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#' Modify a ggplot or theme object by adding on new components.
#'
#' This operator allows you to add objects to a ggplot or theme object.
#'
#' If the first object is an object of class \code{ggplot}, you can add
#' the following types of objects, and it will return a modified ggplot
#' object.
#'
#' \itemize{
#' \item \code{data.frame}: replace current data.frame
#' (must use \code{\%+\%})
#' \item \code{uneval}: replace current aesthetics
#' \item \code{layer}: add new layer
#' \item \code{theme}: update plot theme
#' \item \code{scale}: replace current scale
#' \item \code{coord}: override current coordinate system
#' \item \code{facet}: override current coordinate faceting
#' }
#'
#' If the first object is an object of class \code{theme}, you can add
#' another theme object. This will return a modified theme object.
#'
#' For theme objects, the \code{+} operator and the \code{\%+replace\%}
#' can be used to modify elements in themes.
#'
#' The \code{+} operator completely replaces elements
#' with elements from e2.
#'
#' In contrast, the \code{\%+replace\%} operator does not replace the
#' entire element; it only updates element properties which are present
#' (not NULL) in the second object.
#'
#' @examples
#'
#' ### Adding objects to a ggplot object
#' p <- qplot(wt, mpg, colour = hp, data = mtcars)
#'
#' p + coord_cartesian(ylim = c(0, 40))
#' p + scale_colour_continuous(breaks = c(100, 300))
#' p + guides(colour = "colourbar")
#'
#' # Use a different data frame
#' m <- mtcars[1:10, ]
#' p %+% m
#'
#'
#' ### Adding objects to a theme object
#' # Compare these results of adding theme objects to other theme objects
#' add_el <- theme_grey() + theme(text = element_text(family = "Times"))
#' rep_el <- theme_grey() %+replace% theme(text = element_text(family = "Times"))
#'
#' add_el$text
#' rep_el$text
#'
#' @param e1 An object of class \code{ggplot} or \code{theme}
#' @param e2 A component to add to \code{e1}
#'
#' @export
#'
#' @seealso \code{\link{theme}}
#' @method + gg
#' @rdname gg-add
"+.gg" <- function(e1, e2) {
# Get the name of what was passed in as e2, and pass along so that it
# can be displayed in error messages
e2name <- deparse(substitute(e2))
if (is.theme(e1)) add_theme(e1, e2, e2name)
else if (is.ggplot(e1)) add_ggplot(e1, e2, e2name)
}
#' @rdname gg-add
#' @export
"%+%" <- `+.gg`
add_ggplot <- function(p, object, objectname) {
if (is.null(object)) return(p)
p <- plot_clone(p)
if (is.data.frame(object)) {
p$data <- object
} else if (is.theme(object)) {
p$theme <- update_theme(p$theme, object)
} else if (inherits(object, "scale")) {
p$scales$add(object)
} else if(inherits(object, "labels")) {
p <- update_labels(p, object)
} else if(inherits(object, "guides")) {
p <- update_guides(p, object)
} else if(inherits(object, "uneval")) {
p$mapping <- defaults(object, p$mapping)
labels <- lapply(object, deparse)
names(labels) <- names(object)
p <- update_labels(p, labels)
} else if (is.coord(object)) {
p$coordinates <- object
p
} else if (is.facet(object)) {
p$facet <- object
p
} else if(is.list(object)) {
for (o in object) {
p <- p + o
}
} else if(is.proto(object)) {
p <- switch(object$class(),
layer = {
p$layers <- append(p$layers, object)
# Add any new labels
mapping <- make_labels(object$mapping)
default <- make_labels(object$stat$default_aes())
new_labels <- defaults(mapping, default)
p$labels <- defaults(p$labels, new_labels)
p
},
coord = {
p$coordinates <- object
p
}
)
} else {
stop("Don't know how to add ", objectname, " to a plot",
call. = FALSE)
}
set_last_plot(p)
p
}
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