Leo’s Reference ¶

This chapter is a reference for all of Leo’s directives.

This chapter does not teach how to use Leo. It assumes you are thoroughly familiar with Leo’s tutorial.

Contents

Leo’s Reference

Part 1: @<file> directives ¶

This section discusses the @<file> directives. These directives create or import external files.

Important: Newcomers to Leo should create external files with @auto or @file. Use @auto if your external files must not contain sentinel lines. Use @file otherwise. In particular, @file is highly recommended when sharing external files in a collaborative environment.

Note: All these directive must appear in headlines.

The following table summarizes the various ways of creating external files.

Kind	Sentinels in external file?	Sections and @others expanded on write?	File data stored in .leo file?
@asis	no	no	yes
@auto	no	yes	no
@edit	no	yes: note 3	no
@nosent	no	yes	yes
@shadow	Note 1	yes	no
@file @thin Note 2	yes	yes	no

Note 1: @shadow nodes create two files, a public file without sentinels and a private file with sentinels.

Note 2: @file and @thin nodes are synonyms.

Note 3: Outline structure created in @edit nodes is not saved in the external file.

Within @path and @<file> paths, {{exp}} gets evaluated with the following symbols known: c, g, p, os and sys. For example:

@file {{os.path.abspath(os.curdir)}}/abc.py

refers to the file abc.py in (absolute path of) the current directory.

@asis <path>¶

The @asis directive creates an external file without sentinels and without any expansions.

Use this directive only when you must have complete control over every character of the external file. When writing @asis nodes, writes the body text of all nodes in outline order. Leo writes the body text as is, without recognizing section definitions, without expanding section references, and without treating directives specially in any way. In particular, Leo copies all directives, including @ or @c directives, to the external file as text.

The @@ convention: Within @asis trees only, if a headline starts with @@, Leo writes everything in the headline following the @@ just before the corresponding body text.

Files created from @asis trees contain nothing not contained in body text (or @@ headlines). In particular, if body text does not end in a newline, the first line from the next node will concatenated to the last line of the preceding node.

Within @asis trees, Leo writes no sentinels to the external file, so Leo can not update the outline using changes to the external file. When reading .leo files, Leo does not read external files created from @asis nodes. Instead, all data in an @asis tree is stored in the .leo file.

Within @asis trees, Leo recognizes the @ignore directive only in the ancestors of @asis nodes. This allows you to use the @ignore directive to prevent Leo from writing @asis trees.

Note: @file-asis and @silent are deprecated synonyms for @asis.

@auto <path>¶

The @auto directive imports an external file into a tree of nodes. Using @auto is highly recommended when using external files that must not contain Leo sentinels.

@auto trees allow people to use Leo in collaborative environments without using sentinels in external files. Even without sentinels, @auto trees can change when the corresponding external file changes outside of Leo.

When reading @auto nodes, Leo creates the @auto tree using importers, parsers that create an outline with nodes for each class, method and function in the external file. Some importers create other kinds of nodes as well.

Importers presently exist for C, elisp, HTML, .ini files, Java, Javascript, Pascal, PHP, Python and xml. Leo determines the language using the file’s extension. If no parser exists for a language, Leo copies the entire body of the external file into the @auto node.

Note: the @data import_xml_tags setting specifies the organizer tags that cause the HTML and XML importers to create outline nodes. By default, the organizer tags are html, body, head, and div.

When writing @auto nodes, Leo writes the external file without sentinels. This allows you to use Leo in collaborative environments without disturbing colleagues. Leo does not expand section references when writing @auto nodes: Leo generates @verbatim sentinels for lines that look like section references.

When importing files into @auto trees, Leo performs several checks to ensure that writing the imported file will produce exactly the same file. These checks can produces errors or warnings. Errors indicate a potentially serious problem. Leo inserts an @ignore directive in the @auto tree if any error is found. This prevents the @auto tree from modifying the external file.

Before importing a file, Leo regularizes the leading whitespace of all lines of the original source file. That is, Leo converts blanks to tabs or tabs to blanks depending on the value of the @tabwidth directive in effect for the @auto node. Leo also checks that the indentation of any non-blank line is a multiple of the indentation specified by the @tabwidth directive. Strict languages are languages such as Python for which leading whitespace must be preserved exactly as it appears in the original source file. Problems during regularizing whitespace generate errors for strict languages and warnings for non-strict languages.

After importing a file, Leo verifies that writing the @auto node would create the same file as the original file. Such file comparison mismatches generate errors unless the problem involves only leading whitespace for non-strict languages. Whenever a mismatch occurs the first non-matching line is printed.

File comparison mismatches can arise for several reasons:

Bugs in the import parsers. Please report any such bugs immediately.
Underindented lines in classes, methods or function.

An underindented line is a line of body text that is indented less then the starting line of the class, method or function in which it appears. Leo outlines can not represent such lines exactly: every line in an external file will have at least the indentation of any unindented line of the corresponding node in the outline. Leo will issue a warning (not an error) for underindented Python comment lines. Such lines can not change the meaning of Python programs.

@edit <path>¶

The @edit directive imports an external file into a single node.

When reading @edit nodes, Leo reads the entire file into the @edit node. Lines that look like sentinels will be read just as they are.

When writing @edit nodes, Leo writes expands section references, @all and @others just as with @file trees. However, Leo writes no sentinels, so the structure created by sections references, @all and @others is not preserved.

@file <path> (aka @thin)¶

The @file directive creates an external file containing sentinels. When writing @file trees, Leo expands section references and @all and @others directives.

When reading external files created by @file, the sentinels allow Leo to recreate all aspects of the outline. In particular, Leo can update the outline based on changes made to the file by another editor.

Important: @file is the recommended way to create and edit most files. In particular, using @file nodes is highly recommended when sharing external files in a collaborative environment.

The @thin directive is a synonym for @file.

Prior to Leo 4.7, @file worked differently from @thin. This should not be a problem: Leo 4.7 can read all external files written by Leo 4.6.

@nosent <path>¶

The @nosent <filename> creates an external file without sentinel lines.

When writing an @nosent tree, Leo expands section references, @all and @others directives, but Leo writes no sentinels to the external file. Thus, Leo can not update @nosent trees from changes made to the external file.

When reading an @nosent node, Leo does not read the external file. Instead, all the data in the @nosent tree is stored in the .leo file.

Note: @auto or @shadow are usually better choices than @nosent for creating external files without sentinels.

Note: The @bool force_newlines_in_at_nosent_bodies setting controls whether Leo writes a trailing newline if non-empty body text does not end in a newline. The default is True.

@shadow <path>¶

The @shadow directive creates two external files, a public file without sentinels, and a private file containing sentinels.

When reading an @shadow node, Leo uses a brilliant algorithm devised by Bernhard Mulder that compares the public and private files, and then updates the outline based on changes to the public file. In this way, @shadow provides many of the benefits of @file trees without writing sentinels in the (public) external file.

Leo can do an initial import of @shadow trees by parsing the corresponding public file, exactly as is done for @auto nodes.

Part 2: @all and @others ¶

These control how Leo places text when writing external files. They are two of the most important directives in Leo.

@all

Copies all descendant nodes to the external file. Use @all to place unrelated data in an external file.

The @all directive is valid only in the body of @file trees.

Within the range of an @all directive, Leo ignores the @others directive and section references, so Leo will not complain about orphan nodes.

@others

Writes the body text of all unnamed descendant into the external file, in outline order.

Whitespace appearing before @others directive adds to the indentation of all nodes added by the @others directive.

A single node may contain only one @others directive, but descendant nodes may have other @others directives.

Part 3: Syntax coloring directives ¶

The @color, @killcolor, @nocolor and @nocolor-node directives control how Leo colors text in the body pane.

These directives typically affect the node in which they appear and all descendant nodes. Exception: an ambiguous node, a node containing both @color and @nocolor directives, has no effect on how Leo colors text in descendant nodes.

@color

Enables syntax coloring until the next @nocolor directive.

@killcolor

Disables syntax coloring in a node, overriding all @color, @nocolor or @nocolor-node directives in the same node.

@nocolor

Disables syntax coloring until the next @nocolor directive.

@nocolor-node

Disables coloring for only the node containing it. The @nocolor-node directive overrides the @color and @nocolor directives within the same node.

Part 4: Dangerous directives ¶

These directives alter how Leo represents data in external files. They are dangerous–mistakes in using these sentinels can make it impossible for Leo to read the resulting external file. Use them with care!

Nevertheless, these sentinels can be useful in special situations.

@comment <1, 2 or three comment delims>

Sets the comment delimiters in @file and @shadow files. Important: Use @comment for unusual situations only. In most cases, you should use the @language directive to set comment delimiters.

The @comment directive may be followed by one, two or three delimiters, separated by whitespace. If one delimiter is given, it sets the delimiter used by single-line comments. If two delimiters are given, they set the block comment delimiter. If three delimiters are given, the first sets the single-line-comment delimiter, and the others set the block-comment delimiters.

Within these delimiters, underscores represent a significant space, and double underscores represent a newline. Examples:
@comment REM_
@comment __=pod__ __=cut__
The second line sets PerlPod comment delimiters.

Warning: the @comment and @delims directives must not appear in the same node. Doing so may create a file that Leo can not read.

Note: @language and @comment may appear in the same node, provided that @comment appears after the @language directive: @comment overrides @language.

The @comment directive must precede the first section name or @c directive.

@delims <1 or 2 comment delims>

Sets comment delimiters in external files containing sentinel lines.

The @delims directive requires one or two delimiters, separated by whitespace. If one delimiter is present it sets the single-line-comment delimiter. If two delimiters are present they set block comment delimiters.

This directive is often used to place Javascript text inside XML or HTML files. Like this:
@delims /* */
Javascript stuff
@delims <-- -->
HTML stuff
Warning: you must change back to previous delimiters using another @delims directive. Failure to change back to the previous delimiters will thoroughly corrupt the external file as far as compilers, HTML renderers, etc. are concerned. Leo does not do this automatically at the end of a node.

Warning: the @comment and @delims directives must not appear in the same node. Doing so may create a file that Leo can not read.

Note: The @delims directive can not be used to change the comment strings at the start of the external file, that is, the comment strings for the @+leo sentinel and the initial @+body and @+node sentinels.

@raw and @end_raw

@raw starts a section of “raw” text that ends only with the @end_raw directive or the end of the body text containing the @raw directive. Within this range, Leo ignores all section references and directives, and Leo generates no additional leading whitespace.

Part 5: All other directives ¶

This section is a reference guide for all other Leo directives, organized alphabetically.

Unless otherwise noted, all directives listed are valid only in body text, and they must start at the leftmost column of the node.

@ and @doc

These directives start a doc part. @doc is a synonym for @. Doc parts continue until an @c directive or the end of the body text. For example:
@ This is a comment in a doc part.
Doc parts can span multiple lines.
The next line ends the doc part
@c
When writing external files, Leo writes doc parts as comments.

Leo does not recognize @ or @doc in @asis trees or when the @all or @delims directives are in effect.

@c and @code

Ends any doc part and starts a code part.

@code is a deprecated synonym for @.

Leo does not recognize this directive in @asis trees or when the @all or @raw directives are in effect.

@chapter and @chapters

An @chapter tree represents a chapter. All @chapter nodes should be contained in an @chapters node.

These directives are too complex to describe here. For full details, see Using Chapters.

These directives must appear in the node’s headline.

@encoding <encoding>

Specifies the Unicode encoding for an external file. For example:
@encoding iso-8859-1
When reading external files, the encoding given must match the encoding actually used in the external file or “byte hash” will result.

@first <text>

Places lines at the very start of an external file, before any Leo sentinels. @first lines must be the very first lines in an @<file> node. More then one @first lines may appear.

This creates two first lines, a shebang line and a Python encoding line:
@first #! /usr/bin/env python
@first # -*- coding: utf-8 -*-
Here is a perl example:
@first #!/bin/sh -- # perl, to stop looping
@first eval 'exec /usr/bin/perl -w -S $0 ${1+"$@"}'
@first     if 0;

@ignore

Tells Leo to ignore the subtree in which it appears.

In the body text of most top-level @<file> nodes, the @ignore directive causes Leo not to write the tree. However, Leo ignores @ignore directives in @asis trees.

Plugins and other parts of Leo sometimes @ignore for their own purposes. For example, Leo’s unit testing commands will ignore trees containing @ignore. In such cases, the @ignore directive may appear in the headline or body text.

@language <language name>

Specifies the language in effect, including comment delimiters. If no @language directive is in effect, Leo uses the defaults specified by the @string target-language setting.

A node may contain at most one @language directive.

The valid language names are: actionscript, ada, autohotkey, batch, c, config, cpp, csharp, css, cweb, elisp, forth, fortran, fortran90, haskell, haxe, html, ini, java, javascript, kshell, latex, lua, noweb, pascal, perl, perlpod, php, plain, plsql, python, rapidq, rebol, rest, rst, ruby, shell, tcltk, tex, unknown, unknown_language, vim, vimoutline, xml, xslt.

Note: Shell files have comments that start with #.

Case is ignored in the language names. For example, the following are equivalent:
@language html
@language HTML
The @language directive also controls syntax coloring. For language x, the file leo/modes/x.py describes how to colorize the language. To see the languages presently supported, look in the leo/modes directory. There are over 100 such languages.

@last <text>

Places lines at the very end of external files.

This directive must occur at the very end of top-level @<file> nodes. More than one @last directive may exist. For example:
@first <?php
...
@last ?>
Leo does not recognize @last directive in @asis trees.

@lineending cr/lf/nl/crlf

Sets the line endings for external files. This directive overrides the @string output_newline setting.

The valid forms of the @lineending directive are:

@lineending nl The default, Linux.

@lineending cr Mac

@lineending crlf Windows

@lineending lf Same as ‘nl’, not recommended

@lineending platform Same as platform value for output_newline setting.

@nowrap

Disables line wrapping the Leo’s body pane.

Only the first @wrap or @nowrap directive in a node has any effect.

@nowrap may appear in either headlines or body text.

@pagewidth <n>

Sets the page width used to break doc parts into lines. <n> should be a positive integer. For example:
@pagewidth 100
The @pagewidth directive overrides the @int page_width setting.

@path <path>

Sets the path prefix for relative filenames for all @<file> tree.

This directive may appear in headlines or body text, and may appear in top-level @<file> nodes.

The path is an absolute path if it begins with c:\ or /, otherwise the path is a relative paths.

Multiple @path directives may contribute to the path prefix. Absolute paths overrides any ancestor @path directives. Relative paths add to the path prefix.

If no @path directives are in effect, the default path prefix is the directory containing the .leo file.

Within @path and @<file> paths, {{exp}} gets evaluated with the following symbols known: c, g, p, os and sys. For example:
@file {{os.path.abspath(os.curdir)}}/abc.py
refers to the file abc.py in (absolute path of) the current directory.

@tabwidth <n>

Sets the width of tabs. Negative tab widths cause Leo to convert tabs to spaces.

@wrap

Enables line wrapping in Leo’s body pane.

Only the first @wrap or @nowrap directive in a node has any effect.

@wrap may appear in either headlines or body text.