refactor(offsets): use wininfo to calculate offset

fixes #789

Author: akinsho

lua/bufferline/offset.lua

@@ -10,17 +10,6 @@ local api = vim.api
 local fn = vim.fn
 local padding = constants.padding
 
-local t = {
-  LEAF = "leaf",
-  ROW = "row",
-  COLUMN = "col",
-}
-
-local supported_win_types = {
-  [t.LEAF] = true,
-  [t.COLUMN] = true,
-}
-
 ---Format the content of a neighbouring offset's text
 ---@param size integer
 ---@param highlight table<string, string>
@@ -80,57 +69,23 @@ local function guess_window_highlight(win_id, attribute, match)
   return match
 end
 
---- This helper checks to see if bufferline supports creating an offset for the given layout
---- Valid window layouts can be
---- * A list of full height splits in a row:
---- `{'row', ['leaf', id], ['leaf', id]}`
---- * A row of splits where one on either edge is not full height but the matching
---- split is on the top:
---- e.g. the vertical tool bar is split in two such as for undo tree
---- `{'row', ['col', ['leaf', id], ['leaf', id]], ['leaf', id]}`
----
----@param windows any[]
----@return boolean, number
-local function is_valid_layout(windows)
-  local win_type, win_id = windows[1], windows[2]
-  if utils.is_list(win_id) and win_type == t.COLUMN then win_id = win_id[1][2] end
-  return supported_win_types[win_type] and type(win_id) == "number", win_id
-end
-
---- Test if the windows within a layout row contain the correct panel buffer
---- NOTE: this only tests the first and last windows as those are the only
---- ones that it makes sense to add a panel for
----@param windows any[]
+---@param windows {wincol: number, winrow: number, bufnr: number, winid: number, width: number}[]
 ---@param offset table
----@return boolean
----@return number?
----@return boolean?
+---@return boolean valid
+---@return number? win_id
+---@return boolean? is_left
 local function is_offset_section(windows, offset)
-  local wins = { windows[1] }
-  if #windows > 1 then wins[#wins + 1] = windows[#windows] end
-  for idx, win in ipairs(wins) do
-    local valid_layout, win_id = is_valid_layout(win)
-    if valid_layout then
-      local buf = api.nvim_win_get_buf(win_id)
-      local valid = buf and vim.bo[buf].filetype == offset.filetype
-      local is_left = idx == 1
-      if valid then return valid, win_id, is_left end
+  local last = windows[1]
+  for _, win in ipairs(windows) do
+    if win.winrow == 2 then
+      if vim.bo[win.bufnr].filetype == offset.filetype then
+        if win.wincol > last.wincol then last = win end
+        if win.wincol == 1 then return true, win.winid, true end
+      end
     end
   end
-  return false, nil, nil
-end
-
---- Iterate over COLUMN layout by always picking the first element.
---- Assuming this is the topmost window, it's the one that should
---- dictate the tabline offset.
----@param layout any[]
----@return any[]
-local function iterate_col_layout(layout)
-  if layout[1] == t.COLUMN then
-    return iterate_col_layout(layout[2][1])
-  else
-    return layout
-  end
+  if last.wincol > 1 then return true, last.winid, false end
+  return false
 end
 
 ---@class OffsetData
@@ -151,28 +106,28 @@ function M.get()
   local total_size = 0
   local sep_hl = highlights.hl(hls.offset_separator.hl_group)
 
-  if offsets and #offsets > 0 then
-    local layout = iterate_col_layout(fn.winlayout())
+  -- wininfo tells us whether or not a window is on the top level or not of the layout
+  -- if it is on the top level and it is at the end or beginning it is an offset
+  local wininfo = vim.tbl_filter(function(win) return fn.win_gettype(win.winnr) == "" end, fn.getwininfo())
 
+  if offsets and #offsets > 0 then
     for _, offset in ipairs(offsets) do
       -- don't bother proceeding if there are no vertical splits
-      if layout[1] == t.ROW then
-        local is_valid, win_id, is_left = is_offset_section(layout[2], offset)
-        if is_valid and win_id then
-          local width = api.nvim_win_get_width(win_id) + (offset.padding or 0)
+      local is_valid, win_id, is_left = is_offset_section(wininfo, offset)
+      if is_valid and win_id then
+        local width = api.nvim_win_get_width(win_id) + (offset.padding or 0)
 
-          local hl_name = offset.highlight or guess_window_highlight(win_id) or config.highlights.fill.hl_group
+        local hl_name = offset.highlight or guess_window_highlight(win_id) or config.highlights.fill.hl_group
 
-          local hl = highlights.hl(hl_name)
-          local component = get_section_text(width, { text = hl, sep = sep_hl }, offset, is_left)
+        local hl = highlights.hl(hl_name)
+        local component = get_section_text(width, { text = hl, sep = sep_hl }, offset, is_left)
 
-          total_size = total_size + width
+        total_size = total_size + width
 
-          if is_left then
-            left, left_size = component, left_size + width
-          else
-            right, right_size = component, right_size + width
-          end
+        if is_left then
+          left, left_size = component, left_size + width
+        else
+          right, right_size = component, right_size + width
         end
       end
     end