bug#57693: 29.0.50; Is there a more reliable version of `char-displayable-p'?

[Ihor Radchenko]

Stefan Kangas <stefankangas@gmail.com> writes:

> I know very little about this area of Emacs, but is there any reason why
> we couldn't just (try to) make `char-displayable-p' more accurate?
>
> I'm not asking for a perfect solution, but even just making it a bit
> better might be a step forward.

>From the docstring:

>> On a multi-font display, the test is only whether there is an
>> appropriate font from the selected frame's fontset to display
>> CHAR's charset in general.  Since fonts may be specified on a
>> per-character basis, this may not be accurate.

The actual font used to display char in specific buffer at specific
position may depend on various buffer-local settings, property
inheritance, and fontification (possibly modified by user). As Eli
pointed, the most accurate way to check if character can be displayed
involves trying to insert it first, letting the display engine do its
job, and checking what is the result.

-- 
Ihor Radchenko,
Org mode contributor,
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