bug#36454: 26.2.90; feature request - Insert char by hex tab completion or C-x 8 RET ffe <TAB>

[Drew Adams]

> > You don't need to distinguish them.  You don't
> > care which part matches "ffe" or "20".  You
> > don't even care if both name and code point
> > should happen to match the same pattern.  All
> > you care about is being able to match the info
> > about the char: its name or code point.
> 
> So, after I type "ffe" and press TAB, it should look through names and
> codes at the same time, and present completion candidates for both at
> the same time, for example I'll get "￪ ffea" and "GIRAFFE FACE" in the
> same window above?
> 
> Because, if yes, then user may get a lot of results, as it was pointed
> out before.

Have you tried it?

No, you won't get lots of results.  There's little overlap
in general, even if you type only a few chars.  Certainly
less than you get with function and variable names,
especially those that have common prefixes.

You'll typically type little to get to a single candidate.

Completion of `ffe' gives this (using Emacs 23 for this;
no GIRAFFE):
____

DIFFERENCE BETWEEN      224F    ≏                               
FULLWIDTH BROKEN BAR    FFE4    ￤                              
FULLWIDTH BROKEN VERTICAL BAR   FFE4    ￤                      
FULLWIDTH CENT SIGN     FFE0    ￠                              
FULLWIDTH MACRON        FFE3    ￣                              
FULLWIDTH NOT SIGN      FFE2    ￢                              
FULLWIDTH POUND SIGN    FFE1    ￡                              
FULLWIDTH SPACING MACRON        FFE3    ￣                      
FULLWIDTH WON SIGN      FFE6    ￦                              
FULLWIDTH YEN SIGN      FFE5    ￥                              
GREEK DASIA     1FFE    ῾                                       
HALFWIDTH BLACK SQUARE  FFED    ￭                               
HALFWIDTH DOWNWARDS ARROW       FFEC    ￬                       
HALFWIDTH FORMS LIGHT VERTICAL  FFE8    ￨                       
HALFWIDTH LEFTWARDS ARROW       FFE9    ￩                       
HALFWIDTH RIGHTWARDS ARROW      FFEB    ￫                       
HALFWIDTH UPWARDS ARROW FFEA    ￪                               
HALFWIDTH WHITE CIRCLE  FFEE    ￮                               
HANGUL SYLLABLE BBWEOJ  BFFE    뿾                              
HANGUL SYLLABLE GGWELP  AFFE    꿾                              
HANGUL SYLLABLE KWEOGG  CFFE    쿾                              
MATHEMATICAL BOLD ITALIC PARTIAL DIFFERENTIAL   1D74F   𝝏       
MATHEMATICAL BOLD PARTIAL DIFFERENTIAL  1D6DB   𝛛               
MATHEMATICAL ITALIC PARTIAL DIFFERENTIAL        1D715   𝜕       
MATHEMATICAL SANS-SERIF BOLD ITALIC PARTIAL DIFFERENTIAL        1D7C3   𝟃 
MATHEMATICAL SANS-SERIF BOLD PARTIAL DIFFERENTIAL       1D789   𝞉 
PARTIAL DIFFERENTIAL    2202    ∂
____

The overlaps are for 7 char names and 20 code points.

If you were completing _separately_ against only char
names you would still have 7 candidates.  If against
only code points you would still have 20 candidates.
With both together you have 27.

If you typed `iffe' you'd get just 6 (char-name)
candidates.  If you typed `ffea' you'd get just the
char named `HALFWIDTH UPWARDS ARROW'.

[If you typed `[0-9a-f]ffe\|ffe[0-9a-f]' (with
regexp matching) you'd get only the 20 code-point
matches.]

Most char-name chars are not hex chars.  And most
hex-char combinations don't occur in char names.
And those that do occur in both typically don't
occur in many char names.
____

Of course it helps if you can match against multiple
regexps, progressively, as you see the results of
each match, to narrow the set incrementally.  Seeing
the 27 initial matches, typing another (separate)
pattern of, say, `bet' would immediately get you
only candidate `DIFFERENCE BETWEEN      224F    ≏'.
____

https://www.emacswiki.org/emacs/Icicles_-_Progressive_Completion