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                  Quirky TidBITS Issue Printing Problem Solved

   Adam Engst

   It's uncommon for people to want to print TidBITS issues, so I was
   surprised when Lauri Reinhardt, who helps us with support, forwarded me
   a message from a reader asking if there was a way to print the email
   issue of TidBITS with all the images. Neither of us had ever tried to
   do such a thing, but the reader was entirely correct: printing a
   TidBITS issue or exporting it to PDF resulted in blank boxes in place
   of the images.
   TidBITS#1648 in PDF in Preview'no images are loading

   Tinkering with Mail's Protect Mail Activity setting made no difference,
   and the images showed up fine in the message itself'it wasn't related
   to loading remote content. Even more confusing was the fact that
   [1]Mimestream, which I use with Gmail, suffered from the same problem,
   but only in macOS 12 Monterey, not in macOS 13 Ventura. Printing from
   Gmail's Web interface also worked fine.

   A look at the raw source of our issues revealed a smoking gun right
   away: a loading="lazy" attribute for every IMG tag in articles. The
   sponsor banners at the top of the issue lacked that attribute, and they
   appeared in PDFs fine. Curious, I turned to Mimestream's developer,
   Neil Jhaveri, who used to work on Mail at Apple. He said that Mail
   generates an offscreen web view, waits for the 'load' part of the
   document to arrive, and then 'prints.' But loading="lazy" causes images
   to load only when scrolled into view, which never happens with
   printing. Mimestream shared the problem, at least in Monterey, because
   it uses WebKit for printing, just like Mail. Neil recommended dropping
   the loading="lazy" attribute because he didn't think images (at least
   those with width and height attributes) would block the page from
   rendering until loaded anyway.

   During these conversations, Lauri stumbled upon a workaround that makes
   sense in the context of Neil's explanation. She postulated that perhaps
   the images were too large to load, so she tried shrinking them with the
   Scaling option in the Print dialog, which caused at least some images
   to display. I did testing and found that if I changed the scaling
   percentage to 99%, some images would load'but they'd be fuzzy'and
   others would remain blank. However, if I changed the scaling percentage
   more seriously, such as to 87%, and then scrolled through the entire
   document preview, all images would appear crisply in the resulting PDF,
   even if I later returned the scaling to 100%. Presumably, asking the
   Print dialog to scale the output forced WebKit to load all the images,
   allowing them to appear.

   When I asked our developer Eli Van Zoeren to remove that loading="lazy"
   attribute from the IMG tags, he noted that WordPress inserted it
   automatically, so he added a filter to remove it from the email
   versions of our issues. (His code adds the sponsor banners to the issue
   separately, which is why they lack that attribute.) I was excited to
   test the fix with the next week's issue, only to be disappointed to
   discover that the problem hadn't gone away. It turned out that, after
   Eli filtered out loading="lazy", WordPress replaced it with a
   similar-sounding attribute decoding="async". After another round of
   Whack-an-Attribute, the problem disappeared for good.
   TidBITS#1649 in PDF in Preview'images have loaded properly

   So, while I don't recommend printing TidBITS issues'we don't format
   them for print, and they'll consume quite a bit of paper'you'll at
   least see the images now. Interestingly, both screenshots above have
   extra blank pages at the end. I don't know why Mail adds them, but I
   recommend removing them. Choose File > Export to PDF, open the file in
   Preview, select the blank pages (and any other unnecessary pages) in
   the sidebar, and delete them before printing.

   I very much doubt that many people were affected by this problem, but
   at least one TidBITS reader will be happier, and with luck, others who
   run into a similar problem will find this article and figure out how to
   solve it more quickly.

References

   Visible links
   1. https://mimestream.com/

   Hidden links:
   2. https://tidbits.com/wp/../uploads/2023/03/Printing-problem-1648.png
   3. https://tidbits.com/wp/../uploads/2023/03/Printing-problem-scaling-workaround.png
   4. https://tidbits.com/wp/../uploads/2023/03/Printing-problem-1649.png

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