Show Font (show-font.el)

The commands show-font-tabulated (alias show-font-list) and show-font-select-preview can now generate a preview for fonts that are optimised to display the aforementioned languages. Each language provides its own user option to control the sample text it displays. The naming pattern show-font-LANGUAGE-sample.

Of those, I only know Greek and thus wrote the value of show-font-greek-sample, namely: "Πρωτεσίλαος ο φιλόσοφος του οποίου τα έργα βρίθουν αστειισμών". For the others I used translation software to get the equivalent of "Protesilaos does not read LANGUAGE". Please let me know if there are any mistakes in this regard. I was thinking of writing something a bit more funny, but was concerned the joke may not translate well.

While I have written functions that test if a given font can display a range of characters, this approach is computationally intensive if we need to check for many code points across multiple fonts.

The alternative is to maintain lists of known font families that are meant to work with the given language. Those generally support Latin as well, but the idea is to let them shine in the language they are meant to be used for.

For example, here is how we know that a font family is meant to display Arabic script:

(defconst show-font-arabic-families
  '("AlArabiya" "AlBattar" "AlHor" "AlManzomah" "AlYarmook"
    "Dimnah" "Hani" "Haramain" "Hor" "Kayrawan" "Khalid" "Mashq"
    "Nagham" "Noto Kufi Arabic" "Noto Naskh Arabic" "Noto Sans Arabic"
    "Rehan" "Sharjah" "Sindbad")
  "List of families that specialise in Arabic.
Also see `show-font-greek-families' for the rationale of grouping font
families in distinct variables.")

The list is not exhaustive and I am always eager to expand it. Just let me know.

I learnt about these font families through trial and error by (i) installing them on my Debian system and (ii) searching online for common samples of them. Do apt search -n fonts- to check the relevant packages.

As with the natural languages, there are some fonts that specialise in displaying symbols. For example, MathJax has a bunch of fonts for showing those fancy formulas in the processed output of LaTeX documents. Again, there is a defconst for each of those types of font listing the known families. The concomitant user options are:

• show-font-mathematics-sample
• show-font-music-sample
• show-font-symbols-sample

The show-font-hidden-families lists the fonts that are not known to cause problems. They do not render properly any of the supported samples and I am not sure even when they claim to support a certain set of characters (e.g. show-font--displays-latin-p returns non-nil). If you think there is a mistake here, please contact me.

While in the buffer produced by show-font-tabulated (alias show-font-list), type RET to get a complete preview of the font family of the current line. This is the same as invoking the command show-font-select-preview and then selecting the given family.

The command called by that key binding is show-font-tabulated-select-preview. A hint of it is also shown in the tabulated list header.

As above, type w in the tabulated view to copy the name of the font family to the kill-ring. The command is show-font-tabulated-copy-name and there is also a hint of it in the tabulated list header.

The show-font-list command was using a custom buffer that listed font families and their corresponding short preview. It did not have any other feature.

I made changes under the hood to rely on the built-in tabulated-list-mode which is a standard and gives us the option to sort by column. The show-font-list is thus an alias for the new command show-font-tabulated. Right now the sorting facility only applies to reversing the name-based order. In the future we may have more columns, such as if we describe a font as “Latin”, “Greek”, etc.

In the past, the font listing would include families that could not display the show-font-pangram or, indeed, any Latin character. Those would be rendered as empty boxes.

I have now introduced a simple heuristic to test that the given family supports Latin characters. If it does not, then (i) it is highlighted with a different colour, (ii) it shows “No preview” instead of the pangram, and (iii) it displays the information in the Emacs default font family. Some families do not play nice with this approach though, as they pass the test but still do not display any Latin characters. This happens with icon fonts.

The long-term goal is to support different scripts and show the appropriate text for each of them.

The new user option show-font-sentences-sample is a list of strings that can be used to exhibit common patterns and letter combinations. The default value is carefully designed to show if a font family is stylistically consistent, such as with how it draws i, l, t, or h, n, m, and so on. Plus, it teaches you some obscure words like “scholarch”, “antipode”, and “heteroclite”: use them with your Greek friends—and if they do not know those words, then they must buy you a café frappé!

• The face show-font-title-small is an obsolete alias for the more appropriately named show-font-title-in-listing.
• The prompt used by the command show-font-select-preview now correctly uses its own history and default value.
• The default value of the user option show-font-character-sample includes some more patterns to better test the adequacy of a font family. This sample is displayed in the buffer produced by the command show-font-select-preview.

The command show-font-tabulated will produce a listing of font families and their preview that uses the built-in tabulated interface. This interface is the same as the one used by M-x list-packages. Users can sort fonts by font family name (move point to the given column and type S or call M-x tabulated-list-sort).

When show-font-tabulated is called with a prefix argument (C-u by default), it prompts for a string or regular expression. It then shows only the font families matching the given input.

The command show-font-list which we already had in version 0.1.0 is like the show-font-tabulated, but uses a bespoke buffer where each font and its preview are shown one after the other. Now it also accepts an optional prefix argument to limit the list to only the matching fonts.

The preview buffers we use will now conform with the value of the new user option show-font-display-buffer-action-alist. This is a more advanced feature, due to how display-buffer works, so you may want to check the video I did recently about controlling where buffers are displayed: https://protesilaos.com/codelog/2024-02-08-emacs-window-rules-display-buffer-alist/.

The default value of show-font-display-buffer-action-alist will show the buffer at the bottom of the frame.