[issue20359] Having escape sequences (like color codes) in the sys.ps1 messes up readline's input line calculations

[Steve]

Steve added the comment:

Hi Georg,

Thanks again for the responses and your help. After a bit of research, I discovered the /reasons/ behind needing the \001 and \002 escapes. Thought I'd log the links here for posterity sake:

  - To color something in on a color capable terminal console you just need to use the "\033[<color code>m" escape sequence. This would be sufficient[1]
  - However readline messes up the line width calculation because it measures the escape sequences as a characters too. To avoid this you have to wrap the escape sequences within \001 and \002.[2]
  - On some terminal applications (like the one I am using - terminator[3]), if you add the \001 and \002 escapes to color text which is *not* interpreted by readline, (for instance if you have a single function to color text and you want to use it to color both your sys.ps1 and output text), the \001 and \002 codes will get printed out using a representation (like a unicode 'box'[4]). So, one would have to workaround that in the text coloring function.

[1] http://en.wikipedia.org/wiki/ANSI_escape_code#Colors
[2] bugs.python.org/issue17337/ and
    http://stackoverflow.com/questions/9468435/look-how-to-fix-column-calculation-in-python-readline-if-use-color-prompt
[3] http://gnometerminator.blogspot.sg/p/introduction.html
[4] http://en.wikipedia.org/wiki/Control_character#Display

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<http://bugs.python.org/issue20359>
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