Unicode Box Drawing characters not printed in Ruby

Question

I work on a game in Ruby. It uses ncurses to draw window contents and refresh the screen. This all works fine on macOS, where I develop the stuff. But on Linux, I cannot get any

Answer 1

Actually this should be several questions, but the most recent one asks how the characters could be shown as double-width.

The screenshot does not match the given example program. That only draws a few sample characters, while the screenshot shows boxes.

However, the particular line-drawing characters can be the problem, versus the locale tables (and depending on the actual program used). That's because those codes are ambiguous width (see U+2550). The standard leaves it up to the implementer whether to treat them as single-width or double-width. Not everyone agrees on the actual width.

If this were a bug report, I'd get the actual program source to test with, but suspect the problem lies in Ruby.