Default R Font Changed After Upgrade to Debian 8

Good day,

The code is :

png("grainy.png", h = 600, w = 900)
plot(1:10, main = "abcedfghijklmnopqrstuvwxyz", cex.main = 4, cex.lab = 4,
cex.axis = 4) dev.off()

and the server has the characteristics :

getOption("bitmapType")

[1] "cairo"

sessionInfo()

R version 3.2.3 (2015-12-10)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux 8 (jessie)

locale:
 [1] LC_CTYPE=C.UTF-8       LC_NUMERIC=C           LC_TIME=C.UTF-8
 [4] LC_COLLATE=C.UTF-8     LC_MONETARY=C.UTF-8    LC_MESSAGES=C.UTF-8
 [7] LC_PAPER=C.UTF-8       LC_NAME=C              LC_ADDRESS=C
[10] LC_TELEPHONE=C         LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

capabilities()

       jpeg         png        tiff       tcltk         X11        aqua
       TRUE        TRUE        TRUE        TRUE        TRUE       FALSE
   http/ftp     sockets      libxml        fifo      cledit       iconv
       TRUE        TRUE        TRUE        TRUE        TRUE        TRUE
        NLS     profmem       cairo         ICU long.double     libcurl
       TRUE       FALSE        TRUE        TRUE        TRUE        TRUE

~$ dpkg -l | grep cairo
ii  libcairo-gobject2:amd64                                     1.14.0-2.1  
                           amd64        Cairo 2D vector graphics library
(GObject library) ii  libcairo-perl                                        
      1.104-2                                 amd64        Perl interface
to the Cairo graphics library ii  libcairo-script-interpreter2:amd64       
                  1.14.0-2.1                              amd64       
Cairo 2D vector graphics library (script interpreter) ii  libcairo2:amd64  
                                          1.14.0-2.1                       
      amd64        Cairo 2D vector graphics library ii  libcairo2-dev      
                                        1.14.0-2.1                         
    amd64        Development files for the Cairo 2D graphics library ii 
libmono-cairo2.0-cil                                        3.2.8+dfsg-10  
                        all          Mono Cairo library (for CLI 2.0) ii 
libmono-cairo4.0-cil                                        3.2.8+dfsg-10  
                        all          Mono Cairo library (for CLI 4.0) ii 
libpangocairo-1.0-0:amd64                                   1.36.8-3       
                        amd64        Layout and rendering of
internationalized text ii  libpixman-1-0:amd64                             
           0.32.6-3                                amd64       
pixel-manipulation library for X and cairo ii  libpixman-1-dev             
                               0.32.6-3                               
amd64        pixel-manipulation library for X and cairo (development files)
ii  python-cairo                                                1.8.8-1+b2 
                            amd64        Python bindings for the Cairo
vector graphics library ii  python-gi-cairo                                
            3.14.0-1                                amd64        Python
Cairo bindings for the GObject library ii  python3-cairo                   
                           1.10.0+dfsg-4+b1                        amd64   
    Python 3 bindings for the Cairo vector graphics library ii 
python3-gi-cairo                                            3.14.0-1       
                        amd64        Python 3 Cairo bindings for the
GObject library

I recently noticed it also affects other software, like Firefox internet
browser.

--------------------------------------
Dario Strbenac
PhD Student
University of Sydney
Camperdown NSW 2050
Australia