bindCache() in a nutshell

• Similar to renderCachedPlot(), bindCache() needs the input(s) to a "pure" calculation:

r <- reactive({
  input$x + input$y
}) %>%
   bindCache(input$x, input$y)

bindCache() in a nutshell

• Similar to renderCachedPlot(), bindCache() needs the input(s) to a "pure" calculation:

r <- reactive({
  input$x + input$y
}) %>%
   bindCache(input$x, input$y)

• Should work with most existing render*() functions (some might need updates):

output$p <- renderPlotly({
  plot_ly(dat) %>% 
    filter(city %in% input$cities) %>% 
    add_lines(time, population)
}) %>%
   bindCache(input$cities)

bindCache() in a nutshell

• Similar to renderCachedPlot(), bindCache() needs the input(s) to a "pure" calculation:

r <- reactive({
  input$x + input$y
}) %>%
   bindCache(input$x, input$y)

• Should work with most existing render*() functions (some might need updates):

output$p <- renderPlotly({
  plot_ly(dat) %>% 
    filter(city %in% input$cities) %>% 
    add_lines(time, population)
}) %>%
   bindCache(input$cities)

• Same entry-point for cache configuring (now also supports {cachem} objects)

shinyOptions(cache = cachem::cache_disk("./cache"))

Custom theming!

bs_theme(
  bg = "#202123", fg = "#B8BCC2", primary = "#EA80FC",
  base_font = font_google("Grandstander")
)

font_google(), by default, tries to download, cache, and bundle the font files in one shot.

bs_theme(
  bg = "#202123", fg = "#B8BCC2", primary = "#EA80FC",
 *base_font = font_google("Grandstander")
)

How does custom theming actually work?

• bs_theme() works by overriding Bootstrap Sass variable defaults.

• Shiny will compile Sass -> CSS at run-time when necessary.
  • Can be costly, but options(sass.cache) is TRUE by default, and we default to app sub-directory on hosted platforms (see sass::sass_cache_context_dir() for details).

Bootstrap Sass provides 100s of variables!

Main colors (e.g., bg, fg, etc) "cascade" to 100s of other settings, all of which can be set via Bootstrap Sass variables (e.g., $progress-bar-bg)

bs_theme(
  bg = "#002B36", fg = "#EEE8D5", 
  "progress-bar-bg" = "orange"
)

Use with rmarkdown::html_document

--- 
output:
  html_document:
    theme:
      bg: "#202123"
      fg: "#B8BCC2"
      primary: "#EA80FC"
      base_font: !expr bslib::font_google("Grandstander")
---

• Currently requires dev version of R Markdown remotes::install_github("rstudio/rmarkdown")

• In theory, any output format building on html_document (or html_document_base) should automatically gain {bslib} support.

• Some output formats (e.g. {flexdashboard}) need updates to restructure their harded-coded CSS to Sass.

Use real-time theming w/ any Shiny app

Call bs_themer() in the server code (also works with a runtime: shiny R Markdown doc)

Implement your own theming widgets w/ setCurrentTheme()

ui <- fluidPage(
  theme = bs_theme(), 
  checkboxInput("dark_mode", "Dark mode", FALSE)
)
server <- function(input, output, session) {
  observe(session$setCurrentTheme({
    if (input$dark_mode) {
      bs_theme(bg = "black", fg = "white", primary = "purple")
    } else {
      bs_theme()
    }
  }))
}
shinyApp(ui, server)