Display a list in an Ibuffer way.
Copyright © 2021 Durand
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
A copy of the license is also available from the Free Software Foundation Web site at https://www.gnu.org/licenses/fdl.html.
The document was typeset with GNU Texinfo.
Next: Entry point, Previous: IList, Up: IList [Contents][Index]
This is a little library package that can display a list in an Ibuffer fashion. The core functionality it provides is a function that can accept a list, and produce a string showing the contents of the list according to the specifications of columns, groups, and sorters.
Next: Pixel precision, Previous: About, Up: IList [Contents][Index]
The one main function this package provides is ilist-string.
It is called as follows.
(ilist-string LIST COLUMNS GROUPS
&optional
DISCARD-EMPTY-P SORTER NO-TRAILING-SPACE SHOW-ITEM-NUM-P)
LISTThis denotes the list that the user wants to display.
COLUMNSGROUPSDISCARD-EMPTY-PThis determines whether to display empty groups or not.
SORTER ¶This is either nil, or a function with two arguments which returns non-nil if and only if the first argument should be sorted before the second argument. This is used to sort the elements in the list, before grouping happens. To sort groups, see Groups.
NO-TRAILING-SPACEIf this is non-nil then there will be no trailing whitespaces in the resulting string.
SHOW-ITEM-NUM-P ¶If this is non-nil, then each group header displays the number of items
within that group. This number is actually also stored in the text
property ilist-item-num of the group header.
Next: Groups, Previous: Entry point, Up: Entry point [Contents][Index]
Like in Ibuffer, the user can specify columns to display. Each column comprises the following specifications:
NAMEThe name to display in the header.
FUNA function that will be given the elements of the list (one at a time) that should return a string as the representation of that element in this column.
MINMAXThe minimal (resp. maximal) width this column takes.
ALIGNEither :left, :right, or :center. How the contents of the column are aligned.
ELIDE ¶If the content of an element takes more space than the MAX, whether to substitute the last few characters of that content by a fixed eliding string. If this ELIDE is not a string, then it means not to elide, but to truncate the contents.
Previous: Columns, Up: Entry point [Contents][Index]
There are two types of filter groups: the fixed and the automatic filter groups.
Next: Automatic groups, Previous: Groups, Up: Groups [Contents][Index]
Like in Ibuffer, we can group elements together in the display. One
difference with Ibuffer is that elements that are not in any group are
ignored. If one wants a "default" group, specify that explicitly. The
specifications of GROUPS are as follows.
NAMEThe name of the group. This will be enclosed in square brackets and displayed on a separate line.
FUNA function with one argument. If the function returns non-nil, then that element is considered to pertain to the group.
So a default group just uses a function that always returns t,
and is put at the end of the list GROUPS.
Empty groups might or might not be displayed, depending on the value
of DISCARD-EMPTY-P.
Next: Define automatic filter groups, Previous: Fixed groups, Up: Groups [Contents][Index]
An automatic filter group is a function that can give labels to elements in a list. These labels will be used to group elements automatically: the elements with the same label will be grouped together, automagically. Besides, an automatic filter group is also responsible for sorting group labels, and for giving a default label, if no labels are specified for some element.
To be precise, an automatic filter group is a function with the
signature: (ELEMENT &optional TYPE). The optional argument
TYPE says what the caller wants from the function:
nilIf it is omitted or nil, the function should just return the label for
ELEMENT.
defaultIf it is the symbol default, the function should return a
default label.
sorterIf it is the symbol sorter, the function should return a
function with two arguments, X and Y. This returned
function should return a non-nil value if and only if group X
should be placed earlier than group Y.
So, for example, the call (FUN t 'default) should produce the
default label, (FUN t 'sorter) should return the function used
to sort groups, and (FUN ELEMENT) should return the label for
ELEMENT, where FUN is an automatic filter group.
Previous: Automatic groups, Up: Groups [Contents][Index]
If one wants to define ones own automatic filter group, then the macro
ilist-define-automatic-group, or the shorter alias
ilist-dag, might come in handy.
In case you wonder, this dag has nothing to do with an directed acyclic graph; it is just an abbreviation to save some typing. The coincidence of the names is a misfortune.
This macro is called as follows.
(ilist-dag NAME DEFAULT SORTER &rest BODY)
NAMEThis is a string. The resulting function defined by this macro will
be named as ilist-automatic-group-NAME.
DEFAULTThis is also a string. It is used to label elements for which this automatic group returns nil as its label.
Why not just let the automatic group function give the default label instead of nil, then? Well, people make mistakes all the time, at least I do. So I think this mechanism can help people to remember give a default label for elements.
SORTERThis should be a function, or the symbol of a function.
This will be used as the sorting function of the group labels. The sorter function should accept two arguments, and should return a non-nil value if and only if the group labelled by the first argument should be displayed before the group labelled by the second argument.
Next: Mapping over lines, Previous: Entry point, Up: IList [Contents][Index]
Emacs is old, and its age shows from time to time.
As an example, Emacs usually measures lengths of strings by the numbers of characters contained in the strings. In most situations this is not a problem, but in some cases, for example when the string contains Chinese characters, this measurement is insufficient for the correct alignment inside tables.
In the beginning, I used the function string-width to measure the
widths of strings, but as its documentation says, this function only
returns an approximation to the actual width. This is changed in the
version 0.2 of the package, by the introduction of the variable
ilist-pixel-precise.
ilist-pixel-preciseIf this variable is not nil, the package works with pixels rather
than characters, and should provide better alignment and truncation. To
be more detailed, when the variable is not nil, the package uses
the function string-pixel-width to measure the widths of strings
in pixels.
Since working with actual pixels requires more computation, and as it
does not improve the user experience for users who are fine with the
approximation provided by string-width, the users should
intentionally set this variable to enable the feature.
Moreover, after version 0.3, if the value of this variable is the
symbol ‘precise’, then the paddings will use display properties to
produce pixel-exact spaces so that the alignment is precise and perfect.
See the Info node “(elisp) Display Property” for more details. For
any other non-nil values, the package uses the function round to
calculate the needed number of spaces to pad. When the number of pixels
is not a multiple of the number of pixels of a space character, some
imprecisions will follow. Therefore it is recommended to set this
variable to ‘precise’ if the user wants to set it to some non-nil
value.
However, on text terminals, precise alignment may not work as expected, as Emacs has no control over exact pixels on a text terminal (my guess).
Next: Moving, Previous: Pixel precision, Up: IList [Contents][Index]
For the convenience of package-users, this package also provides some
auxiliary functions to operate on the displayed list. One is
ilist-map-lines. Its return value is the list of execution
results on the lines over which the function is executed. By default
it skips invisible lines, but this behaviour can be alterred.
It is called as follows.
(ilist-map-lines FUN &optional PREDICATE START END NO-SKIP-INVISIBLE)
FUNThe function to execute on each matching line.
PREDICATEThis should be a function with no arguments. It will be executed on each line. If it returns non-nil, that line is considered to be matched.
STARTENDThey limit the range of the mapping.
NO-SKIP-INVISIBLEIf non-nil, then we don’t skip invisible lines.
Next: Packages using IList, Previous: Mapping over lines, Up: IList [Contents][Index]
It might be desired to move between the displayed list items in a
cyclic manner, that is, assuming the top of the buffer is
identified with the bottom of the buffer. So the package provides
four functions for moving. These functions all have an argument
NO-SKIP-INVISIBLE; if that argument is non-nil, then invisible
lines won’t skipped.
ilist-backward-lineilist-forward-lineMove between lines. One can control whether to skip group headers or to move cyclicly, through the function parameters.
ilist-backward-group-headerilist-forward-group-headerMove between group headers.
Next: Copying This Manual, Previous: Moving, Up: IList [Contents][Index]
The packages that use this library IList, which I know of, are listed here:
- BList (https://www.gitlab.com/mmemmew/blist)
If you know about other packages that use IList, or if you write a package using IList, it is welcomed to suggest to list those packages here.
Next: Index, Previous: Packages using IList, Up: IList [Contents][Index]
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