Print options preclude the use of pagedown

[eamcvey]

It would be quite useful to be able to print a flexdashboard to pdf as a backup method to provide the content to people.

Per this issue, https://github.com/rstudio/pagedown/issues/229, this doesn't work currently with pagedown/Chrome print and flexdashboards due to the print CSS rules in bootstrap:

@media print { *, *:before, *:after { background: transparent !important; color: #000 !important; -webkit-box-shadow: none !important; box-shadow: none !important; text-shadow: none !important; } }

Perhaps these are important for other reasons, but if there were at least an easy option in flexdashboard to override them, it would be lovely. I have evidence that I'm not the only one who would be interested in this capability.

[cpsievert]

Bootstrap's print rules aren't the (main) issue here. There's at least two other issues at play:

1. vertical_layout: fill doesn't work in the way it probably should in print because these rules probably need to also be applied for print

https://github.com/rstudio/flexdashboard/blob/master/inst/www/flex_dashboard/fillpage.css

2. A larger, more troubling, issue is that it appears Chrome's print utility is unable to properly render a base64 encoded background on a <p> tag, but this is how flexdashboard renders static images. For a minimal reprex, note that this image renders in Chrome fine, but it doesn't for print:

library(htmltools)

uri <- base64enc::dataURI(file = "https://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/R_logo.svg/2560px-R_logo.svg.png")
browsable(tags$body(
  style = "height:100%; width:100%",
  tags$p(
    style = sprintf("background: url('%s') center center / contain no-repeat;", uri),
    style = "position:absolute; top:0; left:0; right:0; bottom:0; margin: 0;"
  )
))

[RLesur]

A larger, more troubling, issue is that it appears Chrome's print utility is unable to properly render a base64 encoded background on a <p> tag

More precisely, Chrome is able to render a base64 background image but this option is disabled by default. In the Chrome print dialog box, one has to check the option "Background graphics". The pagedown::chrome_print() function modifies Chrome's default behavior and prints background by default (see here)

[gadenbuie]

If we added print styles to flexdashboard, would it be better to faithfully reproduce one state of the dashboard? Or would we try to switch to a "show everything" approach where we attempt to ensure all pages and tabs are visible and flow in the page? (I'd advocate for the second option.)