refactor(win): use vim.str_utfindex/str_byteindex for UTF-8 operations

Author: ibhagwan

lua/fzf-lua/win.lua

@@ -97,14 +97,9 @@ function PathShortener._apply_line(buf, row, shorten_len)
     local component = path_portion:sub(component_start, sep_pos - 1)
     local component_len = #component
 
-    -- Count UTF-8 characters using path.utf8_char_len
-    local component_charlen = 0
-    local byte_i = 1
-    while byte_i <= component_len do
-      local c_len = path.utf8_char_len(component, byte_i) or 1
-      component_charlen = component_charlen + 1
-      byte_i = byte_i + c_len
-    end
+    -- Count UTF-8 characters using vim.str_utfindex
+    local _, component_charlen = vim.str_utfindex(component, "utf-32")
+    component_charlen = component_charlen or component_len -- fallback to byte length
 
     -- Only conceal if the component has more characters than shorten_len
     if component_charlen > shorten_len then
@@ -118,16 +113,9 @@ function PathShortener._apply_line(buf, row, shorten_len)
       -- Bounds check to prevent errors
       keep_chars = math.min(keep_chars, component_charlen)
 
-      -- Convert character count to byte offset using path.utf8_char_len
-      local keep_bytes = 0
-      local char_count = 0
-      byte_i = 1
-      while byte_i <= component_len and char_count < keep_chars do
-        local c_len = path.utf8_char_len(component, byte_i) or 1
-        keep_bytes = keep_bytes + c_len
-        char_count = char_count + 1
-        byte_i = byte_i + c_len
-      end
+      -- Convert character count to byte offset using vim.str_byteindex
+      local keep_bytes = vim.str_byteindex(component, "utf-32", keep_chars, false)
+      keep_bytes = keep_bytes or keep_chars -- fallback to character count (ASCII approximation)
 
       -- Calculate 0-indexed byte positions in the full line for extmark
       -- path_start is 1-indexed, component_start is 1-indexed within path_portion