prompt strings with non-ansi escape sequences

[p...@bothner.com]

I request a mechanism for JLine3 to emit uninterpreted escape sequences in prompt

strings, as well as delimiting highlighted tokens.  Specifically, I suggest extending

the syntax of the readLine prompt and the secondary-prompt-pattern with zsh-style

"%{xxx%}" delimiters: The text "xxx" is emitted, but not interpreted by jline.

Jline already supports AttributedStrings, and prompt strings can contain the common

ansi/xterm highlighting and colors.  However, I need to go beyond this.

For both prompt strings and highlighting it can be desirable to mark sections of the text with

more high-level "semantic" properties, such as "prompt" or "string-literal", rather than just

low-level "presentation" properties, such as "blue" or "bold".  The DomTerm terminal emulator

(see https://groups.google.com/forum/#!topic/jline-users/xCT9oug7vOQ and http://domterm.org)

supports putting text inside spans with various attributes; various escape sequences are

available for this, including ones for variable kinds of prompts.  I don't propose that jline

know about these escape sequences; just that jline be able to emit them.

There would be an compatibility break with existing code, since we'd change the readLine prompt

to a template containing "%{...%}" (and %%) - these would no longer be literal text.  But

such prompts are rare (non-existent?), and before jline3 is released is a good time to

make this change.  (We could continue with the existing methods taking literal promps,

and add new ones that take templates, but that seems excessive.)

To implement this feature the AttributedString class needs to be more extensible.

The simplest mechanism I can think of is to define a new AttributedStyle.GENERIC_ESCAPE

object, along with a corresponding F_GENERIC_ESCAPE int style value.  Any characters with the

F_GENERIC_ESCAPE style are considered to take 0 columns, and are printed as-is

with no interpretation. Translating a prompt pattern containing %{xxx%} would just be a

matter of xxx with the F_GENERIC_ESCAPE style.

I assume there are some complications with this idea, but I'm willing to try implementing

it if you think it makes sense.

[Guillaume Nodet]

The idea sounds good to me.

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