Use simpler symbols if Nerd Font isn't available

[heathhenley]

From discussion here: #8 (comment)
eg:

it's probably a good idea to check for the supported font and use some alternative simpler symbols

If Hack Nerd Font Mono isn't installed, the icons for text files, folders, binary files, etc render as something like �. Seems like this would involve checking if the font is available, and if not selecting more widely supported alternatives for the icons.

Maybe there could also be a note in "About" or something to hint that you should install nerd font?

[chshersh]

@heathhenley Thanks for creating an issue! I can see several subtasks here:

• Detect if the Nerd Font Mono installed (I have no idea how to do it yet, need to research)
• Find alternative simple icons
• Somehow parametrise the view to dynamically select icons based on the setting
• Display a warning (this probably deserves a separate discussion on, how to display it)

Currently, all icons are written here:

github-tui/lib/tui/widget.ml

Lines 57 to 60 in 71fa359

	let pwd_char = "\u{e5fd}"
	let dir_char = "\u{f4d4}"
	let empty_dir_char = "\u{f413}"
	let file_char = "\u{f4a5}"

[heathhenley]

Looked into this a little bit - one way to check if they're installed may be to enumerate the common places they are stored - on linux, there is fc-list that already does this:

root@Heaths-Laptop:~/github-tui# fc-list | grep -i "Hack Nerd Font Mono"
/root/.fonts/HackNerdFontMono-Regular.ttf: Hack Nerd Font Mono:style=Regular

If we don't want to use fc-list, it looks like we can check a few directories and have a good chance of being correct (/usr/share/fonts, ~/.fonts/, ~/.local/share/fonts, etc)

On Windows, there's a couple registry keys that list the system wide font or fonts installed for a single user (They're under HKCU|HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts) - eg:

PS C:\Users\hhenl> Get-ItemProperty 'HKCU:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts'

Hack Nerd Font Regular (TrueType)      : C:\Users\hhenl\AppData\Local\Microsoft\Windows\Fonts\HackNerdFont-Regular.ttf
Hack Nerd Font Mono Regular (TrueType) : C:\Users\hhenl\AppData\Local\Microsoft\Windows\Fonts\HackNerdFontMono-Regular.ttf
PSPath                                 : Microsoft.PowerShell.Core\Registry::HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts

But really there are also only a couple places that they are likely to be: C:\Windows\Fonts or in C:\Users\<USER>\AppData\Local\Microsoft\Windows\Fonts

So as a first pass at just detecting if the font is there - we could:

• On Windows enumerate the common directories to check for it - so we don't have to pull any deps to read registry keys, although that would probably be more robust
• Maybe on Linux still use an fc-list sys call because it will be more robust and very straight forward to do

I didn't look into mac though, it might have an fc-list too but I can't test that one.

[chshersh]

Wow, @heathhenley, this is an amazing investigation! I checked the fc-list solution and it works even in WSL 🚀

I don't think we need to care about Windows support for now (saying this as someone who uses Windows). GitHub TUI uses UNIX API, so making it work on Windows will be quite an effort.

I also propose adding a CLI flag to use plain symbols, so the user can always override our logic if it's not precise enough.

But the first step here would be to centralise all characters in one place, so we have control over them.

As a first step, I'm thinking about creating a module Pretty.Icon and putting all the characters there. Quick search reveals we have this now:

❯  rg "\"\\\u"
lib/tui/widget/pr.ml
3:let closed_char = "\u{ebda}"
4:let open_char = "\u{ea64}"
5:let merged_char = "\u{e725}"

lib/tui/widget/generic.ml
25:let arrow_left_char = "\u{f0a8}"

lib/tui/widget/code.ml
10:let pwd_char = "\u{e5fd}"
11:let dir_char = "\u{f4d4}"
12:let empty_dir_char = "\u{f413}"
13:let file_char = "\u{f4a5}"
14:let bin_char = "\u{eae8}"

lib/tui/widget/common.ml
7:          "\u{26A0} GITHUB_TOKEN not found. Make sure it's configured in your \
15:        str (Format.sprintf "\u{26A0} [%d] %s" code msg);
21:        str (Format.sprintf "\u{26A0} GitHub API returned error code %d: " code);

lib/tui/render/render.ml
9:let issue_char = "\u{f41b}"

[heathhenley]

Any thoughts on where the function to check if the font is installed should live?