R devel - Apr 2000 - x11 colortype problems ('gray' is broken?) (PR#512)

Hi,

  I occasionally run out of color in my X11 terminal.  At this
point, R will issue this error message:
        Error: X11 cannot allocate additional graphics colors.
Consider using colortype="pseudo.cube" or "gray".

An immediate x11(colortype="pseudo.cube") doesn't work as the
colortype seems to be shared among the different x11 plotting windows.
So I have to close all windows first, then I can open an x11 device
with the colortype "pseudo.cube".  (Neither the necessity to close all
windows nor the fact, that colortype is an option to X11 and not to
the plot command, is clear from the help pages or the error message.)

The real problem, however, comes with x11(colortype="gray") as this
brings up just a black screen (and it stays black).  I can't quite see
whether I'm stumbling across some issues with X resources, here.
x11() usually gives a white background.

Thanks,
  -tom


 --
platform = i586-unknown-linux
arch = i586
os = linux
system = i586, linux
status = 
major = 1
minor = 0.0
year = 2000
month = February
day = 29
language = R


-- 
mailto:tov@ece.cmu.edu (Tom Vogels)   Tel: (412) 268-6638   FAX: -3204


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On Fri, 7 Apr 2000 tov@ece.cmu.edu wrote:
> 
> Hi,
> 
>   I occasionally run out of color in my X11 terminal.  At this
> point, R will issue this error message:
>         Error: X11 cannot allocate additional graphics colors.
> Consider using colortype="pseudo.cube" or "gray".
> 
> An immediate x11(colortype="pseudo.cube") doesn't work as the
> colortype seems to be shared among the different x11 plotting windows.
> So I have to close all windows first, then I can open an x11 device
> with the colortype "pseudo.cube".  (Neither the necessity to
close all
> windows nor the fact, that colortype is an option to X11 and not to
> the plot command, is clear from the help pages or the error message.)
There is a single colortype shared by all x11 devices.  That couild eb
clearer!
> The real problem, however, comes with x11(colortype="gray") as
this
> brings up just a black screen (and it stays black).  I can't quite see
> whether I'm stumbling across some issues with X resources, here.
> x11() usually gives a white background.
No. It's a bug.  When you set x11(colortype="gray") it tries to
allocate
min(256, 2^depth) colours, that is all the colours on an 8-bit display.
That is clearly going to fail (unless perhaps your window manager is 
in mono).  So it does fail, set PaletteSize = 0, and then maps all
colours to black.  That's what the x11 driver seems to do when colour
allocation fails.  I suspect it should not open at all under those 
circumstances.

Quick fix:

static void SetupGrayScale()
{
    PaletteSize = 0;
    if (depth > 7)
	depth = 7;
    if (GetGrayPalette(display, colormap, 1 << depth) == 0)
	depth = 1;
}

(8 replaced by 7) in devX11.c.  I'll commit a more sophisticated one
to R-release.


-- 
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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