Formatting
Highlights
provides two output formats for highlighted source code, namely text/html
and text/latex
– both of which have been shown in previous sections of this manual. In this section we'll be describing how to go about extending Highlights
formatting to support user-defined formats.
To begin we will need to import the Format
module from Highlights
.
using Highlights: Format, highlight
Now we need to decide on a format the we'd like to add. We'll be adding an ANSI formatter that can be used to display highlighted source code in the terminal. For that we'll need to install the Crayons
package.
Pkg.add("Crayons")
using Crayons
Next we'll define a Format.render
method that will be used to highlight tokenised source code using a user-provided theme.
function Format.render(io::IO, ::MIME"text/ansi", tokens::Format.TokenIterator)
for (str, id, style) in tokens
fg = style.fg.active ? map(Int, (style.fg.r, style.fg.g, style.fg.b)) : :nothing
bg = style.bg.active ? map(Int, (style.bg.r, style.bg.g, style.bg.b)) : :nothing
crayon = Crayon(
foreground = fg,
background = bg,
bold = style.bold,
italics = style.italic,
underline = style.underline,
)
print(io, crayon, str, inv(crayon))
end
end
The io
argument to render
needs to be a subtype of IO
. To allow for more exotic "buffer"-like objects, such as push!
ing rendered tokens to a vector one can use a custom wrapper type such as
immutable BufferWrapper <: IO
buffer::IOBuffer
data::Vector{RGBA{Float32}}
end
where the source needs to be written to a buffer while the colour data has to be pushed to a separate vector of colours.
To view highlighted source code in the terminal we can then just call
julia> highlight(stdout, MIME("text/ansi"), source, Lexers.JuliaLexer)