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#### 22.2.7 Tabulated List mode

Tabulated List mode is a major mode for displaying tabulated data, i.e., data consisting of entries, each entry occupying one row of text with its contents divided into columns. Tabulated List mode provides facilities for pretty-printing rows and columns, and sorting the rows according to the values in each column. It is derived from Special mode (see Basic Major Modes).

Tabulated List mode is intended to be used as a parent mode by a more specialized major mode. Examples include Process Menu mode (see Process Information) and Package Menu mode (see Package Menu in The GNU Emacs Manual).

Such a derived mode should use `define-derived-mode` in the usual way, specifying `tabulated-list-mode` as the second argument (see Derived Modes). The body of the `define-derived-mode` form should specify the format of the tabulated data, by assigning values to the variables documented below; optionally, it can then call the function `tabulated-list-init-header`, which will populate a header with the names of the columns.

The derived mode should also define a listing command. This, not the mode command, is what the user calls (e.g., `M-x list-processes`). The listing command should create or switch to a buffer, turn on the derived mode, specify the tabulated data, and finally call `tabulated-list-print` to populate the buffer.

Variable: tabulated-list-format

  This buffer-local variable specifies the format of the Tabulated List data. Its value should be a vector. Each element of the vector represents a data column, and should be a list `(name width sort)`, where

  - name is the column’s name (a string).
  - width is the width to reserve for the column (an integer). This is meaningless for the last column, which runs to the end of each line.
  - sort specifies how to sort entries by the column. If `nil`, the column cannot be used for sorting. If `t`, the column is sorted by comparing string values. Otherwise, this should be a predicate function for `sort` (see Rearrangement), which accepts two arguments with the same form as the elements of `tabulated-list-entries` (see below).

Variable: tabulated-list-entries

  This buffer-local variable specifies the entries displayed in the Tabulated List buffer. Its value should be either a list, or a function.

  If the value is a list, each list element corresponds to one entry, and should have the form `(id contents)` , where

  - id is either `nil`, or a Lisp object that identifies the entry. If the latter, the cursor stays on the same entry when re-sorting entries. Comparison is done with `equal`.
  - contents is a vector with the same number of elements as `tabulated-list-format`. Each vector element is either a string, which is inserted into the buffer as-is, or a list `(label . properties)`, which means to insert a text button by calling `insert-text-button` with label and properties as arguments (see Making Buttons).

    There should be no newlines in any of these strings.

  Otherwise, the value should be a function which returns a list of the above form when called with no arguments.

Variable: tabulated-list-revert-hook

  This normal hook is run prior to reverting a Tabulated List buffer. A derived mode can add a function to this hook to recompute `tabulated-list-entries`.

Variable: tabulated-list-printer

  The value of this variable is the function called to insert an entry at point, including its terminating newline. The function should accept two arguments, id and contents, having the same meanings as in `tabulated-list-entries`. The default value is a function which inserts an entry in a straightforward way; a mode which uses Tabulated List mode in a more complex way can specify another function.

Variable: tabulated-list-sort-key

  The value of this variable specifies the current sort key for the Tabulated List buffer. If it is `nil`, no sorting is done. Otherwise, it should have the form `(name . flip)`, where name is a string matching one of the column names in `tabulated-list-format`, and flip, if non-`nil`, means to invert the sort order.

Function: tabulated-list-init-header

  This function computes and sets `header-line-format` for the Tabulated List buffer (see Header Lines), and assigns a keymap to the header line to allow sorting entries by clicking on column headers.

  Modes derived from Tabulated List mode should call this after setting the above variables (in particular, only after setting `tabulated-list-format`).

Function: tabulated-list-print &optional remember-pos update

  This function populates the current buffer with entries. It should be called by the listing command. It erases the buffer, sorts the entries specified by `tabulated-list-entries` according to `tabulated-list-sort-key`, then calls the function specified by `tabulated-list-printer` to insert each entry.

  If the optional argument remember-pos is non-`nil`, this function looks for the id element on the current line, if any, and tries to move to that entry after all the entries are (re)inserted.

  If the optional argument update is non-`nil`, this function will only erase or add entries that have changed since the last print. This is several times faster if most entries haven’t changed since the last time this function was called. The only difference in outcome is that tags placed via `tabulated-list-put-tag` will not be removed from entries that haven’t changed (normally all tags are removed).

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