Zoom out of website when using RSelenium without changing page size/resolution

Question

I'd like to zoom out of RSelenium remote, but this is surprisingly difficult to find a solution. I am aware of

• How to zoom out page using RSelenium library in R?, but I woud like to not adjust the page size or the resolution---simply zoom out.
• I have pondered sending control + substract simultaneously, but this is also not quite working. I have taken a look at How to press two keys simultaneously (i.e., control-s) in a webpage using RSelenium?, which as the OP noted, control + a worked but not control + s, and subsequently control + substract didn't work either.
• I also tried the Unicode method specified in How to send simultaneous keys in RSelenium ALT+S to web driver?, which did not work either.

library(RSelenium)
driver <- rsDriver()
remDr <- driver[["client"]]
remDr$navigate("https://www.google.com/")
webElem <- remDr$findElement("css", "html")
webElem$sendKeysToElement(list(key = "control", "-"))              ## Does not work
webElem$sendKeysToElement(list(key = "control", key = "subtract")) ## Does not work

The browser is Chrome.

Answer 1

I don't think the problem is with sending the keys to the browser, since as noted in the linked posts, it is possible to send control + a to the browser window to select elements. It seems rather that the keys are not being recognised as commands to the browser application.

There are other ways round this problem however.

As @Muzzamil suggests, you can get a similar effect with changing the css of the document body using Chrome, though this doesn't work in Firefox.

If you want to natively change the browser zoom in a way that persists throughout the session, I can demonstrate solutions using Firefox and Chrome, since in both cases one can navigate to the html-based options page and interact with it to set the browser zoom level.

Here's how you do it with Firefox:

library(RSelenium)

zoom_firefox <- function(client, percent)
{
  store_page <- client$getCurrentUrl()[[1]]
  client$navigate("about:preferences")
  webElem <- client$findElement("css", "#defaultZoom")
  webElem$clickElement()
  webElem$sendKeysToElement(list(as.character(percent)))
  webElem$sendKeysToElement(list(key = "return"))
  client$navigate(store_page)
}

This allows the following:

driver <- rsDriver(browser = "firefox")
client <- driver$client
client$navigate("https://www.google.com")
client$screenshot(display = TRUE)

We can see the default zoom is set (100%):

Now we zoom out to 50% like this:

zoom_firefox(client, 50)
client$screenshot(display = TRUE)

And zoom back in like this:

zoom_firefox(client, 100)
client$screenshot(display = TRUE)

It's harder with Chrome because its options page uses a complex, nested shadow DOM. Since we can't get an xpath or css selectors to navigate a shadow dom, we need to extract the element's webdriver id using javascript and then force this Id onto another web element which we can then control.

zoom_chrome <- function(client, percent)
{
  store_page <- client$getCurrentUrl()[[1]]
  client$navigate("chrome://settings/")
  webElemId <- client$executeScript(paste0("return document.querySelector",
                                           "(\"body > settings-ui\").",
                                           "shadowRoot.querySelector(\"#main\")",
                                           ".shadowRoot.querySelector",
                                           "(\"settings-basic-page\")",
                                           ".shadowRoot.querySelector",
                                           "(\"#basicPage > ",
                                           "settings-section:nth-child(8)",
                                           "> settings-appearance-page\")",
                                           ".shadowRoot.querySelector",
                                           "(\"#zoomLevel\");"),
                                    args = list("dummy"))
  webElem <- client$findElement("css", "html")
  webElem@.xData$elementId <- as.character(webElemId)
  webElem$clickElement()
  webElem$sendKeysToElement(list("3"))
  zooms <- c(25, 33, 50, 67, 75, 8:11 * 10, 125, 150, 175, 200, 250, 3:5 * 100)
  desired_zoom <- which.min(abs(percent - zooms))
  current_zoom <- which(zooms == 300)
  n_keys <- desired_zoom - current_zoom
  if(n_keys > 0) 
    for(i in seq(n_keys)) 
      webElem$sendKeysToElement(list(key = "down_arrow"))
  if(n_keys < 0) 
    for(i in seq(abs(n_keys))) 
      webElem$sendKeysToElement(list(key = "up_arrow")) 
  webElem$sendKeysToElement(list(as.character(percent)))
  webElem$sendKeysToElement(list(key = "return"))
  client$navigate(store_page)
}

But it works in the same way:

driver <- rsDriver(browser = "chrome", chromever = "80.0.3987.106")
client <- driver$client
client$navigate("https://www.google.com")
client$screenshot(display = TRUE)
zoom_chrome(client, 50)
client$screenshot(display = TRUE)
zoom_chrome(client, 100)
client$screenshot(display = TRUE)

Which gives exactly the same results as firefox.

Of course, you could easily write a simple wrapper function that selects which "zoom" function to call based on the current browser.

I have not looked into implementing this in internet explorer or phantomjs since they do not have html-based options pages.

Answer 2

You can try Zoom out with Java script. Please try below code for zoom out at 90%.

library(RSelenium)
driver <- rsDriver()
remDr <- driver[["client"]]
remDr$navigate("https://www.google.com/")
webElem <- remDr$findElement("css", "html")
script <- "document.body.style.zoom='90%'" 
remDr$executeScript(script, args = list())