有条件地格式化 Shiny 中 rHandsontable 中的空单元格

Question

Q1: I would like to change the format of a rhandsontable cell in Shiny when its content become empty. I thought I found it using hot_cols(renderer = "...") but I am quite surprised of the result: cells with content 0 are also highlighted. Could someone tell me how should I test emptyness in JS through R? I tried value === '' and isEmpty() without any success.

Q2: Additionnally, if we enter "1e6" in column 3, the value which appears is indeed 1000000 but its background switch to red: any way to prevent it? ie to allow scientific notation input?

Here's a minimal reproductible example:

library(shiny)
library(rhandsontable)

DF <- data.frame(col1 = c(1, 0, 3), col2 = c(letters[23:22], NA), col3 = round(rnorm(3, 1e6, 1e3),0))

server <- shinyServer(function(input, output, session) {
  
  output$rt <- renderRHandsontable({
    rhandsontable(DF) %>%      
      
      # conditional overall formatting > grey empty cells
      hot_cols(renderer = "
           function (instance, td, row, col, prop, value, cellProperties) {
             Handsontable.renderers.NumericRenderer.apply(this, arguments);
             if(!value) {
                td.style.background = '#EEE';
              }
           }")
  })
})

ui <- shinyUI(fluidPage(
  rHandsontableOutput("rt")
))

shinyApp(ui, server)

Answer 1

Regarding your first question: you can add the condition that the value is not 0:

library(shiny)
library(rhandsontable)

DF <- data.frame(col1 = c(1, 0, 3), col2 = c(letters[23:22], NA), col3 = round(rnorm(3, 1e6, 1e3),0))

server <- shinyServer(function(input, output, session) {
  
  output$rt <- renderRHandsontable({
    rhandsontable(DF) %>%      
      
      # conditional overall formatting > grey empty cells
      hot_cols(renderer = "
           function (instance, td, row, col, prop, value, cellProperties) {
             Handsontable.renderers.NumericRenderer.apply(this, arguments);
             if(!value && value != 0) {
                td.style.background = '#EEE';
              }
           }")
  })
})

ui <- shinyUI(fluidPage(
  rHandsontableOutput("rt")
))

shinyApp(ui, server)

Regarding your second question: it's a known bug that was only fixed in handsontable 6.2.1, but the CRAN version of rhandsontable uses handsontable 6.1.1. The development version seems to be updated to 6.2.2, so you could install it from https://github.com/jrowen/rhandsontable