Using bslib variables to stylize shiny

# Using `bslib` variables to stylize shiny

    library(bslib, warn.conflicts = FALSE)
    library(rlang)
    library(dplyr, warn.conflicts = FALSE)

# Introduction

In this example we will start by adding styles to a ‘Figma’ file. Then we will use these variables to define the high level `bslib` variables used for stylizing Shiny applications.

## Initial Steps

In order to get style data from a ‘Figma’ file using the REST API the following steps should followed:

1. Create a Figma team

2. Create a Figma file and move it to the Figma team

3. Add your favorite styles (they should appear in the Design selection at the top right of your screen)

4. Click Assets on the top left and select the book icon to publish your styles.

## Adding Bootstrap variables - `bslib`

The `bslib` library allows to manipulate the theme of a shiny application using bootstrap variables. In these example we demonstrate how to use high level bootstrap variables to stylize your application.

The high level bootstrap variables are the arguments of the functions `bslib::bs_theme`.

    rlang::fn_fmls_names(bslib::bs_theme) %>%
      tail(-3)
    #>  [1] "bg"           "fg"           "primary"      "secondary"    "success"
    #>  [6] "info"         "warning"      "danger"       "base_font"    "code_font"
    #> [11] "heading_font" "font_scale"   "bootswatch"

By using these names as style names into a ‘Figma’ file we can directly manipulate the theme of the Application.

Open the ‘Figma’ file and insert the styles of your choice using `blib` variable names as printed from the previous chunk. On the right hand side of your screen you should get a View similar to the following:

Figma file with bslib variables

After defining some of the variables that you want to modify navigate to the top left and select Assets. Then, push the book button to publish the changes on the file. Now the file is ready to be accessed from an R session using `Rigma`.

## Extract data to R

We can access published data via ‘Figma’ REST API. Find the file id in the URL of the ‘Figma’ file. Then, collect style data:

    file_key <- "sFHgQh9dL6369o5wrZHmdR" #add your own file_key
    style_data <- file_key %>%
      Rigma::get_file_styles() %>%
      Rigma::as_design_tibble()

The color is encoded in thumbnail URLs provided by the API (alternatively you can get color metadata from node ids and using the `Rigma::get_file_nodes()` method). For this tutorial, we include an example function that collects color data using the thumbnail URLs, `add_color()`. We can get high level `bslib` color variables by executing:

    bslib_palette <- style_data %>%
      Rigma::add_color() %>%
      Rigma::extract_bslib_palette()

### Text data

Metadata about text can be extracted using the following function:

    text_data <- Rigma::text_data_from_styles(style_data)

    #get base_font Figma style variable - see also snapshot
    base_font <- text_data %>%
      filter(name == "base_font") %>%
      pull(fontFamily) %>%
      font_google()

### Creating `bs_theme` object

Collecting the font and color data we can create the `bs_theme` object that can be used to stylize a shiny app

    bslib_vars <- bslib_palette %>%
      append(
        list(base_font = base_font)
      )
    rigma_theme <- exec(bs_theme, !!!bslib_vars)

and the shiny app should read

    library(shiny)
    ui <- navbarPage(
      theme = rigma_theme,
      ...
    )
    shinyApp(ui, function(...) {})