Add option to control PDF filenames when users download print results through browser preview

[cesarechazu]

Hello
When I try to print a pdf in base64 format the document title does not work.

let opt = {
            "printable": data,
            "type": "pdf",
            "documentTitle": "Test Base64",
            "base64": true
}
printJS(opt);

Thanks for sharing this amazing tool.

[crabbly]

Hi @cesarechazu, that's the expected behavior. As of right now, the document title was intended to be used with HTML, image and JSON prints.

However, I can see that when using base64, you may want to to customize the "filename" used if the user tries to download the print job (a feature provided by some browsers, not a library feature). Is this what you are trying to do?

[cesarechazu]

Hi @crabbly, i have the pdfs stored in base 64 format a postgresql database ... (invoices). So far so good. When the user views the pdf, he wants to download the file with a "human" name, for example: Invoice_001_005.pdf.

With that option "documentTitle" i would avoid saving the pdf to disk

Thanks

[crabbly]

Got it. That's what I thought. Currently, the lib won't use the document title for this. Also, keep in mind that the main purpose for this library is to print. It just happens that users are now trying to download the print results using their browser (the lib doesn't manage downloads, it dispatch print jobs). Firefox for example doesn't even show a preview, therefore, if users are going to primarily download the PDFs, I would recommend just giving them a download button on top of the print button.

That said, here is how we print the base64 data:
https://github.com/crabbly/Print.js/blob/master/src/js/pdf.js#L48

The lib creates a local blob and url, then it sets the iframe src with that url. If the browser (or OS) gives the user an option to save the print job as PDF, it will use the auto generated id / filename in the url. If we could find a way to control this, we could possibly pass the documentTitle string to it and it may work.

I'll try to play with this whenever I have a chance. It would be nice if we could add this feature to the lib. A PR is welcomed :)

[cesarechazu]

@crabbly Thank you very much for your answer, I will save the file to disk and print passing the url.

(A PR is welcomed) Ok, I'll see how I can help

[crabbly]

Ref.:
https://stackoverflow.com/a/52966766
https://stackoverflow.com/questions/44061354/set-the-default-save-as-name-for-a-an-embed-or-iframe-that-uses-a-blob
https://stackoverflow.com/a/41947861

[yannanna0920]

2022年了 这个问题要不要改了

[danielrose7]

A fix for this has been opened in #724 — for PDF iframes, Chrome reads document.title asynchronously after print() returns, so the library now temporarily guards the title with a MutationObserver to keep it stable.

Reference implementation as a standalone helper: https://gist.github.com/danielrose7/adb604b9334118d98de6e856efd043df