title: Letter partially disappearing when exporting text using CairoPNG
body: <p>I'm trying to construct a chart using ggplot which I am then saving to PNG image using the Cairo package's CairoPNG function.</p>
  
  <p>The problem is that the resulting image file seems to be missing chunks of the letter J on the x axis. This is a bit of an issue when I'm using month name as the x axis label.</p>
  
  <p>This only seems to happen when the text size is set to a whole number (such as 12). If I set it to 11.5 or 12.5 then the letters display fine.</p>
  
  <p>So, I can fix it by altering the font size but it feels like a bit of a hack. Does anyone know why it's behaving like this?</p>
  
  <p><img src="https://i.stack.imgur.com/4h87e.png" alt="enter image description here"></p>
  
  <p>Code is as follows:</p>
  
  <pre><code>library("ggplot2")
  library("scales")
  library("Cairo")
  
  # Set chart values
  line.width = 1
  font.size = 12
  
  # Generate some random data
  start.date &lt;- as.Date("2011-07-01")
  x.month &lt;-seq.Date(start.date, by = "month", length.out = 24)
  end.date &lt;- max(x.month)
  
  
  x.value &lt;- rnorm(24,mean=50,sd=2)
  
  # Combine into dataframe
  x.data &lt;- data.frame(
    "Month" = x.month,
    "Value" = x.value
    )
  
  # Build chart
  p &lt;- ggplot(data=x.data, aes(Month, Value)) + geom_line(size=line.width)
  p &lt;- p + theme_bw()
  p &lt;- p + ggtitle("Test Chart\n")
  p &lt;- p + scale_y_continuous(limits = c(40, 60))
  p &lt;- p + scale_x_date(limits=c(start.date+20,end.date-20), breaks = "1 month",labels = date_format("%b-%y"))
  p &lt;- p + theme(axis.text.x=element_text(angle=90, hjust=1, vjust=0.5, size=font.size),
                  axis.text.y=element_text(size=font.size),
                  axis.title.x=element_blank(),
                  axis.title.y=element_blank())
  
  # Export chart
  CairoPNG("c:\\temp\\temp1.png", width=500, height = 250)
  p
  dev.off()
  </code></pre>
  
  <hr>
  
  <p><strong>Edit 1</strong>
  I tried the following code suggested by baptiste but the letters seem to come through fine:</p>
  
  <pre><code>CairoPNG("test.png"); grid::grid.text("The disappearing J"); dev.off()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/JhksJ.png" alt="enter image description here"></p>
  
  <hr>
  
  <p><strong>Edit 2</strong></p>
  
  <p>Issue isolated courtesy of baptiste. It really doesn't seem to like rotating capital Js!</p>
  
  <pre><code>CairoPNG("c:\\temp\\test.png",width=60, height=300); grid::grid.text("Rejoicefully Juxtaposing Jelly with Jam\nabcdefghijklmnopqrstuvwxyz\nABCDEFGHIJKLMNOPQRSTUVWXYZ", rot=90); dev.off()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/WLHjj.png" alt="enter image description here"></p>