refactor: generate icons from their glyph names

.gitignore

@@ -1,3 +1,4 @@
 .lua
 .luarocks
+/nerd-fonts/
 /vim-colortemplate/

Makefile

@@ -1,8 +1,9 @@
+NERD_FONTS_VERSION = 3.1.1
 VIM_COLORTEMPLATE_VERSION = 2.2.3
 
 all: colors style-check lint
 
-colors: vim-colortemplate
+colors: nerd-fonts vim-colortemplate
 	nvim \
 		--clean \
 		--headless \
@@ -18,6 +19,9 @@ colors-check: colors
 vim-colortemplate:
 	git clone --depth 1 -b v$(VIM_COLORTEMPLATE_VERSION) https://github.com/lifepillar/vim-colortemplate.git vim-colortemplate
 
+nerd-fonts:
+	git clone --depth 1 --filter blob:none --sparse -b v$(NERD_FONTS_VERSION) https://github.com/ryanoasis/nerd-fonts.git nerd-fonts
+
 style-check:
 	stylua . --check
 
@@ -28,6 +32,6 @@ lint:
 	luacheck lua
 
 clean:
-	rm -rf vim-colortemplate
+	rm -rf nerd-fonts vim-colortemplate
 
 .PHONY: all colors style-check style-fix lint

lua/nvim-web-devicons/_gen/color.lua

@@ -0,0 +1,44 @@
+local M = {}
+
+---@param rrggbb string
+---@return string
+function M.darken(rrggbb)
+  local light78 = 255 * 7 / 8
+  local light68 = 255 * 6 / 8
+  local light58 = 255 * 5 / 8
+  local light12 = 255 / 2
+  local light13 = 255 / 3
+
+  local hex = bit.tohex ---@type fun(n: number): string
+
+  local r, g, b = rrggbb:match "%#(%x%x)(%x%x)(%x%x)"
+  r, g, b = tonumber("0x" .. r), tonumber("0x" .. g), tonumber("0x" .. b)
+  -- luminance formula: see https://stackoverflow.com/a/596243
+  local lum = 0.299 * r + 0.587 * g + 0.114 * b
+  if lum < light13 then -------------------- darkest tertile
+    return rrggbb
+  elseif lum < light12 then ---------------- second darkest quartile
+    r = hex(r / 4 * 3):sub(-2)
+    g = hex(g / 4 * 3):sub(-2)
+    b = hex(b / 4 * 3):sub(-2)
+  elseif lum < light58 then ---------------- lightest octiles: first
+    r = hex(r / 3 * 2):sub(-2)
+    g = hex(g / 3 * 2):sub(-2)
+    b = hex(b / 3 * 2):sub(-2)
+  elseif lum < light68 then ---------------- lightest octiles: second
+    r = hex(r / 2):sub(-2)
+    g = hex(g / 2):sub(-2)
+    b = hex(b / 2):sub(-2)
+  elseif lum < light78 then ---------------- lightest octiles: third
+    r = hex(r / 3):sub(-2)
+    g = hex(g / 3):sub(-2)
+    b = hex(b / 3):sub(-2)
+  else ------------------------------------- lightest octile
+    r = hex(r / 5):sub(-2)
+    g = hex(g / 5):sub(-2)
+    b = hex(b / 5):sub(-2)
+  end
+  return string.format("#%s%s%s", r, g, b)
+end
+
+return M