From 4a2d0865f816da069c49caffbdf643c3e32f2b3d Mon Sep 17 00:00:00 2001
From: Paul Murrell <paul@stat.auckland.ac.nz>
Date: Fri, 30 Aug 2024 16:26:31 +1200
Subject: [PATCH] handle empty input to xyPathToList() et al;  thanks to James
 Ward for th bug report

---
 DESCRIPTION  |  2 +-
 R/grob.R     |  8 ++++++++
 inst/NEWS.Rd |  7 +++++++
 tests/test.R | 12 ++++++++++++
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/DESCRIPTION b/DESCRIPTION
index 9332157..a7654c1 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: gridGeometry
 Type: Package
 Title: Polygon Geometry in 'grid'
-Version: 0.4-0
+Version: 0.4-1
 Authors@R: c(person("Paul", "Murrell", role = c("aut", "cre"),
                     email = "paul@stat.auckland.ac.nz"),
              person("Jack", "Wong", role = "aut"))
diff --git a/R/grob.R b/R/grob.R
index 486b47e..579f563 100644
--- a/R/grob.R
+++ b/R/grob.R
@@ -4,6 +4,10 @@
 
 ## Convert (closed) 'polyclip' polygon result to 'grid' path
 xyListPath <- function(x, rule, name=NULL, gp=gpar()) {
+    ## Handle empty 'x'
+    if (length(x) == 0) {
+        return(nullGrob(name=name))
+    }
     if (missing(rule)) {
         if (is.null(attr(x, "rule")))
             rule <- "winding"
@@ -28,6 +32,10 @@ xyListToPath <- xyListPath
 
 ## Convert (closed) 'polyclip' polygon result to 'grid' polygons
 xyListPolygon <- function(x, name=NULL, gp=gpar()) {
+    ## Handle empty 'x'
+    if (length(x) == 0) {
+        return(nullGrob(name=name))
+    }
     ## Remove any coordinate sets that are too short
     x <- x[sapply(x, function(c) length(c$x) > 1)]
     if (length(x) == 0) {
diff --git a/inst/NEWS.Rd b/inst/NEWS.Rd
index 50e68da..5442540 100755
--- a/inst/NEWS.Rd
+++ b/inst/NEWS.Rd
@@ -2,6 +2,13 @@
 \title{NEWS file for the gridGeometry package}
 \encoding{UTF-8}
 
+\section{Changes in version 0.4-1}{
+  \itemize{
+    \item Handle empty list or \code{NULL} input in
+    \code{xyListToPolygon()} and \code{xyListToPath()}.
+  }
+}
+
 \section{Changes in version 0.4-0}{
   \itemize{
     \item New functions \code{grid.polyoffset()} and
diff --git a/tests/test.R b/tests/test.R
index 0314306..996e3d4 100644
--- a/tests/test.R
+++ b/tests/test.R
@@ -217,3 +217,15 @@ gt <- gTree(children=gList(path, rect))
 grid.newpage()
 grid.reduce(gt, gp=gpar(fill="grey"))
 
+################################################################################
+## xyListTo*()
+
+## Check can handle empty list
+
+xyListToLine(NULL)
+xyListToPolygon(NULL)
+xyListToPath(NULL)
+
+xyListToLine(list())
+xyListToPolygon(list())
+xyListToPath(list())