plot_layout_properties(): args layout accepts index (davidgohel#595)

Accept the layout index (see `layout_summary()`) as alternative to
the layout name (suggestion 2 in davidgohel#595).

NEWS.md

@@ -22,6 +22,7 @@ informative error message if the type is not present in layout (#601).
 - `plot_layout_properties()` plots more information by default now: layout name, ph label, ph id, ph type + index by default (#606).
 - `ph_location_type()`: new `type_idx` arg replaces the deprecated `id` arg (#606).
 - Add `ph_location_id()` as a new member to the `ph_location_*` family. It references a placeholder via its unique id (#606).
+- `plot_layout_properties()`: Accept the layout index (see `layout_summary()`) as alternative to the layout name (#595).
 
 ## Features
 

R/pptx_informations.R

@@ -118,7 +118,7 @@ layout_properties <- function(x, layout = NULL, master = NULL) {
 #'    _NB_: The id is set by PowerPoint automatically and lack a meaningful order.
 #'
 #' @param x an `rpptx` object
-#' @param layout slide layout name.
+#' @param layout slide layout name or numeric index (row index from [layout_summary()).
 #' @param master master layout name where `layout` is located.
 #' @param title if `TRUE` (default), adds a title with the layout name at the top.
 #' @param labels if `TRUE` (default), adds placeholder labels (centered in *red*).
@@ -129,19 +129,20 @@ layout_properties <- function(x, layout = NULL, master = NULL) {
 #' @param cex named list or vector to specify font size for `labels`, `type`, and `id`. Default is
 #'   `c(labels = .5, type = .5, id = .5)`. See [graphics::text()] for details on how `cex` works.
 #' @importFrom graphics plot rect text box
+#' @family functions for reading presentation information
 #' @examples
 #' x <- read_pptx()
 #' plot_layout_properties(x = x, layout = "Title Slide", master = "Office Theme")
-#' plot_layout_properties(x = x, layout = "Two Content")
+#' plot_layout_properties(x = x, layout = "Two Content") # no master needed for unique layout
+#' plot_layout_properties(x = x, layout = 4) # use layout index
 #' plot_layout_properties(x = x, layout = "Two Content", title = FALSE, type = FALSE, id = FALSE)
 #'
 #' # change font size
 #' plot_layout_properties(x = x, layout = "Two Content", cex = c(labels = 1, id = .7, type = .7))
 #'
-#' @family functions for reading presentation information
-#'
 plot_layout_properties <- function(x, layout = NULL, master = NULL, labels = TRUE, title = TRUE,
                                    type = TRUE, id = TRUE, cex = NULL) {
+  stop_if_not_rpptx(x, "x")
   old_par <- par(mar = c(2, 2, 1.5, 0))
   on.exit(par(old_par))
 
@@ -155,7 +156,8 @@ plot_layout_properties <- function(x, layout = NULL, master = NULL, labels = TRU
   }
   .cex <- utils::modifyList(x = cex_default, val = as.list(cex), keep.null = TRUE)
 
-  dat <- layout_properties(x, layout = layout, master = master)
+  la <- get_layout(x, layout, master)
+  dat <- layout_properties(x, layout = la$layout_name, master = la$master_name)
   if (length(unique(dat$name)) > 1) {
     cli::cli_abort(c("One single layout must be chosen",
       "x" = "Did you supply a master?"
@@ -183,7 +185,7 @@ plot_layout_properties <- function(x, layout = NULL, master = NULL, labels = TRU
   mtext("x [inch]", side = 1, line = 0, cex = 1.2, col = "darkgrey")
 
   if (title) {
-    title(main = paste("Layout:", layout))
+    title(main = paste("Layout:", la$layout_name))
   }
   if (labels) { # centered
     text(x = offx + cx / 2, y = -(offy + cy / 2), labels = dat$ph_label, cex = .cex$labels, col = "red", adj = c(.5, 1)) # adj-vert: avoid interference with type/id in small phs

tests/testthat/test-pptx-info.R

@@ -146,6 +146,26 @@ test_that("slide summary", {
 })
 
 
+
+test_that("plot layout properties: layout arg takes numeric index", {
+  x <- read_pptx()
+  las <- layout_summary(x)
+  ii <- as.numeric(rownames(las))
+
+  discarded_plot <- function(x, layout = NULL, master = NULL) { # avoid Rplots.pdf creation
+    file <- tempfile(fileext = ".png")
+    png(file, width = 7, height = 6, res = 150, units = "in")
+      plot_layout_properties(x, layout, master)
+    dev.off()
+  }
+
+  for (idx in ii) {
+    expect_no_error(discarded_plot(x, idx))
+  }
+  expect_no_error(discarded_plot(x, 1, "Office Theme"))
+})
+
+
 test_that("color scheme", {
   x <- read_pptx()
   cs <- color_scheme(x)