Printing the hidden canvas of PDF.js viewer

[Simon Males]

Hello,

I am really interested in printing PDFs across devices. I really like viewer.html printing experience. To me it is amazing that no document metadata is included in the print output.

Up until today, I have being experimenting with printing PDFs within Iframes though it has proven difficult on Firefox, Internet Explorer and Android browsers.

I would like to silently render the PDF.js viewer within a document and trigger a print job on it.

>From what I can tell viewer.js assumes that the document doesn't include anything else.

Interested to know if other people are using PDF.js for printing.

[Simon Males]

This is pretty complex for me at the moment, I still cannot entirely see how canvas printing hides page metadata from the print out.

Then I uncovered this gem from the original proposal: "Using CSS it's possible to make one canvas element take up one physical page and then precisely layout content on the canvas." https://etherpad.mozilla.org/printCallbackSpec

I would love to see a reduced example of this, I fail to see in PDF.js how this is actually achieved.

[ydel...@mozilla.com]

On Monday, June 15, 2015 at 11:22:54 AM UTC-5, Simon Males wrote:
> Then I uncovered this gem from the original proposal: "Using CSS it's possible to make one canvas element take up one physical page and then precisely layout content on the canvas." https://etherpad.mozilla.org/printCallbackSpec
>
> I would love to see a reduced example of this, I fail to see in PDF.js how this is actually achieved.

The mozPrintCallback was implemented at https://bugzilla.mozilla.org/show_bug.cgi?id=745025 . You can find its usage in PDF.js at the https://github.com/mozilla/pdf.js/blob/c8fd9c8c06cf14ff2203a089f17c881dcdb9ca10/web/pdf_page_view.js#L519 -- the callback is invoked during printing and an argument with device-specific 2d context is passed to it. When painting is done the callee must invoke the done method to complete the asynchronous operation.

See also https://bugzilla.mozilla.org/show_bug.cgi?id=743252 about moznomarginboxes, which hides a URL and page numbers from the printed material.

Thanks.

[Simon Males]

Interesting thank you!

So it looks like for cross browser support @page { margin: 0; } is required.