RFC implement h4-6 in terminal markdown

[hayd]

Change underlines for h1 to use \equiv

This competes against #10455 and changes the behaviour to (these are bold in the terminal as before):

md"""
#h1
##h2
###h3
####h4
#####h5
######h6"""

 h1
≡≡≡≡

 h2
====

 h3
––––

 h4
----

 h5
⋅⋅⋅⋅

 h6

My objective was to make these obviously ordered. I'd toyed with throwing ∼ and ≃ into the mix but IMO the hierarchy was actually made less clear... but perhaps there are better character(s) to use here?

Note: \cdot isn't quite monospaced in chrome (whatever font github uses in code blocks), but is for me in mac terminal (perhaps this differs from font-to-font?). I'm not sure what the situation is for windows @tkelman (or if this char is supported??)

cc @one-more-minute @peter1000

[tkelman]

\cdot looks okay in default Windows console (I see the same non-monospaced thing in chrome), though ≃ does not, and h3 and h4 are indistinguishable. Is h3 \emdash ?

[hayd]

@tkelman hmmm, I think it's emdash (these were previously the h2 and h3!)
I see the difference as:

[hayd]

@tkelman Ah it wasn't emdash, it was the character before (8211), perhaps it should be emdash! How do these look on Windows:

julia> string(Char(45)) ^ 3
"---"

julia> string(Char(8211)) ^ 3
"–––"

julia> string(Char(8212)) ^ 3
"———"

[tkelman]

pretty much identical, unfortunately

[hayd]

It's frustrating that the bit which doesn't work/isn't distinct is the bit already in master, I wasn't expecting that! Another option was with \sim and \simeq, something like:

(I wasn't as much a fan of this... maybe we should use €.)

[tkelman]

simeq is just a question mark. Regular dash looks distinct from emdash when using a better font, but that takes some extra fiddling to set up. 8211 and 8212 look the same though, in Deja Vu Sans Mono.

[hayd]

Yep, 8211 and 8212 are the same for me too (I was just hoping they were different for you, and that might have corrected your problem). I think that rules out simeq.

Is requiring a "good" font that distinguishes h3 (emdash) and h4 (regular dash) a problem?

[hayd]

rebased over merge conflict.

Just to summarize where we're at:

Before (in master): if you have a bad font, h2 and h3 may be indistinguishable.
With this PR: If you have a bad font, h3 and h4 may be indistinguishable.

cc @StefanKarpinski (who commented about this in the other PR)

IMO if you have a bad font some things aren't going to display at all (e.g. \sim), so users should be encouraged to use a "good font" during/post-installation... Not being able to distinguish h3 and h4 is a relatively minor inconvenience to useful characters not rendering at all.

[hayd]

@one-more-minute bump! (last one)

[MikeInnes]

Alright, looking forward to seeing your other changes! FWIW, I have a couple of freer weeks coming up, so I should be able to review things a bit more quickly then.

[hayd]

awesome, thanks!

[peter1000]

@hayd

just a question: is h6 supposed to look different from bold or did you settle in the end for just bold.

At least I can not see any difference.. except extra indentation - but all togehter very nice indeed

[hayd]

@peter1000 it's spaced, bold and newline, not sure I'm fully happy with that (but kinda ran out of characters which make sense!... a full-width = as h2 would have perfectly made this up to 6, unfortunately it doesn't exist). I thinking seeing this in some real world examples will confirm whether it makes sense.

Thanks for driving this change, is certainly a big improvement from before.

[peter1000]

I think there is one to many new line for h6: I know it fits the underlines of the others but it looks bit strange (at least to me).

I think the indentation and the Bold would be good enough. (but this is just my opinon)
For spaced I can not see a difference but maybe it depends also on the fonts.

using Base.Markdown

md"""
#h1
test
##h2
test
###h3
test
####h4
test
#####h5
test
######Bold
test
#h1
test
##h2
test
###h3
test
####h4
test
#####h5
test
######h6
test

**h6**    only Bold

"""

[hayd]

I agree, one new line is better for h6 (I was being lazy not implementing it, I have a one line fix: changing this line to char != ' ' && println(...).

(The spaced thing is indeed about fonts, these look fine on monospaced fonts, everyone should be using a monospaced font! :) )

 not monospaced (in github's font)
⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅

[peter1000]

I think you might want to merge your one line fix: changing this line to char != ' ' && println(...).
so that this is final.

Anyway looks great so much better than before.

[hayd]

@peter1000 including that as a commit in #10626.