calibre viewer css file?

[neo1]

Calibre -> Preferences -> Styles

leads to the viewer custom css file configuration. Using this
interface to edit the css file is a huge pain point. It is MUCH easier
to use a proper file editor on the local system. I can not
find a file one can edit on the local system that would have the same
effect. Am I missing something?

The file viewer-webengine.json in CALIBRE_CONFIG_DIRECTORY stores this
css style sheet inside the user_stylesheet variable. Changing the
style sheet there has the desired effect. The below bash script
(Linux) automates this task. It's basically a one liner. You
edit a local file in your favorite editor then inject it into
viewer-webengine.json.

NOTE: calibre viewer should be closed doing this, or it doesn't work.

#!/bin/bash
###
# set these accordingly
MYFILE=$HOME/calibre.css
CALIBRE_CONFIG_DIRECTORY=$HOME/.config/calibre
###

config_file=$CALIBRE_CONFIG_DIRECTORY/viewer-webengine.json
tmp=$(mktemp) # create a temporary file
jq --arg val "$(<"$MYFILE")" '."session_data"."user_stylesheet" = $val' "$config_file" >"$tmp" && mv "$tmp" "$config_file"

[neo1]

The last two lines in my previous post, is really one line that got
cut off. So much for trying to post code.

Here's a link to a proper write up that containing a link to the file with the
code along with an explanation.
link

Here's a link to the shell script file
file

[DNSB]

Code should be wrapped in [CODE][/CODE] (the # tool)...

#!/bin/sh
###
# set these accordingly
CSS_FILE=$HOME/calibre.css
CALIBRE_CONFIG_DIRECTORY=$HOME/.config/calibre
###

config_file=$CALIBRE_CONFIG_DIRECTORY/viewer-webengine.json
tmp=$(mktemp) # create a temporary file
jq --arg val "$(cat "$CSS_FILE")" '."session_data"."user_stylesheet" = $val' "$config_file" >"$tmp" && mv "$tmp" "$config_file"

--arg val "$(cat "$CSS_FILE")" : sets the variable val to the contents of $CSS_FILE

'."session_data"."user_stylesheet" = $val' : jq program to run. It assigns the variable "session_data"."user_stylesheet" to the value of the variable val, i.e. the contents of $CSS_FILE

"$config_file" : is the source file

> "$tmp" : send the output of jq to a temporary file

&& mv "$tmp" "$config_file" : and if all goes well replace the original with the temporary file