Add low-level theming customizations

Compared to higher-level theme customization available in bs_theme(), these functions are a more direct interface to Bootstrap Sass, and therefore, do nothing to ensure theme customizations are portable between major Bootstrap versions.

Usage

bs_add_variables(
  theme,
  ...,
  .where = "defaults",
  .default_flag = identical(.where, "defaults")
)

bs_add_rules(theme, rules)

bs_add_functions(theme, functions)

bs_add_mixins(theme, mixins)

bs_bundle(theme, ...)

Arguments

theme

a bs_theme() object.

...

• bs_add_variables(): Should be named Sass variables or values that can be passed in directly to the defaults argument of a sass::sass_layer().

• bs_bundle(): Should be arguments that can be handled by sass::sass_bundle() to be appended to the theme

.where

Whether to place the variable definitions before other Sass "defaults", after other Sass "declarations", or after other Sass "rules".

.default_flag

Whether or not to add a !default flag (if missing) to variable expressions. It's recommended to keep this as TRUE when .where = "defaults".

rules

Sass rules. Anything understood by sass::as_sass() may be provided (e.g., a list, character vector, sass::sass_file(), etc)

functions

A character vector or sass::sass_file() containing functions definitions.

mixins

A character vector or sass::sass_file() containing mixin definitions.

Value

a modified bs_theme() object.

Functions

• bs_add_variables(): Add Bootstrap Sass variable defaults

• bs_add_rules(): Add additional Sass rules

• bs_add_functions(): Add additional Sass functions

• bs_add_mixins(): Add additional Sass mixins

• bs_bundle(): Add additional sass::sass_bundle() objects to an existing theme.

References

https://getbootstrap.com/docs/4.4/getting-started/theming/

https://rstudio.github.io/sass/articles/sass.html#layering

Examples

# Function to preview the styling a (primary) Bootstrap button
library(htmltools)
button <- tags$a(class = "btn btn-primary", href = "#", role = "button", "Hello")
preview_button <- function(theme) {
  if (interactive()) {
    browsable(tags$body(bs_theme_dependencies(theme), button))
  }
}

# Here we start with a theme based on a Bootswatch theme,
# then override some variable defaults
theme <- bs_add_variables(
  bs_theme(bootswatch = "sketchy", primary = "orange"),
  "body-bg" = "#EEEEEE",
  "font-family-base" = "monospace",
  "font-size-base" = "1.4rem",
  "btn-padding-y" = ".16rem",
  "btn-padding-x" = "2rem"
)

preview_button(theme)

# If you need to set a variable based on another Bootstrap variable
theme <- bs_add_variables(theme, "body-color" = "$success", .where = "declarations")
preview_button(theme)

# Start a new global theme and add some custom rules that
# use Bootstrap variables to define a custom styling for a
# 'person card'
person_rules <- system.file("custom", "person.scss", package = "bslib")
theme <- bs_add_rules(bs_theme(), sass::sass_file(person_rules))
# Include custom CSS that leverages bootstrap Sass variables
person <- function(name, title, company) {
  tags$div(
    class = "person",
    h3(class = "name", name),
    div(class = "title", title),
    div(class = "company", company)
  )
}
if (interactive()) {
  browsable(shiny::fluidPage(
    theme = theme,
    person("Andrew Carnegie", "Owner", "Carnegie Steel Company"),
    person("John D. Rockefeller", "Chairman", "Standard Oil")
  ))
}