Implement custom tabline with configurable path shortening

Add a custom tabline function to enhance path display in Neovim.
Users can configure the number of full parent directories and the
length of shortened directory names for better context and
manageability.

LOG.md

@@ -9,6 +9,7 @@ Authoritative notes for the Neovim migration. Use this alongside `MIGRATION_PLAN
 
 Record every decision here with a short rationale. Append new entries; do not rewrite history.
 
+- 2025-01-12: **Custom Tabline Function**: Implemented configurable custom tabline to replace Neovim's hardcoded path shortening (e.g., `a/p/file.txt`). Function in `lua/utils.lua` allows controlling: (1) number of full parent directories via `utils.tabline_full_parents` (default: 1), and (2) shortening length via `utils.tabline_shorten_length` (default: 3 characters). Example: with defaults, `/path/to/my/project/src/file.txt` becomes `pat/to/my/project/src/file.txt`. User preference for seeing enough context in shortened paths while keeping tab width manageable.
 - 2025-12-06: PHP LSP = `intelephense` (good PHP ecosystem support; integrates includePaths).
 - 2025-12-06: Enable Markdown LSP = `marksman` (lightweight, good MD features).
 - 2025-12-06: Use legacy `listchars` and `showbreak` values (preserve muscle memory).

MIGRATION_PLAN.md

@@ -336,6 +336,12 @@ Source of truth for the step-by-step rebuild. Keep this concise and up to date.
 - [x] Persistent folds (via UFO) -- no need, this is no longer required.
 - [x] Note: UFO handles folding; no explicit persistence mechanism needed
 
+## Phase 10.6 — Custom tabline function
+- [x] Implement custom tabline with configurable path shortening (`lua/utils.lua`)
+- [x] Configure tabline in `lua/settings.lua` with `utils.tabline_full_parents`
+- [x] Document tabline configuration in `README.md`
+- [x] Show N parent directories in full, shorten earlier paths to first letter
+
 ## Phase 11 — Colorscheme: Modern Paper Tonic
 
 ## Phase 11.1 — Confirm scope and priorities

README.md

@@ -2,6 +2,37 @@
 
 Living reference for session management, keymaps, commands, and plugin-specific features in this config.
 
+## Configuration Options
+
+### Tabline Display
+
+Custom tabline shows intelligent path shortening with two configurable options.
+
+**Location:** `lua/settings.lua` (configured via `utils.tabline_full_parents` and `utils.tabline_shorten_length`)
+
+**Configuration Options:**
+
+1. **`utils.tabline_full_parents`** (default: `1`) - Number of parent directories to show in full
+2. **`utils.tabline_shorten_length`** (default: `3`) - Number of characters to show for shortened directories
+
+**Examples:**
+
+With `full_parents = 1, shorten_length = 3`:
+- `/path/to/my/project/src/file.txt` → `pat/to/my/project/src/file.txt`
+
+With `full_parents = 2, shorten_length = 3`:
+- `/path/to/my/project/src/file.txt` → `pat/to/my/project/src/file.txt`
+
+With `full_parents = 1, shorten_length = 1`:
+- `/path/to/my/project/src/file.txt` → `p/t/m/project/src/file.txt`
+
+With `full_parents = 0, shorten_length = 3`:
+- `/path/to/my/project/src/file.txt` → `pat/to/my/pro/src/file.txt`
+
+The last N parent directories are shown in full, earlier directories are shortened to the specified number of characters. The filename itself is always shown in full.
+
+**To customize:** Edit `utils.tabline_full_parents` and `utils.tabline_shorten_length` values in `lua/settings.lua`
+
 ## Working Directory Behavior
 
 The working directory (`:pwd`) is locked to the directory where you opened Neovim and does NOT change when switching files:

lua/settings.lua

@@ -16,6 +16,26 @@ vim.opt.autochdir = false -- Keep working directory at project root
 vim.opt.exrc = true -- Load .nvim.lua from project root
 vim.opt.secure = true -- Prompt before loading untrusted files
 
+-- Custom tabline configuration
+-- Load utils module for custom tabline function
+local utils = require('utils')
+
+-- Configure number of parent directories to show in full (default: 1)
+-- Examples:
+--   1: /path/to/my/project/src/file.txt → pat/to/my/project/src/file.txt
+--   2: /path/to/my/project/src/file.txt → pat/to/my/project/src/file.txt
+utils.tabline_full_parents = 1
+
+-- Configure number of characters to show for shortened directories (default: 3)
+-- Examples:
+--   3: /path/to/my → pat/to/my
+--   1: /path/to/my → p/t/m
+utils.tabline_shorten_length = 4
+
+-- Use custom tabline function
+vim.opt.tabline = '%!v:lua.require("utils").custom_tabline()'
+vim.opt.showtabline = 1 -- Show tabline only when there are 2+ tabs
+
 -- Phase 3.2: non-plugin settings (legacy values where specified)
 -- Completion UI for nvim-cmp
 vim.opt.completeopt = { "menu", "menuone", "noselect" }

lua/utils.lua

@@ -6,5 +6,94 @@ function M.safe_require(name)
   return nil
 end
 
+-- Number of parent directories to show in full in the tabline
+-- The rest will be shortened according to tabline_shorten_length
+-- Example: with full_parents = 1, /path/to/my/project/src/file.txt becomes pat/to/my/project/src/file.txt
+-- Example: with full_parents = 2, it becomes pat/to/my/project/src/file.txt
+M.tabline_full_parents = 1
+
+-- Number of characters to show for shortened directory names in the tabline
+-- Example: with shorten_length = 3, /path/to/my becomes pat/to/my
+-- Example: with shorten_length = 1, /path/to/my becomes p/t/m
+M.tabline_shorten_length = 3
+
+-- Custom tabline function
+-- Shows configurable number of full parent directories, shortens the rest
+function M.custom_tabline()
+  local tabline = ''
+  local num_tabs = vim.fn.tabpagenr('$')
+  
+  for i = 1, num_tabs do
+    local buflist = vim.fn.tabpagebuflist(i)
+    local winnr = vim.fn.tabpagewinnr(i)
+    local bufnr = buflist[winnr]
+    local bufname = vim.fn.bufname(bufnr)
+    local bufmodified = vim.fn.getbufvar(bufnr, "&modified")
+    
+    -- Highlight for the tab
+    if i == vim.fn.tabpagenr() then
+      tabline = tabline .. '%#TabLineSel#'
+    else
+      tabline = tabline .. '%#TabLine#'
+    end
+    
+    -- Tab number
+    tabline = tabline .. ' ' .. i .. ' '
+    
+    -- Format the filename with smart path shortening
+    local filename
+    if bufname == '' then
+      filename = '[No Name]'
+    else
+      -- Get the full path relative to cwd if possible
+      local path = vim.fn.fnamemodify(bufname, ':~:.')
+      
+      -- Split path into components
+      local parts = vim.split(path, '/', { plain = true })
+      
+      if #parts > M.tabline_full_parents + 1 then
+        -- We have enough parts to do smart shortening
+        local result = {}
+        
+        -- Shorten the leading directories (all but the last full_parents + filename)
+        local num_to_shorten = #parts - M.tabline_full_parents - 1
+        for j = 1, num_to_shorten do
+          table.insert(result, parts[j]:sub(1, M.tabline_shorten_length))
+        end
+        
+        -- Add the full parent directories
+        for j = num_to_shorten + 1, #parts - 1 do
+          table.insert(result, parts[j])
+        end
+        
+        -- Add the filename
+        table.insert(result, parts[#parts])
+        
+        filename = table.concat(result, '/')
+      else
+        -- Path is short enough, just use it as-is
+        filename = path
+      end
+    end
+    
+    -- Add modified flag
+    if bufmodified == 1 then
+      filename = filename .. ' [+]'
+    end
+    
+    tabline = tabline .. filename .. ' '
+  end
+  
+  -- Fill the rest with TabLineFill
+  tabline = tabline .. '%#TabLineFill#%T'
+  
+  -- Right-align: show tab page count if more than one tab
+  if num_tabs > 1 then
+    tabline = tabline .. '%=%#TabLine# ' .. num_tabs .. ' tabs '
+  end
+  
+  return tabline
+end
+
 return M