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
(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)
5. ESC ESC ESC
6. RET (it asks to choose an encoding, chose default raw-text)
Debugger entered--returning value: raw-text
select-safe-coding-system(1 381654 iso-latin-1-dos nil "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww...")
write-region(nil nil "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww...")
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)
Debugger entered--entering a function:
* select-safe-coding-system(1 383892 no-conversion nil)
md5(#<buffer *temp*>)
doc-view--current-cache-dir()
doc-view-already-converted-p()
doc-view-initiate-display()
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)
Debugger entered--returning value: no-conversion
select-safe-coding-system(1 383892 no-conversion nil)
md5(#<buffer *temp*>)
doc-view--current-cache-dir()
doc-view-already-converted-p()
doc-view-initiate-display()
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)
Debugger entered--entering a function:
* select-safe-coding-system("100" nil prefer-utf-8 nil "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww pdf!-2072e1249b26ee28e656f1a01f0cb4a9/resolution.el")
write-region("100" nil "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww pdf!-2072e1249b26ee28e656f1a01f0cb4a9/resolution...." nil silently)
#f(compiled-function () #<bytecode 0x42abe9>)()
doc-view-sentinel(#<process pdf/ps->png> "finished\n")
Debugger entered--returning value: prefer-utf-8-dos
select-safe-coding-system("100" nil prefer-utf-8 nil "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww...")
write-region("100" nil "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww..." nil silently)
#f(compiled-function () #<bytecode 0x42abe9>)()
doc-view-sentinel(#<process pdf/ps->png> "finished\n")
Debugger entered--returning value: prefer-utf-8-dos
select-safe-coding-system("100" nil prefer-utf-8 nil "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww...")
write-region("100" nil "c:/Users/nicho/AppData/Local/Temp/docview1001/!eww..." nil silently)
#f(compiled-function () #<bytecode 0x42abe9>)()
doc-view-sentinel(#<process pdf/ps->png> "finished\n")
Let me know if I was supposed to do something differently.
Nicholas
On Wed, Nov 4, 2020 at 8:07 AM Eli Zaretskii <
eliz@gnu.org> wrote:
> From: Nicholas Harrison <nicholasharrison222@gmail.com>
> Date: Tue, 3 Nov 2020 16:52:40 -0700
> Cc: 44338@debbugs.gnu.org
>
> This can be (partially) corrected by running the following code before the steps 2 and 3:
> (add-to-list 'mailcap-user-mime-data
> '((type . "application/pdf")
> (viewer . doc-view-mode)))
>
> This chooses a view mode for the pdf but that brings the second problem. This selects the default encoding
> of raw-text and the conversion fails:
You say it selects raw-text, but the screenshot you sent clearly shows
that Emacs was trying to use iso-latin-1-dos. In which case the
failure is easily understandable, but I don't immediately see where
did that value come from (it's most probably the default value of
buffer-file-coding-system for you, but since eww-display-pdf binds
coding-system-for-write, the question is why that value isn't being
used). Could you perhaps produce a backtrace from that situation?
For example, like this:
M-: (debug-on-entry 'select-safe-coding-system) RET
and then repeat the recipe.
In any case, this isn't right:
(defun eww-display-pdf ()
(let ((data (buffer-substring (point) (point-max))))
(pop-to-buffer-same-window (get-buffer-create "*eww pdf*"))
(let ((coding-system-for-write 'raw-text) <<<<<<<<<<<<<<<<<<<<<<
(inhibit-read-only t))
(erase-buffer)
(insert data)
(mailcap-view-mime "application/pdf")))
(goto-char (point-min)))
We should use 'raw-text-unix here, since the buffer contents is a
stream of raw bytes.