Subject: bug#23930: 25.0.95; "M-: 3072 RET" very slow to echo "3072 (#o6000, #xc00)"

From: Eli Zaretskii <[email-masked]>
Date: Sun, 10 Jul 2016 05:38:36 +0300

> From: Richard Copley <[email-masked]>
> Date: Sat, 9 Jul 2016 22:32:43 +0100
> 
> Recipe from 'emacs -Q':
>   M-: 3072 RET
> 
> This has the result of echoing "3072 (#o6000, #xc00)", but there's a
> pause of around 8 seconds before the result is echoed. The long wait
> is the bug I'm reporting.

It looks for a font to display the codepoint.

> Forgive me if this is hopelessly naive, but as we're only looking for
> one {character or whatever}, is there room to optimize by memoizing
> the corresponding {whatever} in each codepage, and using it while we're
> searching the font files?

It's Windows that does this, not us.  Emacs just tries all the fonts
it can, looking for the character, until it gives up.