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#' Convert a base plot or a ggplot2 plot into a grob
#'
#' This function does its best attempt to take whatever you provide it and turn it into a grob.
#' It is primarily meant to convert ggplot plots into grobs, but it will also take any grid
#' object (grob), a recorded base R plot, a formula specifying a base R plot, a function that
#' generates a base R plot, or a trellis object.
#'
#' @param plot The plot to convert
#' @param device A function that creates an appropriate null device. See [`set_null_device()`]
#' for details. If set to `NULL`, will use the cowplot-wide default.
#'
#' @examples
#' library(grid)
#' x <- 1:10
#' y <- (1:10)^2
#'
#' p <- ~plot(x, y)
#' grid.newpage()
#' grid.draw(as_grob(p))
#' @export
as_grob <- function(plot, device = NULL) {
UseMethod("as_grob")
}
#' @export
as_grob.recordedplot <- function(plot, device = NULL) {
if (!requireNamespace("gridGraphics", quietly = TRUE)){
warning("Package `gridGraphics` is required to handle base-R plots. Substituting empty plot.", call. = FALSE)
grid::nullGrob()
}
else {
if (is.null(device)) {
device <- null_dev_env$current
}
gridGraphics::echoGrob(plot, device = device)
}
}
#' @export
as_grob.trellis <- function(plot, device = NULL) {
if (is.null(device)) {
device <- null_dev_env$current
}
grid::recordGrob(
tryCatch(
print(plot, newpage=FALSE),
error = function(e) {
grid::grid.text(e$message)
}
), list(plot = plot, device = device))
}
#' @export
as_grob.function <- function(plot, device = NULL) {
# functions are handled just like recorded plots:
as_grob.recordedplot(plot, device)
}
#' @export
as_grob.formula <- function(plot, device = NULL) {
expr <- plot[[2]]
env <- parent.frame()
f <- function() {eval(expr, envir = env)}
# functions are handled just like recorded plots:
as_grob.recordedplot(f, device)
}
#' @export
as_grob.grob <- function(plot, device = NULL) {
# grobs don't have to be converted
plot
}
#' @export
as_grob.gList <- function(plot, device = NULL) {
# gLists need to be wrapped in a grob tree
grid::grobTree(plot)
}
#' @export
as_grob.ggplot <- function(plot, device = NULL) {
# Convert ggplot plot to grob
#
# To be safe this works as expected, we have to do some graphics-device gymnastics.
# We need to save and restore the current graphics device, and we also need to open
# a null device. If we don't do this, things may go wrong, in particular in R Studio
# or shiny, such as plots popping up in the wrong location or spurious empty plots
# appearing in knitr. Also, depending on which null device we choose, non-standard
# fonts may or may not work. Different null devices work best in different environments,
# that's why the null device is configurable. (`pdf(NULL)` is the most robust but
# can't handle all fonts, `png()` works well on OS X but creates spurious output files,
# `Cairo(type = "raster")` works well on Windows but font-handling is broken on OS X.)
if (is.null(device)) {
device <- null_dev_env$current
}
cur_dev <- grDevices::dev.cur() # store current device
device(width = 6, height = 6) # open null device
null_dev <- grDevices::dev.cur() # store null device
# make sure we always clean up properly, even if something causes an error
on.exit({
grDevices::dev.off(null_dev)
if (cur_dev > 1) grDevices::dev.set(cur_dev) # only set cur device if not null device
})
ggplot2::ggplotGrob(plot) # convert plot to grob
}
# comment out until patchwork is officially released and on CRAN
#' @export
as_grob.patchwork <- function(plot, device = NULL) {
if (!requireNamespace("patchwork", quietly = TRUE)){
warning("Package `patchwork` is required to handle object of class patchwork. Substituting empty plot.", call. = FALSE)
return(grid::nullGrob())
}
# Convert patchwork ggassemble to grob
#
# To be safe this works as expected, we have to do some graphics-device gymnastics.
# We need to save and restore the current graphics device, and we also need to open
# a null device. If we don't do this, things may go wrong, in particular in R Studio
# or shiny, such as plots popping up in the wrong location or spurious empty plots
# appearing in knitr. Also, depending on which null device we choose, non-standard
# fonts may or may not work. Different null devices work best in different environments,
# that's why the null device is configurable. (`pdf(NULL)` is the most robust but
# can't handle all fonts, `png()` works well on OS X but creates spurious output files,
# `Cairo(type = "raster")` works well on Windows but font-handling is broken on OS X.)
if (is.null(device)) {
device <- null_dev_env$current
}
cur_dev <- grDevices::dev.cur() # store current device
device(width = 6, height = 6) # open null device
null_dev <- grDevices::dev.cur() # store null device
# make sure we always clean up properly, even if something causes an error
on.exit({
grDevices::dev.off(null_dev)
if (cur_dev > 1) grDevices::dev.set(cur_dev) # only set cur device if not null device
})
patchwork::patchworkGrob(plot) # convert plot to grob
}
#' @export
as_grob.default <- function(plot, device = NULL) {
warning("Cannot convert object of class ", class(plot), " into a grob.")
grid::nullGrob()
}
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