Adjust letterspacing for a portion of the text

#1

Is it possible to adjust the letterspacing of the text for a specific portion of the text?

#2

I do not think so. What is the purpose?

#3

It may be desirable in some cases to adjust the letterspacing (or tracking) of text when the defaults are not correct. One common example is strings of capitals or small-caps. It’s always recommended that strings of capitals are letterspaced 5% or 10% wider than normal text (see for example R. Bringhurst “Elements of Typographic Style”).

All software allows for this, even Ms Word, so I think it should be added in TeXmacs.

#4

I remember this mentioned in Mogan’s TODOs for CJK @darcy correct me if not

#5

There must be some low level macro or command to do this, right? What controls letterspacing in TeXmacs normally?

#6

I’m adjusting the spacing between the CJK characters and the English words.

#7

I’ve checked the source code but there seems not to be any tunable parameter to modify the default letter spacing (which is a font-related parameter). TeXmacs does some tuning, but seems only related to other kind of spaces. See e.g. src/Graphics/Fonts/font_spacing.cpp . I guess would not be difficult to add, but there is not right now. I agree that we maybe can add an environment parameter to control a multiplier to the spacing. How LaTeX implement this?

#8

In LaTeX this is done with \textls{} which I believe is part of the microtype package.

You are correct, letterspacing is part of the font informaton (along with kerning), but TeXmacs must deal with it during the line-breaking process. I.e. slightly adjust the space between letters to optimize the line-breaking processes. In fact, the threshold to which this is allowed is adjustable in Format > Paragraph > Advanced or Document > Paragraph > Advanced.

So it should be relatively easy to add the feature to manually adjust letterspacing.