feat(colors): optionally get the cursor color from the hl group at th…

…e cursor

lua/smear_cursor/color.lua

@@ -3,30 +3,9 @@ local logging = require("smear_cursor.logging")
 local round = require("smear_cursor.math").round
 local M = {}
 
--- TODO: does not work
-M.get_hl_group = function(row, col)
-	-- Retrieve the current buffer
-	local buffer_id = vim.api.nvim_get_current_buf()
-
-	local extmarks = vim.api.nvim_buf_get_extmarks(buffer_id, -1, { row, col }, { row, col + 1 }, {
-		details = true,
-		overlap = true,
-	})
-	logging.debug(vim.inspect(extmarks))
-
-	if #extmarks > 0 then
-		local extmark = extmarks[1]
-		if extmark[4] and extmark[4].hl_group then
-			return extmark[4].hl_group
-		end
-	end
-
-	return "Normal"
-end
-
 -- Get a color from a highlight group
 local function get_hl_color(group, attr)
-	local hl = vim.api.nvim_get_hl_by_name(group, true)
+	local hl = vim.api.nvim_get_hl(0, { name = group, link = false })
 	if hl[attr] then
 		return string.format("#%06x", hl[attr])
 	end
@@ -36,6 +15,7 @@ end
 local cursor_color = nil
 local normal_bg = nil
 local transparent_bg_fallback_color = "#303030"
+local cache = {} ---@type table<string, boolean>
 
 local function hex_to_rgb(hex)
 	hex = hex:gsub("#", "")
@@ -58,72 +38,95 @@ local function interpolate_colors(hex1, hex2, t)
 	return rgb_to_hex(r, g, b)
 end
 
-M.set_hl_groups = function()
+function M.clear()
+	cache = {}
+end
+
+---@param opts? {level?: number, inverted?: boolean}
+function M.get_hl_group(opts)
+	opts = opts or {}
+	local _cursor_color ---@type string?
+
+	local hl_group = ("SmearCursorNormal%s"):format(opts.inverted and "Inverted" or "", opts.level or 0)
+
+	-- Get the cursor color from the treesitter highlight group
+	-- at the cursor.
+	if cursor_color == "treesitter" and vim.b.ts_highlight then
+		local cursor = vim.api.nvim_win_get_cursor(0)
+		local ts_hl_group ---@type string?
+		for _, capture in pairs(vim.treesitter.get_captures_at_pos(0, cursor[1] - 1, cursor[2])) do
+			ts_hl_group = "@" .. capture.capture .. "." .. capture.lang
+		end
+		local ts_color = ts_hl_group and get_hl_color(ts_hl_group, "fg")
+		if ts_color then
+			_cursor_color = ts_color
+			hl_group = hl_group .. "_" .. ts_color:sub(2)
+		end
+	end
+
+	if cache[hl_group] then
+		return hl_group
+	end
+
+	local _normal_bg = normal_bg or get_hl_color("Normal", "bg") or "none"
+
 	-- Retrieve the cursor color and the normal background color if not set by the user
-	local _cursor_color = cursor_color
-		or get_hl_color("Cursor", "background")
-		or get_hl_color("Normal", "foreground")
-		or "#d0d0d0"
-	local _normal_bg = normal_bg or get_hl_color("Normal", "background") or "none"
+	_cursor_color = _cursor_color or get_hl_color("Cursor", "bg") or get_hl_color("Normal", "fg") or "#d0d0d0"
 
 	-- Blending breaks with transparent backgrounds
 	local blending = config.legacy_computing_symbols_support and _normal_bg ~= "none"
 
-	vim.api.nvim_set_hl(0, M.hl_group, {
-		fg = _cursor_color,
-		bg = "none",
-		blend = blending and 100 or 0,
-	})
-	vim.api.nvim_set_hl(
-		0,
-		M.hl_group_inverted,
-		-- Blending does not work as we'd like with reversed colors
-		{ fg = _normal_bg == "none" and transparent_bg_fallback_color or _normal_bg, bg = _cursor_color, blend = 0 }
-	)
-
-	M.hl_groups = {}
-	M.hl_groups_inverted = {}
-
-	for i = 1, config.color_levels do
-		local opacity = (i / config.color_levels) ^ (1 / config.gamma)
-		local blended_cursor_color = interpolate_colors(
+	if opts.level then
+		local opacity = (opts.level / config.color_levels) ^ (1 / config.gamma)
+		_cursor_color = interpolate_colors(
 			_normal_bg == "none" and transparent_bg_fallback_color or _normal_bg,
 			_cursor_color,
 			opacity
 		)
-		local blended_hl_group = M.hl_group .. i
-		local blended_hl_group_inverted = M.hl_group_inverted .. i
-		M.hl_groups[i] = blended_hl_group
-		M.hl_groups_inverted[i] = blended_hl_group_inverted
-
-		vim.api.nvim_set_hl(0, blended_hl_group, {
-			fg = blended_cursor_color,
-			bg = _normal_bg,
-			blend = blending and 100 or 0,
-		})
-		vim.api.nvim_set_hl(0, blended_hl_group_inverted, {
-			fg = _normal_bg == "none" and transparent_bg_fallback_color or _normal_bg,
-			bg = blended_cursor_color,
-			blend = 0,
-		})
 	end
+
+	---@type vim.api.keyset.highlight
+	local hl = opts.inverted
+			and {
+				fg = _normal_bg == "none" and transparent_bg_fallback_color or _normal_bg,
+				bg = _cursor_color,
+				blend = 0,
+			}
+		or {
+			fg = _cursor_color,
+			bg = "none", -- _normal_bg,
+			blend = blending and 100 or 0,
+		}
+
+	vim.api.nvim_set_hl(0, hl_group, hl)
+	cache[hl_group] = true
+	return hl_group
 end
 
 -- Define new highlight groups using the retrieved colors
-M.hl_group = "SmearCursorNormal"
-M.hl_group_inverted = "SmearCursorNormalInverted"
-M.hl_groups = {}
-M.hl_groups_inverted = {}
-M.set_hl_groups()
+M.hl_groups = setmetatable({}, {
+	__index = function(_, key)
+		return M.get_hl_group({ level = key })
+	end,
+})
+M.hl_groups_inverted = setmetatable({}, {
+	__index = function(_, key)
+		return M.get_hl_group({ level = key, inverted = true })
+	end,
+})
 
 local metatable = {
-	__index = function(table, key)
+	__index = function(_, key)
 		if key == "cursor_color" then
 			return cursor_color
 		elseif key == "normal_bg" then
 			return normal_bg
 		elseif key == "transparent_bg_fallback_color" then
 			return transparent_bg_fallback_color
+		elseif key == "hl_group" then
+			return M.get_hl_group()
+		elseif key == "hl_group_inverted" then
+			return M.get_hl_group({ inverted = true })
 		else
 			return nil
 		end
@@ -132,13 +135,13 @@ local metatable = {
 	__newindex = function(table, key, value)
 		if key == "cursor_color" then
 			cursor_color = value
-			M.set_hl_groups()
+			M.clear()
 		elseif key == "normal_bg" then
 			normal_bg = value
-			M.set_hl_groups()
+			M.clear()
 		elseif key == "transparent_bg_fallback_color" then
 			transparent_bg_fallback_color = value
-			M.set_hl_groups()
+			M.clear()
 		else
 			rawset(table, key, value)
 		end

lua/smear_cursor/events.lua

@@ -38,7 +38,7 @@ M.listen = function()
 			autocmd CursorMoved * lua require("smear_cursor.events").move_cursor()
 			autocmd CursorMovedI,WinScrolled * lua require("smear_cursor.events").jump_cursor()
 			autocmd BufLeave * lua require("smear_cursor.events").flag_switching_buffer()
-			autocmd ColorScheme * lua require("smear_cursor.color").set_hl_groups()
+			autocmd ColorScheme * lua require("smear_cursor.color").clear()
 		augroup END
 	]],
 		false

lua/smear_cursor/init.lua

@@ -38,7 +38,7 @@ local metatable = {
 			color[key] = value
 		elseif key == "legacy_computing_symbols_support" then
 			config.legacy_computing_symbols_support = value
-			color.set_hl_groups()
+			color.clear()
 		elseif config[key] ~= nil then
 			config[key] = value
 		else