missing interface functions for an IO

[vtjnash]

The typical interface functions for an IO are most clearly reflected by the forwarding methods provided by AbstractPipe:
https://github.com/JuliaLang/julia/blob/17cfb8e65ead377bf1b4598d8a9869144142c84e/base/io.jl#L414-L443

in particular, this method seems to be missing, and typically is the primary method that makes something an "IO" subtype

unsafe_write(io::AbstractPipe, p::Ptr{UInt8}, nb::UInt) 

[timholy]

I wondered about implementing that. But one thing this package absolutely must do is ensure that any terminal-escapes get "closed": you don't want to truncate

julia> sprint("abcdef"; context=:color=>true) do io, str
           printstyled(io, str; color=:red)
       end
"\e[31mabcdef\e[39m"

before the color gets restored to default at the end. (As stated in the README, it gets truncated to "\e[31mabcd…\e[39m" if your width limit is 5.)

My thinking was that if I live in just the world of Chars, then I have a better change of understanding how to interpret what I'm getting than if I delve into Ptr{UInt8}. Whether I was correct or not, the omission was deliberate.

However, I guess I could implement it to interpret it as a String, and do Char level processing on the string. Would that be better than intercepting dispatch at a higher level, as done here?

[timholy]

I guess the other reason not to implement it: TextWidthLimiter is only about text; one should not be able to write binary data to it.

[timholy]

More generally, I'm wondering if we want an abstract type TextIO <: IO end type that only supports text IO. There seem to be many applications. For example, for JuliaLang/julia#48444 (comment) I plan to create a TypeTreeIO <: TextIO object that adds children on encountering '{', ',', or '}'.