Only merge legends if title and labels are the same

Author: hadley

NEWS

@@ -32,4 +32,6 @@ ggplot2 0.8.5 (2009-XX-XX) ----------------------------------------
 * scale_shape_discrete and scale_size_continuous added to scales to match 
   naming convention of all other scales (Fixes #47)
 * scale_colour_gradient, scale_colour_gradient2 & scale_colour_gradientn now
-  have formatter argument to match scale_continuous
+  have formatter argument to match scale_continuous
+* legends will only merge if both the title and all labels are the same.
+  (Fixes #16)

R/guides-legend.r

@@ -64,12 +64,14 @@ guide_legends <- function(scales, layers, default_mapping, theme) {
   legend <- scales$legend_desc(theme)
   if (length(legend$titles) == 0) return()
 
-  titles <- unique(legend$titles)
-  lapply(titles, function(title) {
-    keys <- legend$keys[sapply(legend$titles, identical, title)]
+  hashes <- unique(legend$hash)
+  lapply(hashes, function(hash) {
+    keys <- legend$keys[legend$hash == hash]
+    title <- legend$title[legend$hash == hash][[1]]
+    
     if (length(keys) > 1) { 
       # Multiple scales for this legend      
-      keys <- merge_recurse(keys, by = c(".value", ".label"))
+      keys <- merge_recurse(keys, by = ".label")
     } else {
       keys <- keys[[1]]
     }

R/scales-.r

@@ -56,6 +56,7 @@ Scales <- proto(Scale, expr={
   legend_desc <- function(., theme) {
     # Loop through all scales, creating a list of titles, and a list of keys
     keys <- titles <- vector("list", .$n())
+    hash <- character(.$n())
 
     for(i in seq_len(.$n())) {
       scale <- .$.scales[[i]]
@@ -70,15 +71,16 @@ Scales <- proto(Scale, expr={
       }
 
       key <- data.frame(
-        scale$output_breaks(), scale$input_breaks(), I(scale$labels()))
-      names(key) <- c(output, ".value", ".label")
+        scale$output_breaks(), I(scale$labels()))
+      names(key) <- c(output, ".label")
 
       keys[[i]] <- key
+      hash[i] <- digest(list(titles[[i]], key$.label))
     }
 
     empty <- sapply(titles, is.null)
 
-    list(titles = titles[!empty], keys = keys[!empty])
+    list(titles = titles[!empty], keys = keys[!empty], hash = hash[!empty])
 
   }