feat(path): support floating and embedded preview for path source

README.md

@@ -1409,6 +1409,10 @@ each sources.
       })
     end
     ```
+  - `opts.sources.path.preview`: `"floating"` | `"previous"`
+    - Default: `"previous"`
+    - `"previous"` will preview the buffer in the menu's previous split window, like TS/LSP symbols.
+    - `"floating"` will preview the buffer in a popup winow adjacent to the menu.
 
 ##### Treesitter
 
@@ -1942,12 +1946,14 @@ Declared and defined in [`lua/dropbar/menu.lua`](https://github.com/Bekaboo/drop
 | ------             | ------                                            | ------                                                                                 |
 | `buf`              | `integer`                                         | buffer number of the menu                                                              |
 | `win`              | `integer`                                         | window id of the menu                                                                  |
+| `preview_win`      | `integer`                                         | window id being used for preview, if any                                               |
 | `is_opened`        | `boolean?`                                        | whether the menu is currently opened                                                   |
 | `entries`          | [`dropbar_menu_entry_t[]`](#dropbar_menu_entry_t) | entries in the menu                                                                    |
 | `win_configs`      | `table`                                           | window configuration, value can be a function, see [menu configuration options](#menu) |
 | `_win_configs`     | `table?`                                          | evaluated window configuration                                                         |
 | `cursor`           | `integer[]?`                                      | initial cursor position                                                                |
 | `prev_win`         | `integer?`                                        | previous window, assigned when calling new() or automatically determined in open()     |
+| `prev_buf`         | `integer?`                                        | previous buffer, assigned when calling new() or automatically determined in open()     |
 | `sub_menu`         | `dropbar_menu_t?`                                 | submenu, assigned when calling new() or automatically determined when a new menu opens |
 | `prev_menu`        | `dropbar_menu_t?`                                 | previous menu, assigned when calling new() or automatically determined in open()       |
 | `clicked_at`       | `integer[]?`                                      | last position where the menu was clicked, 1,0-indexed                                  |

lua/dropbar/configs.lua

@@ -446,6 +446,9 @@ M.opts = {
       modified = function(sym)
         return sym
       end,
+      ---Preview files in the prevous window or a floating window.
+      ---@type "previous"|"floating"
+      preview = 'previous',
     },
     treesitter = {
       -- Lua pattern used to extract a short name from the node text

lua/dropbar/menu.lua

@@ -177,12 +177,14 @@ end
 ---@class dropbar_menu_t
 ---@field buf integer?
 ---@field win integer?
+---@field preview_win integer? The open preview window, if any
 ---@field is_opened boolean?
 ---@field entries dropbar_menu_entry_t[]
 ---@field win_configs table window configuration, value can be a function
 ---@field _win_configs table evaluated window configuration
 ---@field cursor integer[]? initial cursor position
 ---@field prev_win integer? previous window, assigned when calling new() or automatically determined in open()
+---@field prev_buf integer? previous buffer, assigned when calling new() or automatically determined in open()
 ---@field sub_menu dropbar_menu_t? submenu, assigned when calling new() or automatically determined when a new menu opens
 ---@field prev_menu dropbar_menu_t? previous menu, assigned when calling new() or automatically determined in open()
 ---@field clicked_at integer[]? last position where the menu was clicked, byte-indexed, 1,0-indexed
@@ -311,6 +313,20 @@ function dropbar_menu_t:click_at(pos, min_width, n_clicks, button, modifiers)
   end
 end
 
+---Retrieves the root window of the menu.
+---If `self.prev_menu` is nil then this `self.prev_win`.
+---Otherwise, it is the root window of `self.prev_menu`.
+---@return integer?
+function dropbar_menu_t:root_win()
+  local current = self
+  local win = self.prev_win
+  while current and current.prev_menu do
+    win = current.prev_menu.prev_win
+    current = current.prev_menu
+  end
+  return win
+end
+
 ---"Click" the component in the dropbar menu
 ---Side effects: update self.clicked_at
 ---@param symbol dropbar_symbol_t

lua/dropbar/sources/path.lua

@@ -34,6 +34,155 @@ local function get_icon_and_hl(path)
   return icon, icon_hl, name_hl
 end
 
+---@param self dropbar_symbol_t
+local function preview_prepare_buf(self, path)
+  local buf
+  if vim.uv.fs_stat(path).type == 'directory' then
+    -- TODO: preview directory entries
+    self:preview_restore_view()
+    return
+  end
+  buf = vim.fn.bufnr(path, false)
+  if buf == nil or buf == -1 then
+    buf = vim.fn.bufadd(path)
+    if not buf then
+      self:preview_restore_view()
+      return
+    end
+    if not vim.api.nvim_buf_is_loaded(buf) then
+      vim.fn.bufload(buf)
+    end
+  end
+  if buf == nil or self.entry.menu == nil or self.entry.menu.win == nil then
+    self:preview_restore_view()
+    return
+  end
+  return buf
+end
+
+---@param self dropbar_symbol_t
+local function preview_open_float(self, path, icon, icon_hl)
+  local preview_buf = preview_prepare_buf(self, path)
+  if not preview_buf then
+    return
+  end
+
+  local function make_title()
+    local pat = vim.fs.normalize(
+      configs.eval(configs.opts.sources.path.relative_to, preview_buf)
+    )
+    return {
+      { icon, icon_hl },
+      {
+        vim.api
+          .nvim_buf_get_name(preview_buf)
+          :gsub('' .. pat .. '/', '')
+          :gsub('^' .. pat, ''), -- ':~'
+        'NormalFloat',
+      },
+    }
+  end
+  if
+    self.entry.menu.preview_win == nil
+    or vim.api.nvim_win_is_valid(self.entry.menu.preview_win) == false
+  then
+    self.entry.menu.preview_win = vim.api.nvim_open_win(preview_buf, false, {
+      -- relative = 'editor',
+      relative = 'win',
+      style = 'minimal',
+      -- focusable = false,
+      width = math.min(80, math.floor(vim.o.columns / 2)),
+      height = math.min(25, math.floor(vim.o.lines / 2)),
+      row = 0,
+      col = vim.api.nvim_win_get_width(self.entry.menu.win) + 1,
+      -- row = vim.api.nvim_win_get_position(self.entry.menu.win)[1],
+      -- col = vim.api.nvim_win_get_position(self.entry.menu.win)[2]
+      --   + vim.api.nvim_win_get_width(self.entry.menu.win)
+      --   + 1,
+      border = 'solid',
+      title = make_title(),
+    })
+    vim.api.nvim_create_autocmd('BufLeave', {
+      buffer = self.entry.menu.buf,
+      callback = function()
+        self:preview_restore_view()
+      end,
+    })
+    vim.schedule(function()
+      vim.api.nvim_exec_autocmds(
+        'CursorMoved',
+        { buffer = self.entry.menu.buf }
+      )
+    end)
+  else
+    vim.api.nvim_win_set_buf(self.entry.menu.preview_win, preview_buf)
+    local config = vim.api.nvim_win_get_config(self.entry.menu.preview_win)
+    config.title = make_title()
+    vim.api.nvim_win_set_config(self.entry.menu.preview_win, config)
+  end
+  vim.api.nvim_win_set_cursor(self.entry.menu.preview_win, { 1, 0 })
+  vim.wo[self.entry.menu.preview_win].winbar = ''
+  vim.wo[self.entry.menu.preview_win].stc = ''
+  vim.wo[self.entry.menu.preview_win].signcolumn = 'no'
+  vim.wo[self.entry.menu.preview_win].number = false
+  vim.wo[self.entry.menu.preview_win].relativenumber = false
+end
+
+---@param self dropbar_symbol_t
+local function preview_close_float(self)
+  if
+    self.entry.menu.preview_win
+    and vim.api.nvim_win_is_valid(self.entry.menu.preview_win)
+  then
+    vim.api.nvim_win_close(self.entry.menu.preview_win, true)
+  end
+  self.entry.menu.preview_win = nil
+end
+
+---@param self dropbar_symbol_t
+local function preview_open_previous(self, path)
+  local preview_buf = preview_prepare_buf(self, path)
+  if not preview_buf then
+    return
+  end
+  local buflisted = vim.bo[preview_buf].buflisted
+
+  self.entry.menu.preview_win = self.entry.menu:root_win()
+  self.entry.menu.prev_buf = self.entry.menu.prev_buf
+    or vim.api.nvim_win_get_buf(self.entry.menu.preview_win)
+
+  vim.api.nvim_create_autocmd('BufLeave', {
+    buffer = self.entry.menu.buf,
+    callback = function()
+      self:preview_restore_view()
+    end,
+  })
+  vim.api.nvim_win_set_buf(self.entry.menu.preview_win, preview_buf)
+  local last_exit = vim.api.nvim_buf_get_mark(preview_buf, '"')
+  if last_exit[1] ~= 0 then
+    vim.api.nvim_win_set_cursor(self.entry.menu.preview_win, last_exit)
+  end
+
+  vim.bo[preview_buf].buflisted = buflisted
+  -- ensure dropbar still shows then the preview buffer is opened
+  vim.wo[self.entry.menu.preview_win].winbar =
+    '%{%v:lua.dropbar.get_dropbar_str()%}'
+end
+
+---@param self dropbar_symbol_t
+local function preview_close_previous(self)
+  if self.win then
+    if self.entry.menu.prev_buf then
+      vim.api.nvim_win_set_buf(self.win, self.entry.menu.prev_buf)
+    end
+    if self.view then
+      vim.api.nvim_win_call(self.win, function()
+        vim.fn.winrestview(self.view)
+      end)
+    end
+  end
+end
+
 ---Convert a path to a dropbar symbol
 ---@param path string full path
 ---@param buf integer buffer handler
@@ -42,6 +191,7 @@ end
 local function convert(path, buf, win)
   local path_opts = configs.opts.sources.path
   local icon, icon_hl, name_hl = get_icon_and_hl(path)
+
   return bar.dropbar_symbol_t:new(setmetatable({
     buf = buf,
     win = win,
@@ -53,6 +203,20 @@ local function convert(path, buf, win)
     jump = function(_)
       vim.cmd.edit(path)
     end,
+    preview = vim.schedule_wrap(function(self)
+      if path_opts.preview == 'previous' then
+        preview_open_previous(self, path)
+      else
+        preview_open_float(self, path, icon, icon_hl)
+      end
+    end),
+    preview_restore_view = function(self)
+      if path_opts.preview == 'previous' then
+        preview_close_previous(self)
+      else
+        preview_close_float(self)
+      end
+    end,
   }, {
     ---@param self dropbar_symbol_t
     __index = function(self, k)
@@ -69,14 +233,16 @@ local function convert(path, buf, win)
         local parent_dir = vim.fs.dirname(path)
         self.siblings = {}
         self.sibling_idx = 1
-        for idx, name in vim.iter(vim.fs.dir(parent_dir)):enumerate() do
-          if path_opts.filter(name) then
-            table.insert(
-              self.siblings,
-              convert(parent_dir .. '/' .. name, buf, win)
-            )
-            if name == self.name then
-              self.sibling_idx = idx
+        if parent_dir then
+          for idx, name in vim.iter(vim.fs.dir(parent_dir)):enumerate() do
+            if path_opts.filter(name) then
+              table.insert(
+                self.siblings,
+                convert(parent_dir .. '/' .. name, buf, win)
+              )
+              if name == self.name then
+                self.sibling_idx = idx
+              end
             end
           end
         end