Pass label to draw_key_text (#2458)

* Pass `label` to `draw_key_text`

To override the default "a" in the label of a text legend: first check if `data$label` has anything in it; if not, use "a" as before. However, if the user sets a label within `guide_legend(override.aes = list(label = "foo"))`, then use that label or vector of labels as the first arg of `textGrob`.

* Update NEWS.md

Added description for issue #2458

Author: brianwdavis

NEWS.md

@@ -101,6 +101,9 @@
 
 * The colorbar shows all colours of the scale (@has2k1, 2343).
 
+* Guides generated by `geom_text()` (e.g. colour) now accept custom labels using 
+  `guide_legend(override.aes = list(label = "foo"))` (@brianwdavis, #2458).
+
 ### Margins
 
 * Strips gain margins on all sides by default. This means that to fully justify

R/legend-draw.r

@@ -169,7 +169,9 @@ draw_key_smooth <- function(data, params, size) {
 #' @export
 #' @rdname draw_key
 draw_key_text <- function(data, params, size) {
-  textGrob("a", 0.5, 0.5,
+  if(is.null(data$label)) data$label <- "a"
+  
+  textGrob(data$label, 0.5, 0.5,
     rot = data$angle,
     gp = gpar(
       col = alpha(data$colour, data$alpha),