Create a Bootstrap theme

Creates a Bootstrap theme object, where you can:

Choose a (major) Bootstrap version.
Choose a Bootswatch theme (optional).
Customize main colors and fonts via explicitly named arguments (e.g., bg, fg, primary, etc).
Customize other, lower-level, Bootstrap Sass variable defaults via ....

To learn more about how to implement custom themes, as well as how to use them inside Shiny and R Markdown, see here.

Usage

bs_theme(
  version = version_default(),
  preset = NULL,
  ...,
  bg = NULL,
  fg = NULL,
  primary = NULL,
  secondary = NULL,
  success = NULL,
  info = NULL,
  warning = NULL,
  danger = NULL,
  base_font = NULL,
  code_font = NULL,
  heading_font = NULL,
  font_scale = NULL,
  bootswatch = NULL
)

bs_theme_update(
  theme,
  ...,
  preset = NULL,
  bg = NULL,
  fg = NULL,
  primary = NULL,
  secondary = NULL,
  success = NULL,
  info = NULL,
  warning = NULL,
  danger = NULL,
  base_font = NULL,
  code_font = NULL,
  heading_font = NULL,
  font_scale = NULL,
  bootswatch = NULL
)

is_bs_theme(x)

Arguments

version: The major version of Bootstrap to use (see versions() for possible values). Defaults to the currently recommended version for new projects (currently Bootstrap 5).
preset: The name of a theme preset, either a built-in theme provided by bslib or a Bootswatch theme (see builtin_themes() and bootswatch_themes() for possible values). This argument takes precedence over the bootswatch argument and only one preset or bootswatch can be provided. When no bootswatch theme is specified, and version is 5 or higher, preset defaults to "shiny". To remove the "shiny" preset, provide a value of "bootstrap" (this value will also work in bs_theme_update() to remove a preset or bootswatch theme).
...: arguments passed along to bs_add_variables().
bg: A color string for the background.
fg: A color string for the foreground.
primary: A color to be used for hyperlinks, to indicate primary/default actions, and to show active selection state in some Bootstrap components. Generally a bold, saturated color that contrasts with the theme's base colors.
secondary: A color for components and messages that don't need to stand out. (Not supported in Bootstrap 3.)
success: A color for messages that indicate an operation has succeeded. Typically green.
info: A color for messages that are informative but not critical. Typically a shade of blue-green.
warning: A color for warning messages. Typically yellow.
danger: A color for errors. Typically red.
base_font: The default typeface.
code_font: The typeface to be used for code. Be sure this is monospace!
heading_font: The typeface to be used for heading elements.
font_scale: A scalar multiplier to apply to the base font size. For example, a value of 1.5 scales font sizes to 150% and a value of 0.8 scales to 80%. Must be a positive number.
bootswatch: The name of a bootswatch theme (see bootswatch_themes() for possible values). When provided to bs_theme_update(), any previous Bootswatch theme is first removed before the new one is applied (use bootswatch = "bootstrap" to effectively remove the Bootswatch theme).
theme: A bs_theme() object.
x: an object.

Value

Returns a sass::sass_bundle() (list-like) object.

Colors

Colors may be provided in any format that htmltools::parseCssColors() can understand. To control the vast majority of the ('grayscale') color defaults, specify both the fg (foreground) and bg (background) colors. The primary and secondary theme colors are also useful for accenting the main grayscale colors in things like hyperlinks, tabset panels, and buttons.

Fonts

Use base_font, code_font, and heading_font to control the main typefaces. These arguments set new defaults for the relevant font-family CSS properties, but don't necessarily import the relevant font files. To both set CSS properties and import font files, consider using the various font_face() helpers.

Each *_font argument may be a single font or a font_collection(). A font can be created with font_google(), font_link(), or font_face(), or it can be a character vector of font names in the following format:

A single unquoted name (e.g., "Source Sans Pro").
A single quoted name (e.g., "'Source Sans Pro'").
A comma-separated list of names w/ individual names quoted as necessary. (e.g. c("Open Sans", "'Source Sans Pro'", "'Helvetica Neue', Helvetica, sans-serif"))

font_google() sets local = TRUE by default, which ensures that the font files are downloaded from Google Fonts when your document or app is rendered. This guarantees that the client has access to the font family, making it relatively safe to specify just one font family:

bs_theme(base_font = font_google("Pacifico", local = TRUE))

That said, we recommend you specify multiple "fallback" font families, especially when relying on remote and/or system fonts being available. Fallback fonts are useful not only for handling missing fonts, but also ensure that your users don't experience a Flash of Invisible Text (FOIT) which can be quite noticeable with remote web fonts on a slow internet connection.

bs_theme(base_font = font_collection(font_google("Pacifico", local = FALSE), "Roboto", "sans-serif"))

References

Get Started: Theming introduces theming with bslib in Shiny apps and R Markdown documents.
Theming: Bootstrap 5 variables provides a searchable reference of all theming variables available in Bootstrap 5.
Theming: Custom components gives a tutorial on creating a dynamically themable custom component.
bslib's theming capabilities are powered by the sass package.
Bootstrap's utility classes can be helpful when you want to change the appearance of an element without writing CSS or customizing your bs_theme().

Examples

if (FALSE) { # rlang::is_interactive()

theme <- bs_theme(
  # Controls the default grayscale palette
  bg = "#202123", fg = "#B8BCC2",
  # Controls the accent (e.g., hyperlink, button, etc) colors
  primary = "#EA80FC", secondary = "#48DAC6",
  base_font = c("Grandstander", "sans-serif"),
  code_font = c("Courier", "monospace"),
  heading_font = "'Helvetica Neue', Helvetica, sans-serif",
  # Can also add lower-level customization
  "input-border-color" = "#EA80FC"
)

bs_theme_preview(theme)

# Lower-level bs_add_*() functions allow you to work more
# directly with the underlying Sass code
theme <- bs_add_variables(theme, "my-class-color" = "red")
theme <- bs_add_rules(theme, ".my-class { color: $my-class-color }")
}