> From: Nicholas Harrison <nicholasharrison222@gmail.com>
> Date: Wed, 4 Nov 2020 16:43:13 -0700
> Cc: "Basil L. Contovounesios" <contovob@tcd.ie>, 44338@debbugs.gnu.org
>
> Not sure if this is much help, but here is the backtrace given when I do the following steps:
>
> 1. emacs -Q
> 2. M-: (debug-on-entry 'select-safe-coding-system) RET
> 3. M-x eww RET https://www.gnu.org/software/emacs/manual/pdf/emacs-xtra.pdf RET
> (no backtrace here)
> 4. M-x doc-view-mode RET
>
> Debugger entered--entering a function:
> * select-safe-coding-system(1 381654 iso-latin-1-dos nil
> "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww pdf!")
> write-region(nil nil "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww pdf!")
> doc-view-mode()
> funcall-interactively(doc-view-mode)
> call-interactively(doc-view-mode record nil)
> command-execute(doc-view-mode record)
> execute-extended-command(nil "doc-view-mode" "doc-view-mo")
> funcall-interactively(execute-extended-command nil "doc-view-mode" "doc-view-mo")
> call-interactively(execute-extended-command nil nil)
> command-execute(execute-extended-command)
Thanks. This tells part of the story, but not all of it. What I
wanted to see was the backtrace when doc-view-mode is invoked by EWW.
AFAIU, that requires you to augment mailcap-user-mime-data as this:
(add-to-list 'mailcap-user-mime-data
'((type . "application/pdf")
(viewer . doc-view-mode)))
before performing the reproduction steps.
To give you more background: when you invoke doc-view-mode manually in
a buffer produced by "M-x eww", the buffer's buffer-file-coding-system
is the platform default, in your case iso-latin-1-dos. That is what
doc-view-mode uses to write the PDF bytestream to a temporary file,
and that fails because iso-latin-1-dos cannot encode the raw bytes in
the binary content. But eww-display-pdf binds coding-system-for-write
to 'raw-text, and then doc-view-mode ought to use that to write to the
temporary file, and yet in your screenshot I still see it tried to use
iso-latin-1-dos, which I cannot explain. So I'd like to see the
backtrace when you invoke doc-view-mode via EWW, after augmenting
mailcap-user-mime-data, to try to understand why it uses the wrong
encoding.
Can you please produce the backtrace under those modified conditions?