[R] Determining physical display dimensions

[Marc Schwartz]

On Fri, 2005-08-19 at 13:17 -0500, Earl F. Glynn wrote: 
> "Berton Gunter" <gunter.berton at gene.com> wrote in message
> news:200508191747.j7JHlEBV017029 at faraday.gene.com...
> 
> > Failing that, (how) can this be done for Windows (XP or 2000, say) ?
> 
> Take a look at the Windows GetDeviceCaps API call
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/devcons_88s3.asp
> 
> Parameters that can be queried include:
> HORZRES  Width, in pixels, of the screen.
> VERTRES Height, in raster lines, of the screen.
> 
> HORZSIZE Width, in millimeters, of the physical screen
> VERTSIZE  Height, in millimeters, of the physical screen
> 
> The specifics of how to use this API call will vary by language.  Google
> will be your friend.


FWIW, in case anyone should see this thread and wonder how to do this
somewhat easily in R for systems running X, there is a CLI utility
called 'xdpyinfo' that returns a great deal of data on the connected
display(s).


> display.size <- system("xdpyinfo | grep dimensions", intern = TRUE)
> display.dpi <- system("xdpyinfo | grep resolution", intern = TRUE)

> display.size
[1] "  dimensions:    1600x1200 pixels (301x231 millimeters)"

> display.dpi
[1] "  resolution:    135x132 dots per inch"


One can then parse the above using R functions as required. Such as:

> d.size <- unlist(strsplit(display.size, split = "[[:space:]|(|)|x]"))

> d.size
[1] ""            ""            "dimensions:" ""
[5] ""            ""            "1600"        "1200"
[9] "pi"          "els"         ""            "301"
[13] "231"         "millimeters" 


> h.pix <- as.numeric(d.size[7])
> v.pix <- as.numeric(d.size[8])

> h.mm <- as.numeric(d.size[12])
> v.mm <- as.numeric(d.size[13])


> line1 <- sprintf("The current display is %d x %d pixels", 
                    h.pix, v.pix)


> line2 <- sprintf("with a physical size of %d x %d mm", h.mm, v.mm)


> cat(line1, line2, sep = "\n")
The current display is 1600 x 1200 pixels
with a physical size of 301 x 231 mm


This can get more complicated with multi-monitor systems, depending upon
whether you are running in xinerama (multi-monitor spanning mode) or
non-xinerama mode and consideration for symmetric or asymmetric
resolutions. 'man xdpyinfo' and 'man X' (noting the 'DISPLAY'
environment variable) will be helpful here to determine which
display/screen R is running on.

For example, on my system which has two displays, each with 1600x1200, I
get:

> Sys.getenv("DISPLAY")
DISPLAY
 ":0.0"

with R running on the main laptop LCD (15" diag), versus:

> Sys.getenv("DISPLAY")
DISPLAY
 ":0.1"

with R running on the external LCD (20.1" diag), with the DISPLAY
variable indicating:

":DisplayNumber.ScreenNumber"


Thus, on my system, the output of the system() calls are actually:

> display.size <- system("xdpyinfo | grep dimensions", intern = TRUE)
> display.dpi <- system("xdpyinfo | grep resolution", intern = TRUE)

> display.size
[1] "  dimensions:    1600x1200 pixels (301x231 millimeters)"
[2] "  dimensions:    1600x1200 pixels (411x311 millimeters)"

> display.dpi
[1] "  resolution:    135x132 dots per inch"
[2] "  resolution:    99x98 dots per inch"


HTH,

Marc Schwartz