X11 Device Driver

[Prof Brian D Ripley]

On Fri, 2 Apr 1999, Ross Ihaka wrote:

> I have made some modifications to the X11 graphics driver so that it is
> more flexible about its use of colors.  I have added a new parameter to
> the X11/x11 function which controls this.  The parameter is currently
> called "colormodel" and works as follows:
> 
> 	colormodel = 0		Monochrome graphics
> 	colormodel = 1		Grayscale (256 shades)
> 	colormodel = 2		Pseudocolor1
> 	colormodel = 3		Pseudocolor2
> 	colormodel = 4		Truecolor
> 
> Pseudocolor1 allocates as big a color cube as possible and then
> approximates requested colors with colors from the cube.
> 
> Pseudocolor2 allocates colors "on-demand" until it runs out of
> colors.  You then get a "can't allocate colors" error message.
> 
> More sophisticated devices will support the color models of less
> sophisticated devices.  E.g. you can do grey-scale and pseudocolor
> on a truecolor device.
> 
> So, one question is:  How should this functionality be packaged?
> 
> One possibility is to have multiple X11 device driver entry points
> 
>     X11.mono, X11.gray, X11.pseudo1, X11.pseudo2, X11.color
> 
> This would be useful because people could use options() to set
> the appropriate default device.
> 
> Another possibility would be to have use an additional argument to
> the driver and to make it rather more meaningful than 0, 1, 2, 3, 4.

I would prefer a single driver, with (effectively)

X11(display = "", width = 7, height = 7, pointsize = 12, 
    colortype=options()$X11colortype)

and choosing type from "mono", "gray", "pseudo.cube", "pseudo", "true"
as appropriate.

> A second question is what should the default behavior be on Pseudocolor
> devices; Pseudocolor1 or Pseudocolor2?

Pseudocolor2, please.  I very rarely have a problem (but then I have
netscape and gs under control).

> Would anyone care to express an opinion.  I'd like to get this commited
> for the 0.64 release.

Yes, please.

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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