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More specifically, in Vim if I press escape twice (and under some other circumstances too) I get this character appearing:

It can be replicated by typing echo, then Ctrl-V, then escape

Here's what it looks like:

terminal output

I've tried changing the font and TERM setting, neither of which make a difference. No other terminals I've tried (xterm, urxvt, that KDE console) have the same behaviour.

What I'd like to know is whether this is a bug or intended behaviour, and if there's any workarounds

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On a related note, for anyone who is having the same issue with Vim, the cause is the visualbell setting. Placing set novisualbell in the vimrc seems to sort it – benwh Sep 3 '12 at 22:45
up vote 2 down vote accepted

It's intended behavior. No typeface provides a glyph for that codepoint, so the font engine generates the default "codepoint-in-a-box" glyph.

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So the intended behaviour of all of the other terminal applications is to suppress it? – benwh Sep 3 '12 at 10:40
They use a different font engine. – Ignacio Vazquez-Abrams Sep 3 '12 at 10:44
@benwh: I'm not sure if there's even an "intended behavior" for this specific character. ESC is the first byte of all "escape sequences" that control the terminal's behavior (move cursor, set colors, etc) – so technically, when a program outputs a bare ESC, the terminal sees it as an invalid escape sequence and can choose to print it out, or to discard it. – grawity Sep 3 '12 at 10:47
how come all of the other terminal emulators know what to do with it? – Quinn Wilson Nov 29 '14 at 22:48
@QuinnWilson: They don't. They simply don't display anything since that's the behavior of their font engines. – Ignacio Vazquez-Abrams Nov 29 '14 at 22:51

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