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strange interaction of quartz() with videoprojector

4 messages · Brian Ripley, Ken Knoblauch, Simon Urbanek

Original
Ken Knoblauch
# 
Hi,

The new graphics window defaults in R 2.7.0 are great but I've
noticed a strange phenomenon when I'm using R with my MacBook Pro
connected to a videoprojector.  Under these conditions,
the quartz window that is opened is tiny,
about 1/5 the default size and the line colors are a light
grey (or a light color, at least.  Not 100% sure that it is grey).
As soon as I detach the videoprojector and reset the
display size, everything returns to normal.

The minimal example would be to hook up your portable to
a videoprojector, start R and run

quartz()

Does anyone else see this?

I can get the normal default with

quartz(width = 30, height = 30)

but the text and points are very small.  I can get around this
with cex and col arguments but this is not optimal.  Not great
for teaching.

Thank you for any suggestions.  SessionInfo below.

Ken



R version 2.7.0 Patched (2008-04-30 r45572)
i386-apple-darwin8.10.1

locale:
en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base
Brian Ripley
# 
You can set the quartz() argument 'dpi'.  I'm not sure why this is being 
detected wrongly, but it looks as if it is.
On Mon, 5 May 2008, Kenneth Knoblauch wrote:

            

      
      
      
    

        
This could be the effect of antialiasing on narrow lines.

            

      
      
      
    

        

      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Ken Knoblauch
    

    

      
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A setting of dpi = 1.5 * 72 generates about the right size
graphics and alleviates the light lines problem, which must
have been from the antialiasing, as you proposed.

This seems to be related to the automatic selection of resolution
in System Preferences for Displays.  The values chosen automatically
which generated the small quartz windows are set at
1280 x 1024.  At one point, restarting the machine while
connected to the videoprojector, it started up with a lower
resolution and the quartz window worked fine.  I wasn't
able to reproduce this though by manually reducing the
resolution in the preferences.  I have to experiment
a bit more to see how to get it to start up automatically
in the lower resolution, which would seem to obviate the problem
for the short term.

Thank you for your suggestions.

Ken


Quoting Prof Brian Ripley <ripley at stats.ox.ac.uk>:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Simon Urbanek
    

    

      
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On May 5, 2008, at 4:36 AM, Kenneth Knoblauch wrote:

        

            

      
      
      
    

        
1.5*72 is ca. 100 dpi which most displays use. Clearly on a projector  
DPI is not very meaningful since it varies with the projected distance.

            

      
      
      
    

        
FWIW in most cases what you call "automatic" is not very helpful.  
Fortunately the Display settings are smart and will remember the last  
used modes, so if you set up the correct resolution, it will be  
remembered and you can restore it with one click. In most cases I  
recommend using projector's native resolution as it is the only  
resolution that is faithfully represented.

(This is not really Quartz-related, it hold true for any projection  
with the possible exception of video projection).

Cheers,
Simon