commit f2c0a5f8c6446ca58c1b306a7e04c8e58d366c6c
Author: rnhmjoj <rnhmjoj@inventati.org>
Date:   Tue Sep 6 17:09:28 2022 +0200

    Initial commit

diff --git a/LICENSE b/LICENSE
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+MIT License
+
+Copyright (c) 2020-2022 TJ DeVries, Michele Guerini Rocco
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
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+# Frameline
+
+### Very minimal framework to write a status/tabline
+
+Frameline is a Lua library for writing your own statusline (and also a tabline)
+for Neovim. This is not a ready-made statusline plugin, it's essential just the
+*frame*, you have to built the rest by yourself.
+
+Frameline is around 200 lines of Lua with no external dependencies.
+
+## Examples
+
+1. A statusline with the usual components: mode, git branch, filename,
+   encoding, etc.
+
+    ```lua
+    local frameline = require 'frameline'
+    local utils = frameline.utils
+
+    -- Some components
+    function mode(win, buf)
+      if not win.is_active then return end
+
+      local k = vim.api.nvim_get_mode().mode
+      local modes = {
+        n={'Normal', 'Normal'},
+        i={'Insert', 'Insert'},
+        R={'Replas', 'Insert'},
+        v={'Visual', 'Visual'},
+        V={'V⋅Line', 'VLine'},
+        t={'Termin', 'Term'},
+        ['']={'V⋅Bloc', 'VBloc'}
+      }
+      return utils.highlight('Mode'..modes[k][2], ' '..modes[k][1]..' ')
+    end
+
+    function branch(_, buf)
+      local head = vim.fn.FugitiveHead()
+      if buf.modifiable and head ~= "" then return '⚑ '..head end
+    end
+
+    function filename(_, buf)
+      local delta = ""
+      if buf.modified then delta = 'Δ' end
+      if not buf.modifiable then delta = '∇' end
+      local fname = buf.name ~= "" and utils.filename or 'new-file'
+      return delta..fname
+    end
+
+    function readonly(_, buf)
+      if buf.modifiable and buf.readonly then return '∅' end
+    end
+
+    function encoding(_, buf)
+      return buf.fileencoding ~= "" and buf.fileencoding or nil
+    end
+
+    function filetype(_, buf)
+      return buf.filetype ~= "" and buf.filetype or 'no ft'
+    end
+
+    -- Statusline
+    frameline.setup_statusline(function()
+      local segments = {}
+
+      -- Left section
+      table.insert(segments, utils.subsection{items={mode}})
+      table.insert(segments, utils.subsection{
+        separator=' → ',
+        items={branch, filename, readonly},
+      })
+      table.insert(segments, utils.split)
+
+      -- Right section
+      table.insert(segments, utils.subsection{
+        user=2,
+        separator=':', stop=' ',
+        items={utils.line_number, utils.column_number},
+      })
+      table.insert(segments, utils.subsection{
+        user=1,
+        separator=' ∘ ',
+        items={utils.percent, encoding, filetype}
+      })
+
+      return segments
+    end)
+    ```
+
+2. A tabline that shows the current tab, open tabs and date.
+
+    ```lua
+      -- Tabline
+      frameline.setup_tabline(function()
+        local segments = {}
+        local api = vim.api
+        local color = '%#StatusLine#'
+
+        -- Tabs
+        local current = api.nvim_get_current_tabpage()
+        local label = ' %d %s '
+        for i, tab in pairs(api.nvim_list_tabpages()) do
+          -- tab -> active win -> active buf -> name
+          local active_buf = api.nvim_win_get_buf(api.nvim_tabpage_get_win(tab))
+          local name = api.nvim_buf_get_name(active_buf)
+          name = vim.fn.fnamemodify(name, ':t')  -- filename only
+
+          local group = tab == current and 'TablineTabCur' or 'TablineTab'
+          table.insert(segments, utils.highlight(group, label:format(i, name)))
+        end
+
+        table.insert(segments, color)
+        table.insert(segments, utils.split)
+
+        -- Current date
+        table.insert(segments, vim.fn.strftime("%a %H:%M"))
+
+        return table.concat(segments)
+      end)
+    ```
+
+## License
+
+Frameline is licensed under the MIT license.
+See the accompanying file LICENSE or https://mit-license.org/.
diff --git a/default.nix b/default.nix
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+{ lib, runCommand }:
+
+runCommand "nvim-frameline"
+  { pname = "nvim-frameline";
+    version = "0.1.0";
+
+    meta = with lib; {
+      description = "Very minimal framework to write a status/tabline";
+      homepage = "https://maxwell.ydns.eu/git/rnhmjoj/nvim-frameline";
+      license = licenses.mit;
+      maintainers = [ maintainers.rnhmjoj ];
+      platforms = platforms.all;
+    };
+  }
+  ''
+    install -m644 -D ${./frameline.lua} "$out/lua/frameline/init.lua"
+  ''
diff --git a/frameline.lua b/frameline.lua
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+-- Very minimal framework to write a status/tabline
+-- Based on a (literally) stripped-down express_line.
+-- License: MIT
+-- Copyright © 2022 TJ DeVries, Michele Guerini Rocco
+
+
+local fl = {}
+
+-- Misc utilities
+fl.utils = {
+  -- Built-in segments
+  line_number = '%l',
+  column_number = '%c',
+  percent = "%p%%",
+  filename = '%t',
+  split = '%=',
+
+  -- Highlights a string
+  highlight = function(group, content)
+    return ('%%#%s#'):format(group) .. content .. '%*'
+  end,
+
+  -- Creates a subsection {highlight, items, separator, stop}
+  subsection = function(cfg)
+    local segments = {}
+
+    if cfg.user ~= nil then
+      table.insert(segments, ('%%%s*'):format(cfg.user))
+    end
+    if cfg.highlight ~= nil then
+      table.insert(segments, ('%%#%s#'):format(cfg.highlight))
+    end
+
+    table.insert(segments, function(win, buf)
+      local res, last_active = "", false
+
+      for i, item in pairs(cfg.items) do
+        local part = type(item) == 'string' and item or item(win, buf)
+        if part and last_active then
+          res = res .. (cfg.separator or ' ')
+        end
+        if part then
+          res = res .. part
+          last_active = true
+        end
+      end
+      return res
+    end)
+    table.insert(segments, cfg.stop or ' ')
+
+    if highlight ~= nil or user ~= nil then
+      table.insert(segments, '%*')
+    end
+
+    return segments
+  end
+}
+
+-- Neovim Buffer class
+local Buffer = {}
+local buf_props = {
+  name      = function(buf) return vim.api.nvim_buf_get_name(buf.bufnr) end,
+  is_active = function(buf) return buf.bufnr == vim.api.nvim_get_current_buf() end,
+}
+function Buffer:new(bufnr)
+  if bufnr == 0 then
+    bufnr = vim.api.nvim_buf_get_number(0)
+  end
+
+  return setmetatable({ bufnr = bufnr, }, { __index=function(t, k)
+    if Buffer[k] ~= nil then
+      t[k] = Buffer[k]
+    elseif buf_props[k] ~= nil then
+      t[k] = buf_props[k](t)
+    else
+      t[k] = vim.api.nvim_buf_get_option(t.bufnr, k)
+    end
+    return t[k]
+  end
+  })
+end
+
+-- Neovim Window class
+local Window = {}
+local win_props = {
+  width     = function(win) return vim.api.nvim_win_get_width(win.winid) end,
+  height    = function(win) return vim.api.nvim_win_get_height(win.winid) end,
+  is_active = function(win) return win.winid == vim.api.nvim_get_current_win() end
+}
+function Window:new(winid)
+  return setmetatable({winid=winid}, { __index=function(t, k)
+    local result
+    if Window[k] ~= nil then
+      result = Window[k]
+    elseif win_props[k] ~= nil then
+      result = win_props[k](t)
+    end
+    return result
+  end
+  })
+end
+
+-- Evaluates the statusline segments
+local processor = function(items, window, buffer)
+  local winid = window.winid
+
+  return function()
+    if not vim.api.nvim_win_is_valid(winid) then return end
+
+    buffer = Buffer:new(buffer.bufnr)
+    local waiting = {}
+    local statusline = {}
+    local effects = {}
+
+    for k, v in ipairs(items) do
+      local ok, result, effect
+      if type(v) == 'string' then
+        ok, result = true, v
+      elseif type(v) == 'function' then
+        ok, result, effect = pcall(v, window, buffer)
+      else
+        ok = false
+      end
+
+      if not ok then
+        statusline[k] = ''
+      else
+        if type(result) == 'thread' then
+          table.insert(waiting, {index=k, thread=result, effect=effect})
+        else
+          statusline[k], effects[k] = result, effect
+        end
+      end
+    end
+
+    local remaining = table.getn(waiting)
+    local completed = 0
+
+    local start = os.time()
+    while start + 2 > os.time() do
+      if remaining == completed then
+        break
+      end
+
+      for i = 1, remaining do
+        local wait_val = waiting[i]
+
+        if wait_val ~= nil then
+          local index, thread = wait_val.index, wait_val.thread
+          local _, res = coroutine.resume(thread, window, buffer)
+
+          if coroutine.status(thread) == 'dead' then
+            statusline[index] = res
+            -- Remove
+            completed = completed + 1
+            waiting[i] = nil
+          end
+        end
+      end
+    end
+
+    -- Filter nils and concat
+    local final = {}
+    for k, v in ipairs(statusline) do
+      if effects[k] then v = effects[k](v) end
+      if v then table.insert(final, v) end
+    end
+
+    return table.concat(final, "")
+  end
+end
+
+-- Creates a table of all window/buffers
+local get_new_windows_table = function()
+  return setmetatable({}, {__index = function(self, winid)
+    local val = setmetatable({}, {
+      __index = function(win_table, bufnr)
+
+        if not fl.generator then return function() return '' end end
+
+        local window = Window:new(winid)
+        local buffer = Buffer:new(bufnr)
+        local items = vim.tbl_flatten(fl.generator(window, buffer))
+        local p = processor(items, window, buffer)
+
+        rawset(win_table, bufnr, p)
+        return p
+      end,
+    })
+
+    rawset(self, winid, val)
+    return val
+  end,
+  })
+end
+
+-- Draws the status/tabline
+function draw_statusline(winid)
+  local bufnr = vim.api.nvim_win_get_buf(winid)
+  return fl._window_statuslines[winid][bufnr]()
+end
+function draw_tabline()
+  return fl._tabline()
+end
+
+-- Set up a statusline per window
+fl.setup_statusline = function(generator)
+  fl._window_statuslines = get_new_windows_table()
+  fl.generator = generator
+  vim.api.nvim_create_autocmd(
+    {'BufWinEnter','WinEnter'},
+    {pattern='*', callback=function()
+      vim.wo.statusline = "%!luaeval('draw_statusline("..vim.api.nvim_get_current_win()..")')"
+    end
+  })
+end
+
+-- Set up a global tabline
+fl.setup_tabline = function(generator)
+  fl._tabline = generator
+  vim.cmd('set tabline=%!v:lua.draw_tabline()')
+end
+
+return fl