ChromoteSession class

Public fields

parent: Chromote object
default_timeout: Default timeout in seconds for chromote to wait for a Chrome DevTools Protocol response.
protocol: Dynamic protocol implementation. For expert use only!

Methods

Public methods

ChromoteSession$new()
ChromoteSession$view()
ChromoteSession$close()
ChromoteSession$screenshot()
ChromoteSession$screenshot_pdf()
ChromoteSession$new_session()
ChromoteSession$get_session_id()
ChromoteSession$wait_for()
ChromoteSession$debug_log()
ChromoteSession$get_child_loop()
ChromoteSession$send_command()
ChromoteSession$get_auto_events()
ChromoteSession$invoke_event_callbacks()
ChromoteSession$mark_closed()
ChromoteSession$is_active()
ChromoteSession$init_promise()

Method `new()`

Create a new ChromoteSession object.

Usage

ChromoteSession$new(
  parent = default_chromote_object(),
  width = 992,
  height = 1323,
  targetId = NULL,
  wait_ = TRUE,
  auto_events = NULL
)

Arguments

parent: Chromote object to use; defaults to default_chromote_object()
width: Width, in pixels, of the Target to create if targetId is NULL
height: Height, in pixels, of the Target to create if targetId is NULL
targetId: Target ID of an existing target to attach to. When a targetId is provided, the width and height arguments are ignored. If NULL (the default) a new target is created and attached to, and the width and height arguments determine its viewport size.
wait_: If FALSE, return a promises::promise() of a new ChromoteSession object. Otherwise, block during initialization, and return a ChromoteSession object directly.
auto_events: If NULL (the default), use the auto_events setting from the parent Chromote object. If TRUE, enable automatic event enabling/disabling; if FALSE, disable automatic event enabling/disabling.

Returns

A new ChromoteSession object.

Examples

\dontrun{# Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Create a ChromoteSession with a specific height,width
b <- ChromoteSession$new(height = 1080, width = 1920)

# Navigate to page
b$Page$navigate("http://www.r-project.org/")

# View current chromote session
if (interactive()) b$view()}

Method `view()`

Display the current session in the Chromote browser.

If a Chrome browser is being used, this method will open a new tab using your Chrome browser. When not using a Chrome browser, set options(browser=) to change the default behavior of browseURL().

Usage

ChromoteSession$view()

Examples

\dontrun{# Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Navigate to page
b$Page$navigate("http://www.r-project.org/")

# View current chromote session
if (interactive()) b$view()}

Method `close()`

Close the Chromote session.

Usage

ChromoteSession$close(wait_ = TRUE)

Arguments

wait_: If FALSE, return a promises::promise() that will resolve when the ChromoteSession is closed. Otherwise, block until the ChromoteSession has closed.

Examples

\dontrun{# Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Navigate to page
b$Page$navigate("http://www.r-project.org/")

# Close current chromote session
b$close()}

Method `screenshot()`

Take a PNG screenshot

Usage

ChromoteSession$screenshot(
  filename = "screenshot.png",
  selector = "html",
  cliprect = NULL,
  region = c("content", "padding", "border", "margin"),
  expand = NULL,
  scale = 1,
  show = FALSE,
  delay = 0.5,
  wait_ = TRUE
)

Arguments

filename: File path of where to save the screenshot.
selector: CSS selector to use for the screenshot.
cliprect: A list containing x, y, width, and height. See Page.Viewport for more information. If provided, selector and expand will be ignored. To provide a scale, use the scale parameter.
region: CSS region to use for the screenshot.
expand: Extra pixels to expand the screenshot. May be a single value or a numeric vector of top, right, bottom, left values.
scale: Page scale factor
show: If TRUE, the screenshot will be displayed in the viewer.
delay: The number of seconds to wait before taking the screenshot after resizing the page. For complicated pages, this may need to be increased.
wait_: If FALSE, return a promises::promise() that will resolve when the ChromoteSession has saved the screenshot. Otherwise, block until the ChromoteSession has saved the screenshot.

Examples

\dontrun{# Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Navigate to page
b$Page$navigate("http://www.r-project.org/")

# Take screenshot
tmppngfile <- tempfile(fileext = ".png")
is_interactive <- interactive() # Display screenshot if interactive
b$screenshot(tmppngfile, show = is_interactive)

# Show screenshot file info
unlist(file.info(tmppngfile))


# Take screenshot using a selector
sidebar_file <- tempfile(fileext = ".png")
b$screenshot(sidebar_file, selector = ".sidebar", show = is_interactive)

# ----------------------------
# Take screenshots in parallel

urls <- c(
  "https://www.r-project.org/",
  "https://github.com/",
  "https://news.ycombinator.com/"
)
# Helper method that:
# 1. Navigates to the given URL
# 2. Waits for the page loaded event to fire
# 3. Takes a screenshot
# 4. Prints a message
# 5. Close the ChromoteSession
screenshot_p <- function(url, filename = NULL) {
  if (is.null(filename)) {
    filename <- gsub("^.*://", "", url)
    filename <- gsub("/", "_", filename)
    filename <- gsub("\\.", "_", filename)
    filename <- sub("_$", "", filename)
    filename <- paste0(filename, ".png")
  }

  b2 <- b$new_session()
  b2$Page$navigate(url, wait_ = FALSE)
  b2$Page$loadEventFired(wait_ = FALSE)$
    then(function(value) {
      b2$screenshot(filename, wait_ = FALSE)
    })$
    then(function(value) {
      message(filename)
    })$
    finally(function() {
      b2$close()
    })
}

# Take multiple screenshots simultaneously
ps <- lapply(urls, screenshot_p)
pa <- promises::promise_all(.list = ps)$then(function(value) {
  message("Done!")
})

# Block the console until the screenshots finish (optional)
b$wait_for(pa)
#> www_r-project_org.png
#> github_com.png
#> news_ycombinator_com.png
#> Done!}

Method `screenshot_pdf()`

Take a PDF screenshot

Usage

ChromoteSession$screenshot_pdf(
  filename = "screenshot.pdf",
  pagesize = "letter",
  margins = 0.5,
  units = c("in", "cm"),
  landscape = FALSE,
  display_header_footer = FALSE,
  print_background = FALSE,
  scale = 1,
  wait_ = TRUE
)

Arguments

filename: File path of where to save the screenshot.
pagesize: A single character value in the set "letter", "legal", "tabloid", "ledger" and "a0" through "a1". Or a numeric vector c(width, height) specifying the page size.
margins: A numeric vector c(top, right, bottom, left) specifying the page margins.
units: Page and margin size units. Either "in" or "cm" for inches and centimeters respectively.
landscape: Paper orientation.
display_header_footer: Display header and footer.
print_background: Print background graphics.
scale: Page scale factor.
wait_: If FALSE, return a promises::promise() that will resolve when the ChromoteSession has saved the screenshot. Otherwise, block until the ChromoteSession has saved the screnshot.

Examples

\dontrun{# Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Navigate to page
b$Page$navigate("http://www.r-project.org/")

# Take screenshot
tmppdffile <- tempfile(fileext = ".pdf")
b$screenshot_pdf(tmppdffile)

# Show PDF file info
unlist(file.info(tmppdffile))}

Method `new_session()`

Create a new tab / window

Usage

ChromoteSession$new_session(
  width = 992,
  height = 1323,
  targetId = NULL,
  wait_ = TRUE
)

Arguments

width, height: Width and height of the new window.
targetId: Target ID of an existing target to attach to. When a targetId is provided, the width and height arguments are ignored. If NULL (the default) a new target is created and attached to, and the width and height arguments determine its viewport size.
wait_: If FALSE, return a promises::promise() that will resolve when the ChromoteSession has created a new session. Otherwise, block until the ChromoteSession has created a new session.

Examples

\dontrun{b1 <- ChromoteSession$new()
b1$Page$navigate("http://www.google.com")
b2 <- b1$new_session()
b2$Page$navigate("http://www.r-project.org/")
b1$Runtime$evaluate("window.location", returnByValue = TRUE)$result$value$href
#> [1] "https://www.google.com/"
b2$Runtime$evaluate("window.location", returnByValue = TRUE)$result$value$href
#> [1] "https://www.r-project.org/"}

Method `get_session_id()`

Retrieve the session id

Usage

ChromoteSession$get_session_id()

Examples

\dontrun{b <- ChromoteSession$new()
b$get_session_id()
#> [1] "05764F1D439F4292497A21C6526575DA"}

Method `wait_for()`

Wait for a Chromote Session to finish. This method will block the R session until the provided promise resolves. The loop from $get_child_loop() will only advance just far enough for the promise to resolve.

Usage

ChromoteSession$wait_for(p)

Arguments

p: A promise to resolve.

Examples

\dontrun{b <- ChromoteSession$new()

# Async with promise
p <- b$Browser$getVersion(wait_ = FALSE)
p$then(str)

# Async with callback
b$Browser$getVersion(wait_ = FALSE, callback_ = str)}

Method `debug_log()`

Send a debug log message to the parent Chromote object

Usage

ChromoteSession$debug_log(...)

Arguments

...: Arguments pasted together with paste0(..., collapse = "").

Examples

\dontrun{b <- ChromoteSession$new()
b$parent$debug_messages(TRUE)
b$Page$navigate("https://www.r-project.org/")
#> SEND {"method":"Page.navigate","params":{"url":"https://www.r-project.org/"}| __truncated__}
# Turn off debug messages
b$parent$debug_messages(FALSE)}

Method `get_child_loop()`

later loop.

For expert async usage only.

Usage

ChromoteSession$get_child_loop()

Method `send_command()`

Send command through Chrome DevTools Protocol.

For expert use only.

Usage

ChromoteSession$send_command(
  msg,
  callback = NULL,
  error = NULL,
  timeout = NULL
)

Arguments

msg: A JSON-serializable list containing method, and params.
callback: Method to run when the command finishes successfully.
error: Method to run if an error occurs.
timeout: Number of milliseconds for Chrome DevTools Protocol execute a method.

Method `get_auto_events()`

Resolved auto_events value.

For internal use only.

Usage

ChromoteSession$get_auto_events()

Method `invoke_event_callbacks()`

Immediately call all event callback methods.

For internal use only.

Usage

ChromoteSession$invoke_event_callbacks(event, params)

Arguments

event: A single event string
params: A list of parameters to pass to the event callback methods.

Method `mark_closed()`

Disable callbacks for a given session.

For internal use only.

Usage

ChromoteSession$mark_closed()

Method `is_active()`

Retrieve active status Once initialized, the value returned is TRUE. If $close() has been called, this value will be FALSE.

Usage

ChromoteSession$is_active()

Method `init_promise()`

Initial promise

For internal use only.

Usage

ChromoteSession$init_promise()

Examples


## ------------------------------------------------
## Method `ChromoteSession$new`
## ------------------------------------------------

if (FALSE) # Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Create a ChromoteSession with a specific height,width
b <- ChromoteSession$new(height = 1080, width = 1920)

# Navigate to page
b$Page$navigate("http://www.r-project.org/")
#> $frameId
#> [1] "E2F5E76113BBDD7B2BB0E7ABEF03ADF2"
#> 
#> $loaderId
#> [1] "1D4C2BF02AC59DE1AE973C16E5B384E4"
#> 

# View current chromote session
if (interactive()) b$view()

## ------------------------------------------------
## Method `ChromoteSession$view`
## ------------------------------------------------

if (FALSE) # Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Navigate to page
b$Page$navigate("http://www.r-project.org/")
#> $frameId
#> [1] "E2F5E76113BBDD7B2BB0E7ABEF03ADF2"
#> 
#> $loaderId
#> [1] "7B2E203B1675F55E970631A51A3D417B"
#> 

# View current chromote session
if (interactive()) b$view()

## ------------------------------------------------
## Method `ChromoteSession$close`
## ------------------------------------------------

if (FALSE) # Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Navigate to page
b$Page$navigate("http://www.r-project.org/")
#> $frameId
#> [1] "E2F5E76113BBDD7B2BB0E7ABEF03ADF2"
#> 
#> $loaderId
#> [1] "6C68606782C7E786A1238FE12AE3E9AD"
#> 

# Close current chromote session
b$close()
#> [1] TRUE

## ------------------------------------------------
## Method `ChromoteSession$screenshot`
## ------------------------------------------------

if (FALSE) # Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Navigate to page
b$Page$navigate("http://www.r-project.org/")
#> Error in self$send_command(msg, callback = callback_, error = error_,     timeout = timeout_): Session 398DBEC869667CE0EF0692612A8E6CE0 is closed.

# Take screenshot
tmppngfile <- tempfile(fileext = ".png")
is_interactive <- interactive() # Display screenshot if interactive
b$screenshot(tmppngfile, show = is_interactive)
#> Error in self$send_command(msg, callback = callback_, error = error_,     timeout = timeout_): Session 398DBEC869667CE0EF0692612A8E6CE0 is closed.

# Show screenshot file info
unlist(file.info(tmppngfile))
#>   size  isdir   mode  mtime  ctime  atime    uid    gid  uname grname 
#>     NA     NA     NA     NA     NA     NA     NA     NA     NA     NA 


# Take screenshot using a selector
sidebar_file <- tempfile(fileext = ".png")
b$screenshot(sidebar_file, selector = ".sidebar", show = is_interactive)
#> Error in self$send_command(msg, callback = callback_, error = error_,     timeout = timeout_): Session 398DBEC869667CE0EF0692612A8E6CE0 is closed.

# ----------------------------
# Take screenshots in parallel

urls <- c(
  "https://www.r-project.org/",
  "https://github.com/",
  "https://news.ycombinator.com/"
)
# Helper method that:
# 1. Navigates to the given URL
# 2. Waits for the page loaded event to fire
# 3. Takes a screenshot
# 4. Prints a message
# 5. Close the ChromoteSession
screenshot_p <- function(url, filename = NULL) {
  if (is.null(filename)) {
    filename <- gsub("^.*://", "", url)
    filename <- gsub("/", "_", filename)
    filename <- gsub("\\.", "_", filename)
    filename <- sub("_$", "", filename)
    filename <- paste0(filename, ".png")
  }

  b2 <- b$new_session()
  b2$Page$navigate(url, wait_ = FALSE)
  b2$Page$loadEventFired(wait_ = FALSE)$
    then(function(value) {
      b2$screenshot(filename, wait_ = FALSE)
    })$
    then(function(value) {
      message(filename)
    })$
    finally(function() {
      b2$close()
    })
}

# Take multiple screenshots simultaneously
ps <- lapply(urls, screenshot_p)
pa <- promises::promise_all(.list = ps)$then(function(value) {
  message("Done!")
})

# Block the console until the screenshots finish (optional)
b$wait_for(pa)
#> NULL
#> www_r-project_org.png
#> github_com.png
#> news_ycombinator_com.png
#> Done!

## ------------------------------------------------
## Method `ChromoteSession$screenshot_pdf`
## ------------------------------------------------

if (FALSE) # Create a new `ChromoteSession` object.
b <- ChromoteSession$new()

# Navigate to page
b$Page$navigate("http://www.r-project.org/")
#> Error in self$send_command(msg, callback = callback_, error = error_,     timeout = timeout_): Session 398DBEC869667CE0EF0692612A8E6CE0 is closed.

# Take screenshot
tmppdffile <- tempfile(fileext = ".pdf")
b$screenshot_pdf(tmppdffile)
#> Error in self$send_command(msg, callback = callback_, error = error_,     timeout = timeout_): Session 398DBEC869667CE0EF0692612A8E6CE0 is closed.

# Show PDF file info
unlist(file.info(tmppdffile))
#>   size  isdir   mode  mtime  ctime  atime    uid    gid  uname grname 
#>     NA     NA     NA     NA     NA     NA     NA     NA     NA     NA 

## ------------------------------------------------
## Method `ChromoteSession$new_session`
## ------------------------------------------------

if (FALSE) b1 <- ChromoteSession$new()
b1$Page$navigate("http://www.google.com")
#> Error in eval(expr, envir, enclos): object 'b1' not found
b2 <- b1$new_session()
#> Error in eval(expr, envir, enclos): object 'b1' not found
b2$Page$navigate("http://www.r-project.org/")
#> Error in eval(expr, envir, enclos): object 'b2' not found
b1$Runtime$evaluate("window.location", returnByValue = TRUE)$result$value$href
#> Error in eval(expr, envir, enclos): object 'b1' not found
#> [1] "https://www.google.com/"
b2$Runtime$evaluate("window.location", returnByValue = TRUE)$result$value$href
#> Error in eval(expr, envir, enclos): object 'b2' not found
#> [1] "https://www.r-project.org/"

## ------------------------------------------------
## Method `ChromoteSession$get_session_id`
## ------------------------------------------------

if (FALSE) b <- ChromoteSession$new()
b$get_session_id()
#> [1] "398DBEC869667CE0EF0692612A8E6CE0"
#> [1] "05764F1D439F4292497A21C6526575DA"

## ------------------------------------------------
## Method `ChromoteSession$wait_for`
## ------------------------------------------------

if (FALSE) b <- ChromoteSession$new()

# Async with promise
p <- b$Browser$getVersion(wait_ = FALSE)
#> Error in self$send_command(msg, callback = callback_, error = error_,     timeout = timeout_): Session 398DBEC869667CE0EF0692612A8E6CE0 is closed.
p$then(str)
#> Error in eval(expr, envir, enclos): object 'p' not found

# Async with callback
b$Browser$getVersion(wait_ = FALSE, callback_ = str)
#> Error in self$send_command(msg, callback = callback_, error = error_,     timeout = timeout_): Session 398DBEC869667CE0EF0692612A8E6CE0 is closed.

## ------------------------------------------------
## Method `ChromoteSession$debug_log`
## ------------------------------------------------

if (FALSE) b <- ChromoteSession$new()
b$parent$debug_messages(TRUE)
b$Page$navigate("https://www.r-project.org/")
#> Error in self$send_command(msg, callback = callback_, error = error_,     timeout = timeout_): Session 398DBEC869667CE0EF0692612A8E6CE0 is closed.
#> SEND {"method":"Page.navigate","params":{"url":"https://www.r-project.org/"}| __truncated__}
# Turn off debug messages
b$parent$debug_messages(FALSE)

ChromoteSession class

Public fields

Methods

Public methods

Method new()

Usage

Arguments

Returns

Examples

Method view()

Usage

Examples

Method close()

Usage

Arguments

Examples

Method screenshot()

Usage

Arguments

Examples

Method screenshot_pdf()

Usage

Arguments

Examples

Method new_session()

Usage

Arguments

Examples

Method get_session_id()

Usage

Examples

Method wait_for()

Usage

Arguments

Examples

Method debug_log()

Usage

Arguments

Examples

Method get_child_loop()

Usage

Method send_command()

Usage

Arguments

Method get_auto_events()

Usage

Method invoke_event_callbacks()

Usage

Arguments

Method mark_closed()

Usage

Method is_active()

Usage

Method init_promise()

Usage

Examples

Method `new()`

Method `view()`

Method `close()`

Method `screenshot()`

Method `screenshot_pdf()`

Method `new_session()`

Method `get_session_id()`

Method `wait_for()`

Method `debug_log()`

Method `get_child_loop()`

Method `send_command()`

Method `get_auto_events()`

Method `invoke_event_callbacks()`

Method `mark_closed()`

Method `is_active()`

Method `init_promise()`