feat: add transparent bg option

fix: add comment explaining lazyvim var

README.md

@@ -107,7 +107,7 @@ require("ashen").setup({
 vim.cmd("colorscheme ashen")
 ```
 
-The following default settings are provided. Any settings not self-explanatory will be expanded on below. Any provided settings will be merged with the defaults.
+The following default settings are provided. User provided settings will be merged with the defaults. For settings that are not self-explanatory, please see below.
 
 ```Lua
 {
@@ -124,6 +124,8 @@ The following default settings are provided. Any settings not self-explanatory w
     ---@type HighlightMap
     merge_override = {},
   },
+  -- use transparent background
+  transparent = false,
   -- force clear other highlights
   -- even if no other theme is set
   -- (useful for debugging)

lua/ashen/init.lua

@@ -1,5 +1,8 @@
 local M = {}
 
+-- highlight on yank needs to be set
+-- differently using lazyvim so we
+-- have to track whether the user is running it
 M.lazyvim = false
 
 -- default settings
@@ -17,6 +20,8 @@ M.opts = {
     ---@type HighlightMap
     merge_override = {},
   },
+  -- use transparent background
+  transparent = false,
   -- force clear other highlights
   force_hi_clear = false,
   -- enable termguicolors on load

lua/ashen/theme.lua

@@ -217,11 +217,23 @@ M.map = {
   String = { c.red_glowing, nil },
 }
 
+---@type string[]
+M.transparent_bg = {
+  "Normal",
+  "SignColumn",
+  "LineNr",
+}
+
 ---override HL groups
 ---@param opts Options
 M.setup = function(opts)
   -- TODO: Let users provide palette color names instead of Hex codes
   -- and check for it automatically
+  if opts.transparent then
+    for _, name in ipairs(M.transparent_bg) do
+      M.map[name] = util.remove_bg(M.map[name])
+    end
+  end
   for k, v in pairs(opts.hl.merge_override or {}) do
     M.map[k] = vim.tbl_deep_extend("force", M.map[k], v)
   end

lua/ashen/util.lua

@@ -45,6 +45,11 @@ M.hl = function(name, spec)
   if not M.is_norm(spec) then
     spec = M.normalize_hl(spec)
   end
+  -- check if transparency is enabled
+  -- this is too costly to do on each hl, though
+  if require("ashen.theme").transparent_bg[name] then
+    spec.bg = nil
+  end
   -- -- Debugging output to verify the structure
   -- for k, v in pairs(spec) do
   --   if type(k) ~= "string" then
@@ -55,6 +60,28 @@ M.hl = function(name, spec)
   return true
 end
 
+---@param spec HighlightNormalized
+---@return HighlightSpec
+local function denormalize(spec)
+  local fg = spec.fg
+  spec.fg = nil
+  local bg = spec.bg
+  spec.bg = nil
+  return { fg, bg, spec }
+end
+
+---@param spec HighlightSpec|HighlightNormalized
+M.remove_bg = function(spec)
+  if not M.is_norm(spec) then
+    local norm = M.normalize_hl(spec)
+    norm.bg = nil
+    return denormalize(norm)
+  else
+    spec.bg = nil
+    return spec
+  end
+end
+
 function M.link_lang(table, lang)
   for hl, input in pairs(table) do
     local l = input .. "." .. lang