bug#41278: 27.0.91; incorrect U+203E OVERLINE alignment with Fantasque Sans Mono

[Vincent Lefevre]

On 2020-05-15 13:57:39 +0200, Vincent Lefevre wrote:
> On 2020-05-15 14:25:03 +0300, Eli Zaretskii wrote:
> > If not, you will always see alignment in xterm, but not always in
> > Emacs.
> 
> I think that if the main font is a monospaced font, Emacs should
> honor this choice in font replacements, keeping the cell dimensions
> of the main font.
> 
> Now, this would solve the alignment problem, but if Emacs just does
> that using the current font replacement, there will still be a space
> between the U+203E OVERLINE characters. This issue does not occur
> with xterm.

BTW, Noto Mono is also affected by font replacements that don't match
the cell width of the main font, both for U+203E OVERLINE and for
box drawing characters.

Some tests can be done with Markus Kuhn's demo file at
  https://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-demo.txt

In particular:

Box drawing alignment tests:                                          █
                                                                      ▉
  ╔══╦══╗  ┌──┬──┐  ╭──┬──╮  ╭──┬──╮  ┏━━┳━━┓  ┎┒┏┑   ╷  ╻ ┏┯┓ ┌┰┐    ▊ ╱╲╱╲╳╳╳
  ║┌─╨─┐║  │╔═╧═╗│  │╒═╪═╕│  │╓─╁─╖│  ┃┌─╂─┐┃  ┗╃╄┙  ╶┼╴╺╋╸┠┼┨ ┝╋┥    ▋ ╲╱╲╱╳╳╳
  ║│╲ ╱│║  │║   ║│  ││ │ ││  │║ ┃ ║│  ┃│ ╿ │┃  ┍╅╆┓   ╵  ╹ ┗┷┛ └┸┘    ▌ ╱╲╱╲╳╳╳
  ╠╡ ╳ ╞╣  ├╢   ╟┤  ├┼─┼─┼┤  ├╫─╂─╫┤  ┣┿╾┼╼┿┫  ┕┛┖┚     ┌┄┄┐ ╎ ┏┅┅┓ ┋ ▍ ╲╱╲╱╳╳╳
  ║│╱ ╲│║  │║   ║│  ││ │ ││  │║ ┃ ║│  ┃│ ╽ │┃  ░░▒▒▓▓██ ┊  ┆ ╎ ╏  ┇ ┋ ▎
  ║└─╥─┘║  │╚═╤═╝│  │╘═╪═╛│  │╙─╀─╜│  ┃└─╂─┘┃  ░░▒▒▓▓██ ┊  ┆ ╎ ╏  ┇ ┋ ▏
  ╚══╩══╝  └──┴──┘  ╰──┴──╯  ╰──┴──╯  ┗━━┻━━┛  ▗▄▖▛▀▜   └╌╌┘ ╎ ┗╍╍┛ ┋  ▁▂▃▄▅▆▇█
                                               ▝▀▘▙▄▟

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)