Add files in order of trailing numeric index (davidgohel#596)

In class `dir_collection`, files are added to a container during
initialization using alphabetical sorting. This caused the slide
layout order to deviate from the one in the PPTX file, for example,
when calling layout_summary(). Files are now added to a container
in the order of their trailing numeric index. For example,
`slideLayout2.xml` will now preceed `slideLayout10.xml`. Before,
alphabetical sorting was used, where `slideLayout10.xml` comes before `slideLayout2.xml`.

DESCRIPTION

@@ -1,7 +1,7 @@
 Type: Package
 Package: officer
 Title: Manipulation of Microsoft Word and PowerPoint Documents
-Version: 0.6.7.007
+Version: 0.6.7.008
 Authors@R: c(
     person("David", "Gohel", , "[email protected]", role = c("aut", "cre")),
     person("Stefan", "Moog", , "[email protected]", role = "aut"),

NEWS.md

@@ -7,6 +7,8 @@
 - complete the manual of `body_add_docx()` with a note about the file basename
 that can not contain ' ' and trigger an error if it contains a ' '. 
 - `plot_layout_properties()` gains a 'title' parameter, which will add the layout name as the plot title. Defaults to `FALSE`, to not alter the old behavior. Also, the slide width and height are now correctly displayed in the plot. Before, a box was drawn around the plot area. However, the plot area var with device size, not slide size.
+- class `dir_collection`: Files are now added to a container in the order of their trailing numeric index (#596).
+For example, `slideLayout2.xml` will now preceed `slideLayout10.xml`. Before, alphabetical sorting was used, where `slideLayout10.xml` comes before `slideLayout2.xml`.
 
 ## Features
 

R/ppt_class_dir_collection.R

@@ -1,3 +1,31 @@
+# Extract trailing numeric index in .xml filename
+#
+# Useful to for slideMaster and slideLayout .xml files.
+#
+# Examples:
+#   files <- c("slideLayout1.xml", "slideLayout2.xml", "slideLayout10.xml")
+#   get_file_index(files)
+#
+get_file_index <- function(file) {
+  sub(pattern = ".+?(\\d+).xml$", replacement = "\\1", x = basename(file), ignore.case = TRUE) |> as.numeric()
+}
+
+
+# Sort xml filenames by trailing numeric index
+#
+# Useful to for slideMaster and slideLayout xml files.
+#
+# Examples:
+#   files <- c("slideLayout1.xml", "slideLayout2.xml", "slideLayout12.xml")
+#   sort_by_index(files)  # => order corresponding to trailing index
+#   sort(files)           # => incorrect lexicographical ordering
+#
+sort_by_index <- function(x) {
+  indexes <- get_file_index(x)  # only
+  x[order(indexes)]
+}
+
+
 # dir_collection ---------------------------------------------------------
 dir_collection <- R6Class(
   "dir_collection",
@@ -6,8 +34,8 @@ dir_collection <- R6Class(
     initialize = function( package_dir, container ) {
       dir_ <- file.path(package_dir, container$dir_name())
       private$package_dir <- package_dir
-
       filenames <- list.files(path = dir_, pattern = "\\.xml$", full.names = TRUE)
+      filenames <- sort_by_index(filenames)  # see issue 596
       private$collection <- lapply( filenames, function(x, container){
         container$clone()$feed(x)
       }, container = container)