Mfcttrf

I am encountering some weird behavior and errors when manipulating strings inside of lettrine arguments: the code either doesn't compile or produces unexpected results. On top of that, it is font-related, e.g., some things work with regular fonts, but fail with some other fonts, such as most of fonts here: https://tug.org/FontCatalogue/otherfonts.html#initials

Any insight into this issue and advice on how one could fix this would be highly appreciated!

Here is a typical example:

documentclassarticle

usepackagetimes,lettrine,Eileen,coolstr,stringstrings,xstring

%renewcommand*LettrineFontHookEileenfamily %%% Eileen fancy drop letter WTF?

newcommand*first[1]substring#111 %%% stringstrings version
%newcommand*first[1]substr#111 %%% coolstr version DOES NOT WORK AT ALL
%newcommand*first[1]StrLeft#11 %%% xstring version DOES NOT WORK AT ALL

begindocument


lettrinefirstWhaaathat the duck? %%% DOES NOT WORK AS INTENDED WITH EILEEN

vspace3em

lettrinefirstWhathat the duck? %%% DOES NOT WORK AT ALL WITH EILEEN

enddocument

I recommend, in a case like this, doing it with raw TeX, without parsing packages.

documentclassarticle
usepackagetimes,lettrine,Eileen
deffirstaux#1#2relax#1#2
newcommandflettrine[1]expandafterlettrinefirstaux#1relax
begindocument
flettrineWhat the duck?bigskip

renewcommand*LettrineFontHookEileenfamily
flettrineWhat the duck?
enddocument

If you wanted to use stringstrings for other reasons (more complex manipulations, for example), I would use substring to store the result in thestring, and then pass thestring on to lettrine, in this fashion:

documentclassarticle
usepackagetimes,lettrine,Eileen,coolstr,stringstrings,xstring
newcommand*first[1]substring[q]#111 %%% stringstrings version
newcommandflettrine[2]first#1lettrinethestring#2
begindocument
flettrineWhaaathat the duck? %%% DOES NOT WORK AS INTENDED WITH EILEEN

vspace3em
renewcommand*LettrineFontHookEileenfamily %%% Eileen fancy drop letter WTF?

flettrineWhathat the duck? %%% DOES NOT WORK AT ALL WITH EILEEN
enddocument

With expl3 it's really easy:

documentclassarticle

usepackagenewtxtext,lettrine,Eileen,xparse

renewcommand*LettrineFontHookEileenfamily %%% Eileen fancy drop letter WTF?

ExplSyntaxOn
NewDocumentCommandIiroLettrineOm
 
 lettrine[#1]tl_range:nnn #2 1 1 tl_range:nnn #2 2 -1 
 
ExplSyntaxOff

begindocument

IiroLettrineWhat the duck?

enddocument

The problem with your code is that StrLeft#11 doesn't produce the first letter, but the set of instructions for printing it, but lettrine wants just a letter (after expansion).

The tl_range:nnn function is fully expandable, so it makes no problem to lettrine. With tl_range:nnn #1 1 1 the first item in the argument is delivered; with tl_range:nnn #1 2 -1 the remaining items are produced (the negative second number means “up to the last item”).

Since small caps are needed, it's better to use newtxtext that provides real small caps, instead of the faked ones you get with times.

You can do it also with xstring, using its trailing optional argument feature:

documentclassarticle

usepackagenewtxtext,lettrine,Eileen,xstring

renewcommand*LettrineFontHookEileenfamily %%% Eileen fancy drop letter WTF?

newcommandIiroLettrine[2][]%
 StrLeft#21[firstletter]%
 StrGobbleLeft#21[otherletters]%
 lettrine[#1]firstletterotherletters%
 

begindocument

IiroLettrineWhat the duck?

enddocument

In both cases I kept the optional argument to lettrine available in IiroLettrine.