balance sibling pane sizes in wezterm (not working)

balance.lua

--- Get panes that are on the same axis as the tab's active pane
---@param axis 'y'|'x'
---@param tab table
---@return table siblings
local function get_axis_siblings(axis, tab)
  local initial = tab:active_pane()
  local siblings = { initial }
  local prev_dir = axis == "x" and "Left" or "Up"
  local next_dir = axis == "x" and "Right" or "Down"

  local prev = tab:get_pane_direction(prev_dir)
  while prev do
    table.insert(siblings, 1, prev)
    prev:activate()
    prev = tab:get_pane_direction(prev_dir)
  end

  initial:activate() -- annoying
  local next = tab:get_pane_direction(next_dir)
  while next do
    table.insert(siblings, next)
    next:activate()
    next = tab:get_pane_direction(next_dir)
  end

  initial:activate() -- restore
  return siblings
end


---@param axis 'y'|'x'
local function balance_panes(axis)
  ---@param win table
  return function(win)
    local tab = win:active_tab()
    local initial = tab:active_pane()
    local prev_dir = axis == "x" and "Left" or "Up"
    local next_dir = axis == "x" and "Right" or "Down"
    local siblings = get_axis_siblings(axis, tab)
    local tab_size = tab:get_size()[axis == "x" and "cols" or "rows"]
    local balanced_size = math.floor(tab_size / #siblings)
    local pane_size_key = axis == "x" and "cols" or "viewport_rows"
    wezterm.log_info(
      string.format(
        "resizing %s panes on %s axis to %s cells",
        #siblings,
        axis,
        balanced_size
      )
    )

    for i, p in ipairs(siblings) do
      local pane_size = p:get_dimensions()[pane_size_key]
      local adj_amount = pane_size - balanced_size
      local adj_dir = adj_amount < 0 and next_dir or prev_dir
      adj_amount = math.abs(adj_amount)
      wezterm.log_info(
        string.format(
          "adjusting pane %s from %s by %s cells %s",
          tostring(i),
          tostring(pane_size),
          tostring(adj_amount),
          adj_dir
        )
      )
      p:activate()
      win:perform_action(
        -- AdjustPaneSize only acts on active pane
        wezterm.action.AdjustPaneSize({ adj_dir, adj_amount }),
        p -- this does not affect anything
      )
    end
    initial:activate()
  end
end

wezterm.on("augment-command-palette", function()
  return {
    {
      brief = "Balance panes horizontally",
      action = wezterm.action_callback(balance_panes("x")),
    },
  }
end)

related

• wez/wezterm#2972 feature request
• wez/wezterm#4037 helper fn - get adjacent pane for any pane
• wez/wezterm#4038 helper fn - resize any pane
• wez/wezterm#687 similar feature - on dbl click pane separator
• wez/wezterm#225 wez' lua scripting api issue