Generate an HTML report based on user interactions in shiny - html

Question

I have a shiny application that allows my user to explore a dataset. The idea is that the user explores the dataset, and any interesting things the user finds he will share with his client via email. I don't know in advance how many things the user will find interesting. So, next to each table or chart I have an "add this item to the report" button, which isolates the current view and adds it to a reactiveValues list.
Now, what I want to do is the following:
Loop through all the items in the reactiveValues list,
Generate some explanatory text describing the item (This text should preferably be formatted HTML/markdown, rather than code comments)
Display the item
Capture the output of this loop as HTML
Display this HTML in Shiny as a preview
write this HTML to a file
knitr seems to do exactly the reverse of what I want - where knitr allows me to add interactive shiny components in an otherwise static document, I want to generate HTML in shiny (maybe using knitr, I don't know) based on static values the user has created.
I've constructed a minimum not-working example below to try to indicate what I would like to do. It doesn't work, it's just for demonstration purposes.
ui = shinyUI(fluidPage(
title = "Report generator",
sidebarLayout(
sidebarPanel(textInput("numberinput","Add a number", value = 5),
actionButton("addthischart", "Add the current chart to the report")),
mainPanel(plotOutput("numberplot"),
htmlOutput("report"))
)
))
server = shinyServer(function(input, output, session){
#ensure I can plot
library(ggplot2)
#make a holder for my stored data
values = reactiveValues()
values$Report = list()
#generate the plot
myplot = reactive({
df = data.frame(x = 1:input$numberinput, y = (1:input$numberinput)^2)
p = ggplot(df, aes(x = x, y = y)) + geom_line()
return(p)
})
#display the plot
output$numberplot = renderPlot(myplot())
# when the user clicks a button, add the current plot to the report
observeEvent(input$addthischart,{
chart = isolate(myplot)
isolate(values$Report <- c(values$Report,list(chart)))
})
#make the report
myreport = eventReactive(input$addthischart,{
reporthtml = character()
if(length(values$Report)>0){
for(i in 1:length(values$Report)){
explanatorytext = tags$h3(paste(" Now please direct your attention to plot number",i,"\n"))
chart = values$Report[[i]]()
theplot = HTML(chart) # this does not work - this is the crux of my question - what should i do here?
reporthtml = c(reporthtml, explanatorytext, theplot)
# ideally, at this point, the output would be an HTML file that includes some header text, as well as a plot
# I made this example to show what I hoped would work. Clearly, it does not work. I'm asking for advice on an alternative approach.
}
}
return(reporthtml)
})
# display the report
output$report = renderUI({
myreport()
})
})
runApp(list(ui = ui, server = server))

Answer 1

You could capture the HTML of your page using html2canvas and then save the captured portion of the DOM as a image using this answer, this way your client can embed this in any HTML document without worrying about the origin of the page contents