bug#74362: 31.0.50; Add completions for font names

bug#74362: 31.0.50; Add completions for font names

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Package: Emacs
Version: 31.0.50


In the UI of `customize-face`, the font family name is the main one that
provides no help to fill it.
The simple patch below provides completion (I had to put the completion
function in `cus-edit.el` because of a circularity between
`cus-face.el` and `minibuffer.el` so we can't call
`completion-table-dynamic` while loading `cus-face.el`).

Comments/objections?


        Stefan


diff --git a/lisp/cus-edit.el b/lisp/cus-edit.el
index 8eba4270bcb..763dfc31fb8 100644
--- a/lisp/cus-edit.el
+++ b/lisp/cus-edit.el
@@ -3425,6 +3425,12 @@ custom-visibility
 
 ;;; The `custom-face-edit' Widget.
 
+(defalias 'custom-face--font-completion 
+  (completion-table-dynamic
+   (lambda (_string)
+     (nconc (mapcar #'car face-font-family-alternatives)
+            (font-family-list)))))
+
 (define-widget 'custom-face-edit 'checklist
   "Widget for editing face attributes.
 The following properties have special meanings for this widget:
diff --git a/lisp/cus-face.el b/lisp/cus-face.el
index d0a1a66e29f..9a0ab4b47c7 100644
--- a/lisp/cus-face.el
+++ b/lisp/cus-face.el
@@ -48,6 +48,7 @@ custom-declare-face
 (defconst custom-face-attributes
   `((:family
      (string :tag "Font Family"
+	     :completions custom-face--font-completion
 	     :help-echo "Font family or fontset alias name."))
 
     (:foundry

bug#74362: 31.0.50; Add completions for font names

[Robert Pluim]

>>>>> On Thu, 14 Nov 2024 17:48:54 -0500, Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org> said:

    Stefan> Package: Emacs
    Stefan> Version: 31.0.50


    Stefan> In the UI of `customize-face`, the font family name is the main one that
    Stefan> provides no help to fill it.
    Stefan> The simple patch below provides completion (I had to put the completion
    Stefan> function in `cus-edit.el` because of a circularity between
    Stefan> `cus-face.el` and `minibuffer.el` so we can't call
    Stefan> `completion-table-dynamic` while loading `cus-face.el`).

    Stefan> Comments/objections?

You have trailing whitespace. Also it would be better if this was
wrapped in `completion-table-case-fold', I think (everyone disagrees
on how to write "mono").

Robert
-- 

bug#74362: 31.0.50; Add completions for font names

[Eli Zaretskii]

> Cc: monnier@iro.umontreal.ca
> Date: Thu, 14 Nov 2024 17:48:54 -0500
> From:  Stefan Monnier via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> In the UI of `customize-face`, the font family name is the main one that
> provides no help to fill it.
> The simple patch below provides completion (I had to put the completion
> function in `cus-edit.el` because of a circularity between
> `cus-face.el` and `minibuffer.el` so we can't call
> `completion-table-dynamic` while loading `cus-face.el`).
> 
> Comments/objections?

I suggest to try this on a system that has a lot of fonts installed,
to make sure this doesn't slow down customize-face too much.  In
bug#74337 a user reported that font-family-list returned a list of no
fewer than 10775(!) families.  I wonder what will that do to this
command.

Also, the doc string of customize-face should be amended to say that
it offers completion on fonts.

Btw, how does one invoke completion on the face attributes which are
supposed to provide one, such as weight or colors?  M-C-i doesn't seem
to do it for me, or what am I missing?

bug#74362: 31.0.50; Add completions for font names

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

> You have trailing whitespace.

Thanks.  🙂

> Also it would be better if this was wrapped in
> `completion-table-case-fold', I think (everyone disagrees on how to
> write "mono").

So you're saying font family names are case-insensitive?
I was wondering about that and couldn't find it documented anywhere.


        Stefan