How to solve encoding issues in a shiny app - r

Question

Any tips to solve encoding problem. I am not able to generate the up (↑) and down (↓) arrows in the code below. When running, the following warning message appears:
Warning messages:
1: unable to translate 'Maximize <U+2191>' to native encoding
2: unable to translate 'Minimize <U+2193>' to native encoding
library(shiny)
ui <- fluidPage(
sidebarLayout(
sidebarPanel(
fluidRow(
column(
width = 6,
selectInput("maxmin", label = h5("Maximize or Minimize"),
choices = list("Maximize \u2191" = 1, "Minimize \u2193" = 2), selected = "")
)
)),
mainPanel(
))
)
server <- function(input, output, session) {
}
shinyApp(ui = ui, server = server)

Answer 1

You can use HTML code for the arrows and proceed like this:
library(shiny)
choicesNames <- list("Minimize", "Maximize")
choicesHTML <- list("Minimize ↓", "Maximize ↑")
choices <- setNames(choicesNames, choicesHTML)
ui <- fluidPage(
selectizeInput("select", label = "Select", choices = NULL),
textOutput("txt")
)
server <- function(input, output, session) {
updateSelectizeInput(
session, "select",
choices = choices,
options = list(render = I("
{
item: function(item, escape) { return '<div>' + item.label + '</div>'; },
option: function(item, escape) { return '<div>' + item.label + '</div>'; }
}
"))
)
output$txt <- renderText({
paste("You chose", input$select)
})
}
shinyApp(ui, server)
Another option is to use my package shinySelect and fontawesome icons for the arrows.
library(shiny)
library(shinySelect)
library(bslib)
library(fontawesome)
choices <- HTMLchoices(
labels = list(
tags$span("Minimize", fa_i("arrow-alt-circle-down")),
tags$span("Maximize", fa_i("arrow-alt-circle-up"))
),
values = list("minimize", "maximize")
)
styles <- list(
borderBottom = "5px solid orange",
color = list(selected = "lime", otherwise = "pink"),
backgroundColor = list(selected = "cyan", otherwise = "seashell")
)
ui <- fluidPage(
theme = bs_theme(version = 4),
titlePanel("shinySelect example"),
selectControlInput(
"inputid",
label = tags$h1("Make a choice", style = "color: red;"),
optionsStyles = styles,
choices = choices,
selected = "minimize",
multiple = FALSE,
animated = TRUE
),
br(),
verbatimTextOutput("textOutput")
)
server <- function(input, output, session) {
output$textOutput <- renderPrint({
sprintf("You selected: %s", input$inputid)
})
}
shinyApp(ui, server)

Answer 2

This is an alternate solution. Solutions provided by #Stephane Laurent are great. To translate unicode points to UTF-8, you can use chr_unserialise_unicode() from rlang package. Try this
library(shiny)
library(rlang)
ll <- chr_unserialise_unicode("<U+2193>")
uu <- chr_unserialise_unicode("<U+2191>")
choicesNames <- list(1,2)
choiceValues <- list(sprintf("Minimize %s",ll),sprintf("Maximize %s",uu))
choices <- setNames(choicesNames, choiceValues)
ui <- fluidPage(
selectInput("maxmin", label = h5("Maximize or Minimize"), choices = NULL),
textOutput("mytxt")
)
server <- function(input, output, session) {
updateSelectInput(session, "maxmin", choices = choices )
output$mytxt <- renderText({
paste("You chose", input$maxmin)
})
}
shinyApp(ui = ui, server = server)