetWidth)
    height=sprintf("%1.3fpt", targetHeight)
  }

  # perform all scaling within the SVG
  svg = svg %>%
    stringr::str_replace_all("width=\"([0-9]*)pt\"", sprintf("width=\"%s\"", width)) %>%
    stringr::str_replace_all("height=\"([0-9]*)pt\"", sprintf("height=\"%s\"", height)) %>%
    stringr::str_replace_all("viewBox=\"[^\"]+\"", sprintf("viewBox=\"%s\"", viewBox)) %>%
    stringr::str_replace_all("transform=\"[^\"]+\"", sprintf("transform=\"%s\"", transform))

  return(svg)
}