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plot-render.r
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#' Build a plot with all the usual bits and pieces.
#'
#' This function builds all grobs necessary for displaying the plot, and
#' stores them in a special data structure called a \code{\link{gtable}}.
#' This object is amenable to programmatic manipulation, should you want
#' to (e.g.) make the legend box 2 cm wide, or combine multiple plots into
#' a single display, preserving aspect ratios across the plots.
#'
#' @seealso \code{\link{print.ggplot}} and \code{link{benchplot}} for
#' for functions that contain the complete set of steps for generating
#' a ggplot2 plot.
#' @return a \code{\link{gtable}} object
#' @keywords internal
#' @param plot plot object
#' @param data plot data generated by \code{\link{ggplot_build}}
#' @export
ggplot_gtable <- function(data) {
plot <- data$plot
panel <- data$panel
data <- data$data
theme <- plot_theme(plot)
build_grob <- function(layer, layer_data) {
if (nrow(layer_data) == 0) return()
dlply(layer_data, "PANEL", function(df) {
panel_i <- match(df$PANEL[1], panel$layout$PANEL)
layer$make_grob(df, scales = panel$ranges[[panel_i]], cs = plot$coord)
}, .drop = FALSE)
}
# helper function return the position of panels in plot_table
find_panel <- function(table) {
layout <- table$layout
panels <- layout[grepl("^panel", layout$name), , drop = FALSE]
data.frame(
t = min(panels$t),
r = max(panels$r),
b = max(panels$b),
l = min(panels$l)
)
}
# List by layer, list by panel
geom_grobs <- Map(build_grob, plot$layer, data)
plot_table <- facet_render(plot$facet, panel, plot$coordinates,
plot_theme(plot), geom_grobs)
# Axis labels
labels <- coord_labels(plot$coordinates, list(
x = xlabel(panel, plot$labels),
y = ylabel(panel, plot$labels)
))
xlabel <- element_render(theme, "axis.title.x", labels$x)
ylabel <- element_render(theme, "axis.title.y", labels$y)
panel_dim <- find_panel(plot_table)
xlab_height <- grobHeight(xlabel) +
if (is.null(labels$x)) unit(0, "lines") else unit(0.5, "lines")
plot_table <- gtable_add_rows(plot_table, xlab_height)
plot_table <- gtable_add_grob(plot_table, xlabel, name = "xlab",
l = panel_dim$l, r = panel_dim$r, t = -1, clip = "off")
ylab_width <- grobWidth(ylabel) +
if (is.null(labels$y)) unit(0, "lines") else unit(0.5, "lines")
plot_table <- gtable_add_cols(plot_table, ylab_width, pos = 0)
plot_table <- gtable_add_grob(plot_table, ylabel, name = "ylab",
l = 1, b = panel_dim$b, t = panel_dim$t, clip = "off")
# Legends
position <- theme$legend.position
if (length(position) == 2) {
coords <- position
position <- "manual"
}
legend_box <- if (position != "none") {
build_guides(plot$scales, plot$layers, plot$mapping, position, theme, plot$guides, plot$labels)
} else {
zeroGrob()
}
if (is.zero(legend_box)) {
position <- "none"
} else {
# these are a bad hack, since it modifies the contents fo viewpoint directly...
legend_width <- gtable_width(legend_box) + theme$legend.margin
legend_height <- gtable_height(legend_box) + theme$legend.margin
# Set the justification of the legend box
# First value is xjust, second value is yjust
just <- valid.just(theme$legend.justification)
xjust <- just[1]
yjust <- just[2]
if (position == "manual") {
xpos <- theme$legend.position[1]
ypos <- theme$legend.position[2]
# x and y are specified via theme$legend.position (i.e., coords)
legend_box <- editGrob(legend_box,
vp = viewport(x = xpos, y = ypos, just = c(xjust, yjust),
height = legend_height, width = legend_width))
} else {
# x and y are adjusted using justification of legend box (i.e., theme$legend.justification)
legend_box <- editGrob(legend_box,
vp = viewport(x = xjust, y = yjust, just = c(xjust, yjust)))
}
}
panel_dim <- find_panel(plot_table)
# for align-to-device, use this:
# panel_dim <- summarise(plot_table$layout, t = min(t), r = max(r), b = max(b), l = min(l))
if (position == "left") {
plot_table <- gtable_add_cols(plot_table, legend_width, pos = 0)
plot_table <- gtable_add_grob(plot_table, legend_box, clip = "off",
t = panel_dim$t, b = panel_dim$b, l = 1, r = 1, name = "guide-box")
} else if (position == "right") {
plot_table <- gtable_add_cols(plot_table, legend_width, pos = -1)
plot_table <- gtable_add_grob(plot_table, legend_box, clip = "off",
t = panel_dim$t, b = panel_dim$b, l = -1, r = -1, name = "guide-box")
} else if (position == "bottom") {
plot_table <- gtable_add_rows(plot_table, legend_height, pos = -1)
plot_table <- gtable_add_grob(plot_table, legend_box, clip = "off",
t = -1, b = -1, l = panel_dim$l, r = panel_dim$r, name = "guide-box")
} else if (position == "top") {
plot_table <- gtable_add_rows(plot_table, legend_height, pos = 0)
plot_table <- gtable_add_grob(plot_table, legend_box, clip = "off",
t = 1, b = 1, l = panel_dim$l, r = panel_dim$r, name = "guide-box")
} else if (position == "manual") {
# should guide box expand whole region or region withoug margin?
plot_table <- gtable_add_grob(plot_table, legend_box,
t = panel_dim$t, b = panel_dim$b, l = panel_dim$l, r = panel_dim$r,
clip = "off", name = "guide-box")
}
# Title
title <- element_render(theme, "plot.title", plot$labels$title)
title_height <- grobHeight(title) +
if (is.null(plot$labels$title)) unit(0, "lines") else unit(0.5, "lines")
pans <- plot_table$layout[grepl("^panel", plot_table$layout$name), ,
drop = FALSE]
plot_table <- gtable_add_rows(plot_table, title_height, pos = 0)
plot_table <- gtable_add_grob(plot_table, title, name = "title",
t = 1, b = 1, l = min(pans$l), r = max(pans$r), clip = "off")
# Margins
plot_table <- gtable_add_rows(plot_table, theme$plot.margin[1], pos = 0)
plot_table <- gtable_add_cols(plot_table, theme$plot.margin[2])
plot_table <- gtable_add_rows(plot_table, theme$plot.margin[3])
plot_table <- gtable_add_cols(plot_table, theme$plot.margin[4], pos = 0)
if (inherits(theme$plot.background, "element")) {
plot_table <- gtable_add_grob(plot_table,
element_render(theme, "plot.background"),
t = 1, l = 1, b = -1, r = -1, name = "background", z = -Inf)
plot_table$layout <- plot_table$layout[c(nrow(plot_table$layout), 1:(nrow(plot_table$layout) - 1)),]
plot_table$grobs <- plot_table$grobs[c(nrow(plot_table$layout), 1:(nrow(plot_table$layout) - 1))]
}
plot_table
}
#' Draw plot on current graphics device.
#'
#' @param x plot to display
#' @param newpage draw new (empty) page first?
#' @param vp viewport to draw plot in
#' @param ... other arguments not used by this method
#' @keywords hplot
#' @export
#' @method print ggplot
print.ggplot <- function(x, newpage = is.null(vp), vp = NULL, ...) {
set_last_plot(x)
if (newpage) grid.newpage()
data <- ggplot_build(x)
gtable <- ggplot_gtable(data)
if (is.null(vp)) {
grid.draw(gtable)
} else {
if (is.character(vp)) seekViewport(vp) else pushViewport(vp)
grid.draw(gtable)
upViewport()
}
invisible(data)
}
#' @rdname print.ggplot
#' @method plot ggplot
#' @export
plot.ggplot <- print.ggplot
#' Generate a ggplot2 plot grob.
#'
#' @param x ggplot2 object
#' @keywords internal
#' @export
ggplotGrob <- function(x) {
ggplot_gtable(ggplot_build(x))
}