PoC of Custom Bookmarking in shiny. This example uses an in memory list to store data, but this could be replaced by calls to web API for caching data

bookmark_example.R

#
# This is a Shiny web application. You can run the application by clicking
# the 'Run App' button above.
#
# Find out more about building applications with Shiny here:
#
#    http://shiny.rstudio.com/
#

library(shiny)
library(waiter)

runid <- 0
runs <- list()
store_run_data <- function(id, x) {
    new_data <- list(x)
    names(new_data) <- as.character(id)
    runs <<- c(runs, new_data)
}
fetch_run_data <- function(id) {
    runs[[as.character(id)]]
}
# Define UI for application that draws a histogram
ui <- fluidPage(
    use_waiter(),
    # Application title
    titlePanel("Old Faithful Geyser Data"),

    # Sidebar with a slider input for number of bins 
    sidebarLayout(
        sidebarPanel(
            sliderInput("bins_input",
                        "Number of bins:",
                        min = 1,
                        max = 50,
                        value = 30),
            
            actionLink('bookmark', 'Bookmark application', icon = icon('share-alt'))
        ),

        # Show a plot of the generated distribution
        mainPanel(
           plotOutput("distPlot")
        )
    )
)

# Define server logic required to draw a histogram
server <- function(input, output, session) {
    observeEvent(input$bookmark, {
        # snapshot application state
        snapshot_state = reactiveValuesToList(input)
        # only bookmark inputs
        snapshot_state = snapshot_state[stringr::str_detect(names(snapshot_state), '_input')]
        # add the current system time to get a unique hash
        snapshot_state[['time']] = Sys.time()
        # create a state id
        runid <<- runid + 1
        store_run_data(runid, snapshot_state)
        # update the query string for the user
        
        updateQueryString(paste0('?run=', runid), mode = 'push')
        
    })
    observeEvent(getQueryString(), once = TRUE, {
        # get query string
        waiter_show(
            html = spin_fading_circles() 
        )
        
        current_run <- getQueryString()
        if(length(current_run) > 0) {
            # get bookmark from database table
            bookmark_list <- fetch_run_data(current_run$run) 
            # simulate average query time
            #Sys.sleep(1)
            # coerce JSON to R list
            #bookmark_list = jsonlite::fromJSON(bookmark$STATE_DATA)
            for(id in names(bookmark_list)) {
                value = bookmark_list[[id]]
                if(length(value) == 0) {
                    html_value = ''
                } else {
                    html_value = value
                }
                # update inputs in UI
                session$sendInputMessage(id, list(value = html_value))
            }
        }
        waiter_hide()
    })
    
    
    output$distPlot <- renderPlot({
        # generate bins based on input$bins from ui.R
        x    <- faithful[, 2]
        bins <- seq(min(x), max(x), length.out = input$bins_input + 1)

        # draw the histogram with the specified number of bins
        hist(x, breaks = bins, col = 'darkgray', border = 'white')
    })
    
}

# Run the application 
shinyApp(ui = ui, server = server)