R devel - Nov 2000 - RE: [R] Graphics-Device-Size vs. Window-Size

Hi Paul,

thank you for responding. I indeed overlooked, that units="inch" gives
stable results, independent of resizing the graphics window on the screen.
And indeed I would find some way fiddling around to get my graphic done.

However I see a general problem here and I would like a general solution:
Obviously we are dealing with two coordinate systems: the graphics device
size (call it representation layer) and the window size on the screen (call
it presentation layer). If I do any graphics programming, I do not want to
depend on arbitrary window sizes. It is nice to know my device has 8 inches
and that text x needs y inches in width. But the adress space in which
plotting is done are the "user" coordinates. So, for the simplest
example,
specifying xlim=c(0,1) generates a stable reference WHICH DOES NOT CHANGE ON
RESIZING THE GRAPHICS WINDOW. As strwidth(units="user") DOES CHANGE ON
RESIZING THE GRAPHICS WINDOW the units arguably ARE NOT the user
coordinates.

I tend to believe this is a BUG. Same for units="figure".

I also tend to believe, that resizing a graphics window should rescale the
font size used ON SCREEN, because currently we have the following mixup of
representation layer and presentation layer: if a certain text in cex=1
fills 50% width of my user coordinates on the device, and I decrease window
size, with stable screen font size the same text now fills more than 50%
width. This 'more' is reflected in strwidth(units='user'), but
as said
before, the units strwidth(units='user') gives are not user but
user*(device/window). So if a special strwidth measure is needed which
refers to the presentation layer it should be named accordingly. Those
units='user' and units='figure' should return stable measures
refering to
the representation layer.

Regards


Jens

> version
         _
platform Windows
arch     x86
os       Win32
system   x86, Win32
status
major    1
minor    1.1
year     2000
month    August
day      15
language R


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To:
r-devel-request@stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

Hi

[This also a reply to "[Rd] Another inconsistency concerning device-size
vs.
window-size"]

I will try to give a brief overview of the way R graphics devices
(conceptually at least) work (to me at least).

Yes a window (x11 or win32) is a device.  Other devices are:  postscript,
png, jpeg, pictex, bmp.  Windows are different to these other devices
because they can be interactively resized.  R treats a change in window size
as a change in the (absolute) physical size of the device.  Perhaps another
way to respond to a window resize would be to retain the same physical
device size and have scroll bars on the window, but I don't think this is
still what you would want (?)

Text size is most often specified (ultmately) as a physical (absolute)
pointsize.  The reason for this (I think) is that ultimately text has to be
big enough to read.  Thus strwidth() will return the same answer in any
absolute set of units (e.g., "inch").  The correct interpretation of
strwidth(mytext, "user") is that it is the physical size of the text
_converted_ into user coordinates.

Automatic resizing of text is a tricky issue.  The text size is
automatically resized by R in some cases (e.g., for multiple figures), but
scaling text size continuously (e.g., with window size) does not tend to
produce useful results (e.g., it is too easy to produce text which is too
small to read).

I suspect that I'm not providing you with the answer you want;  I guess
I'm
trying to explain how R works so that you can do what you need to.  Perhaps
it would help me to help you more if you described the graphics task you are
trying to achieve (?).

With respect to the par("din") inconsistency, that _is_ undesirable
behaviour.  The correct behaviour is the second one.  Could you please
submit a bug report for this (including your example).

Thanks

Paul


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To:
r-devel-request@stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._