Ensure labels work in all continuous colour gradients

NEWS

@@ -1,27 +1,35 @@
-ggplot2 0.8.4  (2009-XX-XX)
-----------------------------------------
+ggplot2 0.8.4 (2009-XX-XX) ----------------------------------------
 
 * aes and aes_string both convert prefixes to full names
-* aesthetics: corrected list of aesthetics to include american spelling of colour as well as base R abbreviations
+* aesthetics: corrected list of aesthetics to include american spelling of
+  colour as well as base R abbreviations
 * aesthetics: fix bug in detecting which aesthetics are calculated
 * aes_string treats NULL as "NULL"
 * annotate now works with missing x and y (e.g. for geom_rect)
 * continuous scale limits now automatically sorted
 * coord_polar: fix bug if breaks not all inside limits
 * facet_wrap: can now specify both ncol and nrow without getting an error
-* facet_wrap: now works with statistics that produce both x and y values (e.g. stat_qq)
-* fullseq now adds additional break on bottom if necessary, so that the include.lowest argument in cut never comes into play (this the source of a potential bug in histograms)
+* facet_wrap: now works with statistics that produce both x and y values (e.g.
+  stat_qq)
+* fullseq now adds additional break on bottom if necessary, so that the
+  include.lowest argument in cut never comes into play (this the source of a
+  potential bug in histograms)
 * geom_boxplot: alpha now affects fill colour of boxes only
-* geom_path correctly switches to segments if varying alpha used (thanks to  Karl Ove Hufthammer for the report and Baptiste Auguie for the fix)
+* geom_path correctly switches to segments if varying alpha used (thanks to
+  Karl Ove Hufthammer for the report and Baptiste Auguie for the fix)
 * geom_point: the alpha aesthetic now also affects the fill.
-* geom_ribbon always sorts input to avoid problems with certain pathological inputs
+* geom_ribbon always sorts input to avoid problems with certain pathological
+  inputs
 * geom_smooth was incorrectly applying alpha to line colour in the legend
 * nullGrob renamed to zeroGrob to avoid name conflict with grid
 * position_collide now works with missing values
 * position_stack: fixed bug in detection of overlap for negative values
-* scale_discrete_position now uses drop argument to force dropping of unused levels
-* scale_gradient now uses labels parameters, if supplied
+* scale_discrete_position now uses drop argument to force dropping of unused
+  levels
+* scale_gradient, scale_gradient2 and scale_gradientn now uses label
+  parameters, if supplied
 * scale_x_inverse, scale_y_inverse now actually work, and added recip as alias
 * stat_qq now correctly groups results
-* stat_smooth will not try and fit a line to 2 or fewer points (previously didn't try for only 1 point)
+* stat_smooth will not try and fit a line to 2 or fewer points (previously
+  didn't try for only 1 point)
 * stat_spoke now works with reversed scales

R/scale-continuous-colour.r

@@ -117,7 +117,9 @@ ScaleGradient2 <- proto(ScaleContinuous, expr={
   desc <- "Smooth gradient between three colours (high, low and midpoints)"
 
   output_breaks <- function(.) .$map(.$input_breaks())
-  labels <- function(.) .$.tr$label(.$input_breaks())
+  labels <- function(.) {
+    nulldefault(.$.labels, .$.tr$label(.$input_breaks()))
+  }
 
   icon <- function(.) {
     g <- scale_fill_gradient2()
@@ -215,7 +217,9 @@ ScaleGradientn <- proto(ScaleContinuous, expr={
   desc <- "Smooth gradient between n colours"
 
   output_breaks <- function(.) .$map(.$input_breaks())
-  labels <- function(.) .$.tr$label(.$input_breaks())
+  labels <- function(.) {
+    nulldefault(.$.labels, .$.tr$label(.$input_breaks()))
+  }
 
   icon <- function(.) {
     g <- scale_fill_gradientn(colours = rainbow(7))
@@ -242,6 +246,10 @@ ScaleGradientn <- proto(ScaleContinuous, expr={
     (d <- qplot(x, y, data=dsub, colour=diff))
 
     d + scale_colour_gradientn(colour = rainbow(7))
+    breaks <- c(-0.5, 0, 0.5)
+    d + scale_colour_gradientn(colour = rainbow(7), 
+      breaks = breaks, labels = format(breaks))
+
     d + scale_colour_gradientn(colour = topo.colors(10))
     d + scale_colour_gradientn(colour = terrain.colors(10))