This experiment fails, but there are some interesting tips in discuss.
So I propose little bit different proposal - choose one predefined style for any table lines elements. These styles are active only when "linestyle" is unicode.
So possible line elements are:
* border,
* header_separator,
* row_separator,
* column_separator,
Possible styles (for each element)
* none,
* single,
* double,
* thick,
It should to have enough variability to define all styles proposed early. I hope, so this proposal is secure and simple for usage. Styles should be persistently saved in .psqlrc file - and some examples can be in documentation.
Usage:
\pset linestyle_border double
\pset linestyle_header_separator single
\pset linestyle_row_separator single
\pset linestyle_column_separator single
\pset linestyle unicode
╔═══╤════════════╤═══════╗
║ a │ b │ c ║
╟───┼────────────┼───────╢
║ 1 │ 2012-05-24 │ Hello ║
╟───┼────────────┼───────╢
║ 2 │ 2012-05-25 │ Hello ║
║ │ │ World ║
╚═══╧════════════╧═══════╝
(2 rows)
