Glyph - Defining Custom Macros

Glyph was created wih extensibility in mind. You can freely extend Glyph Language by creating or overriding macros, to do whatever you like. Macro definitions are written in pure Ruby code and placed in .rb files within the lib/macros/ folder of your project.

Alternative Ways to Define Macros

You can also define macros:

inside your document, using the macro: macro.
Using the include macro specifying the path to an .rb file containing macro definitions stored in the lib/ directory (useful especially when compiling single Glyph files).

This is the source code of a fairly simple macro used to format a note:

1macro :note do
2  %{<div class="#{@name}"><span class="note-title">#{@name.to_s.capitalize}</span>
3    #{@value}
4
5    </div>}
6end

The macro method takes a single Symbol or String parameter, corresponding to the name of the macro. In this case, the entire block (or body of the macro) is a String corresponding to what we want the macro to evaluate to: a <div> tag containing a note.

The body of the macro is evaluated in the context of the Glyph::Macro class, therefore its instance variables (like @name or @value) can be used directly.

Why using @name instead of just “note”?

For the note macro, it absolutely makes no difference. However, by using @name it is possible to re-use the same code for the tip, important and caution macros as well, which are in fact only aliases of the note macro.

The following table lists all the instance variables that can be used inside macros:

Variable	Description
`@node`	A `Glyph::MacroNode` containing information about the macro. Useful for accessing parent and child macros, and the current `Glyph::Document`. Normally, instances of the `MacroNode` class contain the following keys: `:name`, the name of the macro. `:source`, a `String` identifying the source of the macro (a file, a snippet, etc.) `:value`, the value of the macro (populated after the document has been parsed and analyzed). `:escape`, whether the macro is a quoting macro or not. `:document`, the instance of `Document` the macro is contained in (populated after the document has been parsed and analyzed). Note that the first two keys can also be accessed via instance variables.
`@name`	The name of the macro.
`@source_name`	A `String` identifying the source of the macro (a file, a snippet, etc.).
`@source_topic`	A `String` identifying the source topic of the macro.
`@source_file`	A `String` identifying the source file of the macro.

Representations ⇈

There’s a small problem with the code used to define the note macro in the previous section: what if I want to format notes using HTML5 instead of HTML, or another output format?

Glyph supports different output formats, therefore macros must be format-independent! In fact, this is the actual source of the note macro:

1macro :note do
2  @data[:name] = @name
3  @data[:text] = value
4  render
5end

The HTML representation of the note macro is defined in the macros/reps/html.rb file as follows:

1rep :note do |data|
2  css_class = data[:name].to_s.match(/[a-z0-9_-]/i) ? data[:name] : "note"
3  %{<div class="#{css_class}">
4<span class="note-title">#{data[:name].to_s.capitalize}</span>#{data[:text]}
5
6</div>}
7end

The HTML5 representation of the note macro, on the other hand, is defined in the macros/reps/html5.rb file as follows:

1rep :note do |data|
2  css_class = data[:name].to_s.match(/[a-z0-9_-]/i) ? data[:name] : "note"
3  %{<aside class="#{css_class}">
4<span class="note-title">#{data[:name].to_s.capitalize}</span>#{data[:text]}
5
6</aside>}
7end

Note the different tags used to render the note.