Unicode in ggplot2/shiny/markdown

server.R

library(shiny)
library(ggplot2)
library(Unicode)
library(Cairo)

TestUnicode <- function(start="25a0", end="25ff", ...)
{
  nstart <- as.hexmode(start)
  nend <- as.hexmode(end)
  r <- nstart:nend
  s <- ceiling(sqrt(length(r)))
  i <- 1:length(r)
  data.frame(x=i%%s, y=i%/%s, shape=factor(i), shapechars=-r)
}

shinyServer(function(input, output, clientData){

  output$plot <- renderPlot({
    end <- as.hexmode(input$start)+input$n
    data=TestUnicode(input$start, end)
    
    shapes <- list(1:length(data$shapechars), data$shapechars)
    
    qplot(data=data, x=x, y=y, shape=shape, size=I(5)) + 
      scale_shape_manual(values=shapes[[(input$unicode=="unicode")+1]], guide="none")
    })
  
  # A temp file to save the output.
  outfile <- tempfile(fileext='.png')
  
  output$pictureversion <- renderImage({
    width  <- 600#clientData$output_pictureversion_width
    height <- 400#clientData$output_pictureversion_height
    
    end <- as.hexmode(input$start)+input$n
    data <- TestUnicode(input$start, end)
    shapes <- list(1:length(data$shapechars), data$shapechars)
    
    png(outfile, width=width, height=height)
    qplot(data=data, x=x, y=y, shape=shape, size=I(5)) + 
      scale_shape_manual(values=shapes[[(input$unicode=="unicode")+1]], guide="none")
    dev.off()
    
    # Return a list containing the filename
    list(src = outfile,
         width = width,
         height = height,
         alt = "This is alternate text")
  }, deleteFile=FALSE)
  
  
  output$sessioninfo <- renderPrint(sessionInfo())
  output$sysinfo <- renderPrint(Sys.info())
  
  output$unicodechars <- renderPrint({
    if(input$unicode=="unicode"){
      as.u_char(as.hexmode(input$start):((as.hexmode(input$start)+input$n)))
    } else {
      1:input$n
    }
  })
  
  

#   output$filename <- renderText(outfile)
})

ui.R

library(shiny)
library(Cairo)
seed <- runif(1, 1000, 1000000)
shinyUI(fluidPage(
  titlePanel("Demonstration - Unicode Characters"),
  fluidRow(
    column(
      2,
      wellPanel(
        radioButtons("unicode", "CharacterType", choices=c("Unicode"="unicode", "R Default"="normal")),
        numericInput("n", "Number of points", value=64, min=1, max=225),
        conditionalPanel(condition="input.unicode=='unicode'",
          textInput("start", "Start value (positive)", value="25a0")
        )
      )        
    ),
    column(10,
           fluidRow(
             column(6,
                    h3("Using Graphics Device"),
                    div(align="center", plotOutput("plot", width=600, height=400))
                    ),
             column(6, 
                    h3("Using Cairo PNG"),
                    imageOutput("pictureversion"))
           ),
           br(),
           h3("Session Info"),
           verbatimTextOutput("sessioninfo"),
           br(),
           h3("System Info"),
           verbatimTextOutput("sysinfo"),
           br(),
           h3("Unicode Character Codes"),
           verbatimTextOutput("unicodechars")#,
#            br(),
#            verbatimTextOutput("filename")
    )
  )
))

Unicode.Rmd

---
title: "UnicodeTest"
author: "Susan VanderPlas"
date: "01/06/2015"
output: html_document
---

Testing whether it's a browser/rendering issue, which makes no sense to me, but it wouldn't be the strangest error I've come across: 

```{r}
library(ggplot2)
library(Unicode)
library(Cairo)

TestUnicode <- function(start="25a0", end="25ff", ...)
{
  nstart <- as.hexmode(start)
  nend <- as.hexmode(end)
  r <- nstart:nend
  s <- ceiling(sqrt(length(r)))
  i <- 1:length(r)
  data.frame(x=i%%s, y=i%/%s, shape=factor(i), shapechars=-r)
}

input <- list(unicode="unicode", start="25a0", n=256)
end <- as.hexmode(input$start)+input$n
data <- TestUnicode(input$start, end)
    
    
qplot(data=data, x=x, y=y, shape=shape, size=I(5)) + 
scale_shape_manual(values=data$shapechars, guide="none")
```