For the example you give, grid.path() diverts to drawing a polygon
(because there is no 'id' specified), and the NAs in 'x' generate two
separate polygons, which get drawn one on top of the other.
The correct analogy to the polypath() example is ...
x2 <- matrix(x[!is.na(x)], ncol=2)
grid.path(x2[,1], x2[,2], id=rep(1:2, each=4),
rule="winding", gp=gpar(="#BEBEBE80"))
... which produces the same (wrong) result as polypath() on Windows.
Also, the grid.path() result for your example is NOT the same as the
correct result; we do NOT want a separate shade for the intersecting
region when the "winding" fill rule is working correctly. The fill
should be the same across the union of the square regions (this is what
Cairo and PDF on Linux produce).
Another data point: the problem is NOT just a matter of getting the
rules round the wrong way in the devWindows.c; using rule="evenodd"
produces the SAME result as using rule="winding".
One more data point: this is not JUST a problem with polypath().
Creating a self-intersecting polygon and then drawing it, using
polygon(), in windows(fillEvenOdd=FALSE) and windows(filleEvenOdd=TRUE)
produces exactly the same result.
Sadly, none of that helps to explain why the "winding" rule is not
working on Windows :(
Thanks for reporting the problem - needs more study to find out what is
going wrong.
Paul
On 03/08/16 18:47, Michael Sumner wrote:
Hello,
it's probably worth adding that this is not a problem with pathGrob, only
polypath.
This code is sufficient to demonstrate the problem in Windows.
## overlapping, both clock-wise
x <- cbind(c(.1, .1, .6, .6, NA, .4, .4, .9, .9),
c(.1, .6, .6, .1, NA, .4, .9, .9, .4))
## only a problem on Windows windows() and png()
plot(x);polypath(x, rule = "winding", col = "#BEBEBE80")
This code shows the same behaviour on different systems/devices.
## no problem on Windows/Linux/PNG/PDF ...
library(grid)
grid.newpage()
pushViewport(viewport(0.5, 0.5, width = 1, height = 1))
grid.draw(pathGrob(x[,1], x[,2], rule = "winding", gp = gpar(fill =
"#BEBEBE80")))
Cheers, Mike.
On Wed, 3 Aug 2016 at 16:24 Michael Sumner <mdsumner at gmail.com> wrote:
Hi, I see different results in png() and pdf() for polypath() on Windows
when using the "winding" rule
## overlapping, both clock-wise
x <- cbind(c(.1, .1, .6, .6, NA, .4, .4, .9, .9),
c(.1, .6, .6, .1, NA, .4, .9, .9, .4))
pfun <- function() {
plot(x)
polypath(x * 0.8 + 0.2, rule = "winding", col = "#BEBEBE80")
polypath(x, rule = "winding", col = "#BEBEBE80")
}
## output "windows.png/pdf" or "unix.png/pdf"
label <- .Platform$OS.type
png(sprintf("%s.png", label))
pfun()
dev.off()
pdf(sprintf("%s.pdf", label))
pfun()
dev.off()
Visually, the result in the "windows.png" file is as if the "evenodd"
was specified. All other examples unix.pdf, unix.png, windows.pdf give
the expected result - which is "all bounded regions shaded grey, with
tones for the different regions of overlap". The unexpected result is
completely transparent region.
Is this a known/expected difference on Windows? I see the unexpected
result in 3.3.1 and in R version 3.3.1 Patched (2016-07-27 r70991) on
Windows.
Cheers, Mike.
--
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia
--
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia
[[alternative HTML version deleted]]