suggestion to address get_legend issue #205

DESCRIPTION

@@ -71,6 +71,6 @@ Collate:
     'stamp.R'
     'themes.R'
     'utils_ggplot2.R'
-RoxygenNote: 7.2.3
+RoxygenNote: 7.3.1
 Roxygen: list(markdown = TRUE)
 Encoding: UTF-8

NAMESPACE

@@ -46,6 +46,7 @@ export(gtable_squash_cols)
 export(gtable_squash_rows)
 export(insert_xaxis_grob)
 export(insert_yaxis_grob)
+export(is_zeroGrob)
 export(panel_border)
 export(pdf_null_device)
 export(plot_component_names)

R/get_legend.R

@@ -20,6 +20,6 @@
 #'                  plot_grid(NULL, legend, ncol=1),
 #'                  rel_widths=c(1, 0.2)))
 #' @export
-get_legend <- function(plot) {
-  get_plot_component(plot, "guide-box")
+get_legend <- function(plot, return_all = FALSE) {
+  get_plot_component(plot, "guide-box", return_all = return_all)
 }

R/get_plot_component.R

@@ -1,3 +1,15 @@
+#' is zero grob
+#'
+#' Function to check if a grob is a zero grob
+#'
+#' @param x A grob
+#' @return A logical value
+#' @export
+is_zeroGrob <- function(x) {
+  "zeroGrob" %in% attr(x, "class")
+}
+
+
 #' Get plot components
 #'
 #' Extract plot components from a ggplot or gtable. `get_plot_component()`
@@ -18,6 +30,9 @@
 #' p <- ggplot(mpg, aes(displ, cty)) + geom_point()
 #' ggdraw(get_plot_component(p, "ylab-l"))
 #'
+#' plot.mpg <- ggplot(mpg, aes(x = cty, y = hwy, colour = factor(cyl))) +  geom_point(size=2.5) + theme(legend.position='bottom')
+#' ggdraw(get_plot_component(plot.mpg, "guide-box"))
+#'
 #' @export
 get_plot_component <- function(plot, pattern, return_all = FALSE) {
   plot <- as_gtable(plot)
@@ -30,8 +45,16 @@ get_plot_component <- function(plot, pattern, return_all = FALSE) {
     if (length(grobIndex) > 1 && !return_all) {
       # If there's more than one grob, return just the first one
       warning("Multiple components found; returning the first one. To return all, use `return_all = TRUE`.")
-      grobIndex <- grobIndex[1]
-      matched_grobs <- grobs[[grobIndex]]
+      #grobIndex <- grobIndex[1]
+      matched_grobs1 <- grobs[grobIndex]
+      # Remove zero grobs
+      matched_grobs_non_zero <- matched_grobs1[!sapply(matched_grobs1, is_zeroGrob)]
+      # now get the first grob
+      if(length(matched_grobs_non_zero) == 0) {
+        matched_grobs <- NULL
+      } else {
+        matched_grobs <- matched_grobs_non_zero[[1]]
+      }
     } else if (length(grobIndex) > 1 && return_all) {
       # If there's more than one grob, return all as a list
       matched_grobs <- grobs[grobIndex]