make a pdf in R with hpdf.js - emscripten port of libharu

code.R

# run these hpdf.js examples
#   http://manuels.github.io/hpdf.js/
# in R with V8

library(V8)
library(pipeR)
library(htmltools)

ct = new_context("window")
ct$source("https://raw.githubusercontent.com/manuels/hpdf.js/master/hpdf.min.js")

# hpdf needs a base64 encode like windows.btoa
#   we'll use this implementation
# https://code.google.com/p/stringencoders/source/browse/trunk/javascript/base64.js?r=230
ct$source(
  "https://stringencoders.googlecode.com/svn-history/r230/trunk/javascript/base64.js"
)
# use the base64 encode and make it windows.btoa
ct$eval(
  "window.btoa = base64.encode"
)


ct$eval(
'
  var pdf = new HPDF();
  
  var helvetica = pdf.font("Helvetica");
  
  var title = "This is a test!";
  var page = pdf.addPage();
  page.setFontAndSize(helvetica, 24);
  var tw = page.textWidth(title);
  page.beginText();
  page.moveTextPos( (page.width()-tw)/2, page.height()-50 );
  page.showText(title);
  page.endText();
  pdf.toDataUri();
') %>>%
  # can't figure out how to pass base64 to R browseURL
  # so use iframe instead
  (html_print(
    tags$iframe(src = ., style = "border: 0; position:fixed; top:0; left:0; right:0; bottom:0; width:100%; height:100%")
    # RStudio Viewer doesn't show the pdf
    ,viewer = utils::browseURL
  ) )


ct$eval("
function print_grid(pdf, page) {
  var height = page.height();
  var width = page.width();
  var font = pdf.font('Helvetica');
  
  page.setFontAndSize(font, 5);
  page.setGrayFill(0.5);
  page.setGrayStroke(0.8);
  
  /* Draw horizontal lines */
  var y = 0;
  while (y < height) {
  if (y % 10 == 0)
  page.setLineWidth(0.5);
  else {
  if (page.getLineWidth() != 0.25)
  page.setLineWidth(0.25);
  }
  
  page.moveTo(0, y);
  page.lineTo(width, y);
  page.stroke();
  
  if (y % 10 == 0 && y > 0) {
  page.setGrayStroke(0.5);
  
  page.moveTo(0, y);
  page.lineTo(5, y);
  page.stroke();
  
  page.setGrayStroke(0.8);
  }
  
  y += 5;
  }
  
  
  /* Draw virtical lines */
  var x = 0;
  while (x < width) {
  if (x % 10 == 0)
  page.setLineWidth(0.5);
  else {
  if (page.setLineWidth() != 0.25)
  page.setLineWidth(0.25);
  }
  
  page.moveTo(x, 0);
  page.lineTo(x, height);
  page.stroke()
  
  if (x % 50 == 0 && x > 0) {
  page.setGrayStroke(0.5);
  
  page.moveTo(x, 0);
  page.lineTo(x, 5);
  page.stroke();
  
  page.moveTo(x, height);
  page.lineTo(x, height - 5);
  page.stroke();
  
  page.setGrayStroke(0.8);
  }
  
  x += 5;
  }
  
  /* Draw horizontal text */
  y = 0;
  while (y < height) {
  if (y % 10 == 0 && y > 0) {
  page.beginText();
  page.moveTextPos(5, y - 2);
  page.showText(y.toString());
  page.endText();
  }
  
  y += 5;
  }
  
  
  /* Draw virtical text */
  x = 0;
  while (x < width) {
  if (x % 50 == 0 && x > 0) {
  page.beginText();
  page.moveTextPos(x, 5);
  page.showText(x.toString());
  page.endText();
  
  page.beginText();
  page.moveTextPos(x, height - 10);
  page.showText(x.toString());
  page.endText();
  }
  
  x += 5;
  }
  
  page.setGrayFill(0);
  page.setGrayStroke(0);
  }
  
  var pdf = new HPDF();
  
  /* add a new page object. */
  var page = pdf.addPage();
  
  page.setHeight(220);
  page.setWidth(200);
  
  /* draw grid to the page */
  print_grid(pdf, page);
  
  /* draw pie chart
  *
  *   A: 45% Red
  *   B: 25% Blue
  *   C: 15% green
  *   D: other yellow
  */
  
  /* A */
  page.setRGBFill(1.0, 0, 0);
  page.moveTo(100, 100);
  page.lineTo(100, 180);
  page.arc(100, 100, 80, 0, 360 * 0.45);
  pos = page.currentPos();
  page.lineTo(100, 100);
  page.fill();
  
  /* B */
  page.setRGBFill(0, 0, 1.0);
  page.moveTo(100, 100);
  page.lineTo(pos.x, pos.y);
  page.arc(100, 100, 80, 360 * 0.45, 360 * 0.7);
  pos = page.currentPos();
  page.lineTo(100, 100);
  page.fill();
  
  /* C */
  page.setRGBFill(0, 1.0, 0);
  page.moveTo(100, 100);
  page.lineTo(pos.x, pos.y);
  page.arc(100, 100, 80, 360 * 0.7, 360 * 0.85);
  pos = page.currentPos();
  page.lineTo(100, 100);
  page.fill();
  
  /* D */
  page.setRGBFill(1.0, 1.0, 0);
  page.moveTo(100, 100);
  page.lineTo(pos.x, pos.y);
  page.arc(100, 100, 80, 360 * 0.85, 360);
  pos = page.currentPos();
  page.lineTo(100, 100);
  page.fill();
  
  /* draw center circle */
  page.setGrayStroke(0);
  page.setGrayFill(1);
  page.circle(100, 100, 30);
  page.fill();
  

  pdf.toDataUri()
")  %>>%
  # can't figure out how to pass base64 to R browseURL
  # so use iframe instead
  (html_print(
    tags$iframe(src = ., style = "border: 0; position:fixed; top:0; left:0; right:0; bottom:0; width:100%; height:100%")
    # RStudio Viewer doesn't show the pdf
    ,viewer = utils::browseURL
  ) )