On Sat, 09 Feb 2019 00:16:30 +0200 Eli Zaretskii via Unicode <[email protected]> wrote:
> > Date: Fri, 8 Feb 2019 21:55:58 +0000 > > From: Richard Wordingham via Unicode <[email protected]> > > I will give a concrete application. If I want to make a font that > > is interpretable for Tai Tham and maximally usable with VTE, what > > are the VTE-specific constraints for me to be able to use it for > > Tai Tham when using basic text utilities? For example, if VTE > > decides that for <cons, left-matra, above-matra> as two clusters > > <cons> and <left-matra, above-matra>, can I nevertheless position > > the above-matra above the <cons>? > For character composition, you must have a shaping engine to talk to, > and the shaper should tell you the width of each grapheme cluster it > returns. (a) What defines the grapheme clusters? The definition might be terminal-specific. (b) With a terminal that expects a fixed width font, surely the terminal decides how many cells it allocates to a group of characters, and the font designer has to come up with a suitable value based on that. > I don't see how you can expect wcwidth, or any other > interface that was designed to work with _characters_, to be useful > when you need to display grapheme clusters. Well I can envisage a decision being made that a grapheme cluster str (as decreed by the terminal) shall occupy wcswidth(str) cells - "The wcswidth() function returns the number of column positions for the wide-character string s, truncated to at most length n". Richard.
