layout_summary() layout order deviates from layout order in PPTX file

[markheckmann]

The order of the layouts in layout_summary() may deviate from the layout order in the PPTX master.

As this may irritate the user (in this case me :D), I suggest to return a layout order that matches the one in the PPTX file.

Example

File: many_layouts.pptx => This is the internal template.pptx with 4 new layouts (layout_8 to layout_11) added at the end.

url <- "https://github.com/user-attachments/files/16825504/many_layouts.pptx"
file <- tempfile(fileext = ".pptx")
download.file(url, file)
x <- read_pptx(file)
x$slideLayouts$get_metadata()

NB: I used x$slideLayouts$get_metadata() as layout_summary() calls this function internally.

        master_file              name          filename master_name
1  slideMaster1.xml       Title Slide  slideLayout1.xml    Master_1
2  slideMaster1.xml         layout_10 slideLayout10.xml    Master_1
3  slideMaster1.xml         layout_11 slideLayout11.xml    Master_1
4  slideMaster1.xml Title and Content  slideLayout2.xml    Master_1
5  slideMaster1.xml    Section Header  slideLayout3.xml    Master_1
6  slideMaster1.xml       Two Content  slideLayout4.xml    Master_1
7  slideMaster1.xml        Comparison  slideLayout5.xml    Master_1
8  slideMaster1.xml        Title Only  slideLayout6.xml    Master_1
9  slideMaster1.xml             Blank  slideLayout7.xml    Master_1
10 slideMaster1.xml          layout_8  slideLayout8.xml    Master_1
11 slideMaster1.xml          layout_9  slideLayout9.xml    Master_1

layout_10 and layout_11 should appear at the end, like in the PPTX file. However, the ordering in x$slideLayouts$get_metadata() appears to be lexicographical over filename. Hence, 10 and 11 come before 2, yielding a layout order that deviates from the PPTX file.

Analysis

The reason for this lies in the way how the file names are read during initialization in class dir_collection (see line 10 in file ppt_class_dir_collection.R.

...
filenames <- list.files(path = dir_, pattern = "\\.xml$", full.names = TRUE)
...

As per the docs, list.files will apply an alphabetic sort here:

The files are sorted in alphabetical order, on the full path if full.names = TRUE.

[markheckmann]

@davidgohel I changed the order in which files are added to the container in this branch in this file.

The layout order comes out as expected now:

url <- "https://github.com/user-attachments/files/16825504/many_layouts.pptx"
file <- tempfile(fileext = ".pptx")
download.file(url, file)
x <- read_pptx(file)
layout_summary(x) 

              layout   master
1        Title Slide Master_1
2  Title and Content Master_1
3     Section Header Master_1
4        Two Content Master_1
5         Comparison Master_1
6         Title Only Master_1
7              Blank Master_1
8           layout_8 Master_1
9           layout_9 Master_1
10         layout_10 Master_1
11         layout_11 Master_1

All tests are still passed. However, this is a change in a central class. So I would like to make sure, that there are no unwanted side effects.

An alternative to this approach would be to do the reordering directly in get_metadata() and other places where this may be relevant.

@davidgohel What do you think?

[davidgohel]

@markheckmann I think you are focused and accurate on these aspects.

For professional reasons, I don't have the ability to focus on the subject these days (things should be better after September/October). So if you feel able to PR, again it will be welcome.

If something break, I think the coverage test will show it (and if not, well I'll take time to fix what need to be fixed)

[markheckmann]

okay, great. PR is ready