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chrome.R
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chrome.R
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#' Local Chrome process
#'
#' This is a subclass of [`Browser`] that represents a local browser. It extends
#' the [`Browser`] class with a [`processx::process`] object, which represents
#' the browser's system process.
#' @export
Chrome <- R6Class("Chrome",
inherit = Browser,
public = list(
#' @description Create a new Chrome object.
#' @param path Location of chrome installation
#' @param args A character vector of command-line arguments passed when
#' initializing Chrome. Single on-off arguments are passed as single
#' values (e.g.`"--disable-gpu"`), arguments with a value are given with a
#' nested character vector (e.g. `c("--force-color-profile", "srgb")`).
#' See
#' [here](https://peter.sh/experiments/chromium-command-line-switches/)
#' for a list of possible arguments. Defaults to [`get_chrome_args()`].
#' @return A new `Chrome` object.
#' @seealso [`get_chrome_args()`]
initialize = function(path = find_chrome(), args = get_chrome_args()) {
if (is.null(path)) {
stop("Invalid path to Chrome")
}
res <- launch_chrome(path, args)
private$host <- "127.0.0.1"
private$process <- res$process
private$port <- res$port
private$path <- path
},
#' @description Browser application path
get_path = function() private$path
),
private = list(
path = NULL
)
)
#' Find path to Chrome or Chromium browser
#' @export
find_chrome <- function() {
if (Sys.getenv("CHROMOTE_CHROME") != "") {
return(Sys.getenv("CHROMOTE_CHROME"))
}
path <- NULL
if (is_mac()) {
path <- "/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome"
} else if (is_windows()) {
tryCatch(
{
path <- utils::readRegistry("SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\App Paths\\chrome.exe\\")
path <- path[["(Default)"]]
},
error = function(e) {
message("Error trying to find path to Chrome")
path <<- NULL
}
)
} else if (is_linux()) {
path <- Sys.which("google-chrome")
if (nchar(path) == 0) {
path <- Sys.which("chromium-browser")
}
if (nchar(path) == 0) {
path <- Sys.which("chromium")
}
if (nchar(path) == 0) {
message("`google-chrome` and `chromium-browser` were not found. Try setting the CHROMOTE_CHROME environment variable or adding one of these executables to your PATH.")
path <- NULL
}
} else {
message("Platform currently not supported")
}
path
}
launch_chrome <- function(path = find_chrome(), args = get_chrome_args()) {
if (is.null(path)) {
stop("Invalid path to Chrome")
}
p <- process$new(
command = path,
args = c("--headless", "--remote-debugging-port=0", args),
supervise = TRUE,
stdout = tempfile("chrome-stdout-", fileext = ".log"),
stderr = tempfile("chrome-stderr-", fileext = ".log")
)
connected <- FALSE
end <- Sys.time() + 10
while (!connected && Sys.time() < end) {
if (!p$is_alive()) {
stop(
"Failed to start chrome. Error: ",
paste(readLines(p$get_error_file()), collapse = "\n")
)
}
tryCatch(
{
# Find port number from output
output <- readLines(p$get_error_file())
output <- output[grepl("^DevTools listening on ws://", output)]
if (length(output) != 1) stop() # Just break out of the tryCatch
port <- sub("^DevTools listening on ws://[0-9\\.]+:(\\d+)/.*", "\\1", output)
port <- as.integer(port)
if (is.na(port)) stop()
con <- url(paste0("http://127.0.0.1:", port, "/json/protocol"), "rb")
if (!isOpen(con)) break # Failed to connect
connected <- TRUE
close(con)
},
warning = function(e) {},
error = function(e) {}
)
Sys.sleep(0.1)
}
if (!connected) {
stop("Chrome debugging port not open after 10 seconds.")
}
list(
process = p,
port = port
)
}
#' Remote Chrome process
#'
#'
#'
#' @export
ChromeRemote <- R6Class("ChromeRemote",
inherit = Browser,
public = list(
#' @description Create a new ChromeRemote object.
#' @param host A string that is a valid IPv4 or IPv6 address. `"0.0.0.0"`
#' represents all IPv4 addresses and `"::/0"` represents all IPv6 addresses.
#' @param port A number or integer that indicates the server port.
initialize = function(host, port) {
private$host <- host
private$port <- port
}
)
)