Right now I have a nice R Shiny app that is able to create a pdf from parts of it using a piece of javascript. However right now it just automatically downloads.

js <- "
$(document).on('shiny:sessioninitialized', function(event) {
  $('#printPdf_CA').click(function () {
    domtoimage.toPng(document.getElementById('mainOrder_CA'))
      .then(function (blob) {
        var pdf = new jsPDF('l', 'pt', [$('#mainOrder_CA').width(), $('#mainOrder_CA').height()]);
        pdf.addImage(blob, 'PNG', 0, 0, $('#mainOrder_CA').width(), $('#mainOrder_CA').height());
        pdf.save($('#name').val() + '.pdf');
      });
  });
});
"

I want to be able to store it locally (either as a file in a relative directory OR as a variable in the Shiny app) and then give the user the choice to either print it to pdf(like above) OR send it over email to a chosen adress (using the emayili package from R). I allready tried Shiny.setInputValue(), but that did not work at all (even just sending a number from the javascript didn't seem to work, but maybe I am doing something wrong here.

I would really appreciate your help!

EDIT I made Shiny.setinputValue() work, but don't know how to write it to a temporary .pdf file from the field. I also wonder if this still is officially recognized as a pdf or if there was some information loss when moved to R

EDIT 2: Basically I manage to send the PDF to R as a shiny input with the following adjusted code:

$(document).on('shiny:sessioninitialized', function(event) {
var pdf
  $('#storePDF').click(function () {
    domtoimage.toPng(document.getElementById('Capture'))
      .then(function (blob) {
        pdf = new jsPDF('l', 'pt', [$('#Capture').width(), $('#Capture').height()]);
        pdf.addImage(blob, 'PNG', 0, 0, $('#Capture').width(), $('#Capture').height());
        Shiny.setInputValue('pdf', pdf)
      });
  });
});

Now I would just need to be able to create a PDF in R from this. However in R the resulting file ist just a list of lists and various components (a large structure probably describing the PDF in some way).

Printing this to console gives the following output:

$internal
$internal$collections
$internal$collections$addImage_images
$internal$collections$addImage_images$`0`
$internal$collections$addImage_images$`0`$alias
[1] 1916164677

$internal$collections$addImage_images$`0`$w
[1] 1905

$internal$collections$addImage_images$`0`$h
[1] 880

$internal$collections$addImage_images$`0`$cs
[1] "DeviceRGB"

$internal$collections$addImage_images$`0`$bpc
[1] 8

..... And much more......

is there any way to turn this kind of thing into a pdf?

Edit 3:

My half decent solution for anyone interested was to just move the "blob" to Shiny (Shiny.setInputValue)

than use the base64decoder

read image using magick::image_read and write to tempfile pdf using magick::image_write