quartose (version 0.1.0)

quarto_object: Dynamically generate quarto syntax

Description

Define quarto objects for insertion into a document. Intended to be used inside a quarto document, within a knitr code chunk with the results: asis option set.

Usage

quarto_section(title, level)
quarto_tabset(content, level, title = NULL, names = NULL)
quarto_div(content, class = NULL, sep = "")
quarto_span(content, class = NULL, sep = "")
quarto_group(content, sep = "")
quarto_markdown(content, sep = "")

Value

These functions always return an object with parent S3 class "quarto_object", in addition to a specific S3 class corresponding to the function. For example, quarto_section() objects also possess the "quarto_section" class.

Arguments

title

Character string specifying the text to use as a section title. For quarto_section() this is a required argument. For quarto_tabset() it is permitted to use title = NULL, in which case the tabset will be printed without a section header above it. This is the default behavior for tabsets.

level

Numeric header level applied to section title or tabset names. The level argument must be a whole number between 1 and 6. Only relevant to quarto objects that produce section headings, specifically quarto_section() and quarto_tabset().

content

List or character vector containing content to be included within the quarto object. The expected format of the content argument differs slightly depending on which function is used. See the "details" section for more information.

names

Character vector of names to be applied to the tabs in a tabset. Only relevant to quarto_tabset(). If names = NULL, the names will be taken from the names of the content argument.

class

Character vector specifying CSS classes to be applied to the content. Only relevant to quarto_div() and quarto_span(). Defaults to class = NULL, in which case the formatted text written to the document will have a dummy CSS class "quartose-null" applied.

sep

Character string specifying the separator to be used when merging content for printing to the document. Defaults to sep = "" for all functions.

Details

The purpose of these functions is to allow the user to dynamically generate quarto syntax from R. When used within a quarto document they allow the user to generate callouts, margin text, tabsets, section headers, and other kinds of quarto output. At the current state of development the functionality is somewhat limited, discussed below.

The quarto_*() functions supplied by the quartose package have a common design: argument values supplied by the user are stored internally as a list, with only a minimum of processing done at the time that the function is called. The object is assigned to two S3 classes, the "quarto_object" shared by all objects, and a specific class associated with the calling function. These objects can be inspected and manipulated programmatically like any other R objects prior to printing.

When creating a quarto object, note that most quarto_*() functions take a content argument, which differs slightly depending on the context:

• For quarto_section() there is no `content`` argument: section headers have titles, but they do not contain content.

• For quarto_span() the `content`` argument must be a character vector, not a list.

• For quarto_div() the content`` argument is permitted to be a character vector or a list, but it will always be stored internally as a list. If the input is a list, it can contain other quarto objects. The intended use for this is a div that contains several spans, but it is not limited to this use case. At present, quarto_div()` cannot handle plot objects, but functionality may be extended to permit this in future.

• For quarto_tabset() the content argument must be a list. The list elements can be any printable R object: each element of the list will appear in its own tab. At present the support for graphics objects is limited: ggplot2 objects are captured and will only be rendered when knitr::knit_print() is called. No attempt is made (as yet!) to support other kinds of graphic objects, and if these are passed via the content argument the function will likely fail.

• For quarto_markdown() the content argument may be a character vector or a list of character vectors. The function will throw an error if other kinds of objects are passed via content.

• For quarto_group() the content argument must be a list, and all elements of the list must be quarto objects. The intended use of this function is simply to collect several quarto objects into a single group that will be printed all at the same time rather than sequentially.

Creating a quarto object only defines the data structure, it does not perform any formatting. Similarly, if the object is printed using print(), no formatting will be applied. A brief summary of the data structure will be printed to the console, no more. However, when knitr::knit_print() is called, the quarto object is first passed to the relevant format() method, which is responsible for constructing the appropriate quarto syntax. Calling format() will return a character vector or a list. If it returns a list all elements will either be character strings with the appropriate quarto syntax, or a plot object that has not yet been rendered. After formatting is applied the knitr::knit_print() method will pass the strings (or plots) to the document. For more detail on the formatting and printing methods see knit_print.quarto_object() and format.quarto_object().

Examples

# quarto_section ------------------------------------------------------

sec <- quarto_section("A level-two header", level = 2L)

# quarto objects have two classes, a general purpose class shared by 
# all quarto objects, and a class specific to the function
class(sec) 
 
# base::print() displays an abstract summary of the object 
print(sec)

# knitr::knit_print() produces the rendered quarto syntax
knitr::knit_print(sec)

# quarto_span ---------------------------------------------------------

spn1 <- quarto_span("This is plain text")
spn2 <- quarto_span("This is underlined text", class = "underline")

print(spn1)

print(spn2)

knitr::knit_print(spn1)

knitr::knit_print(spn2)

# quarto_div ----------------------------------------------------------

# quarto_div objects are flexible: they can take a character vector as
# the content argument, but can also take lists of other objects; note
# that internally the content is always represented as a list
div1 <- quarto_div("This is a callout note", class = "callout-note")
div2 <- quarto_div(
  content = list(
    quarto_span(content = "You can wrap multiple spans in a div so that"),
    quarto_span(content = "some text is highlighted", class = "mark"),
    quarto_span(content = "and some is underlined", class = "underline")
  ),
  class = c("column-margin", "callout-tip"),
  sep = " "
)

print(div1)

print(div2)

knitr::knit_print(div1)

knitr::knit_print(div2)

# quarto_tabset -------------------------------------------------------

tbs <- quarto_tabset(list(tab1 = 1:10, tab2 = "hello"), level = 3L)

print(tbs)

knitr::knit_print(tbs)

# quarto_markdown -----------------------------------------------------

mkd <- quarto_markdown(list("- a markdown", "- list"), sep = "\n")

print(mkd)

knitr::knit_print(mkd)

# quarto_group --------------------------------------------------------

grp <- quarto_group(list(
  quarto_div("This is a callout note", class = "callout-note"),
  quarto_div("This is a callout tip", class = "callout-tip")
))

print(grp)

knitr::knit_print(grp)