Re: Performance degradation from long lines

[Eli Zaretskii]

> From: Clément Pit-Claudel <address@hidden>
> Date: Thu, 25 Oct 2018 13:53:20 -0400
> 
> * bold, italics, and other important face attributes
> * Some characters are not covered by fixed-pitch fonts, so they cannot be 
> displayed. The usual box-with-hex-code display of such characters will also 
> be lost, so we will be left with displaying them as ? or somesuch.
> * Character composition will also be lost, so bye-bye prettify-symbols-mode 
> and support for some scripts that cannot be displayed without composed 
> characters.
> * Some characters (mostly from East-Asian scripts) need to be displayed at 
> twice the width, so either you give up those scripts, or you are back to the 
> original problem.
> 
> Many (all?) of these features are available in the terminal, too (at least 
> the following: bold, underline, italics, characters that don't have 
> fixed-pitched fonts, prettify-symbols-mode, and wide characters).  What did 
> you mean by "terminal Emacs doesn't have those capabilities in the first 
> place"?

Character attributes (bold, italics) on a TTY don't affect the size of
the characters.  The box-with-hex-code and character composition are
not available on a TTY.  Wide characters _are_ available, but they
count as 2 characters, so again they don't affect the metrics.
Prettify-symbols-mode will only work if the replacement is a single
character, not a composition of several characters in the same cell.