Add information about resizing window

README.Rmd

@@ -945,6 +945,31 @@ b$screenshot("s3.png", selector = ".page", region = "margin", scale = 2)
 If a vector is passed to `selector`, it will take a screenshot with a rectangle that encompasses all the DOM elements picked out by the selectors. Similarly, if a selector picks out multiple DOM elements, all of them will be in the screenshot region.
 
 
+### Setting width and height of the viewport (window)
+
+The default size of a `ChromoteSession` viewport is 992 by 1323 pixels. You can set the width and height when it is created:
+
+```R
+b <- ChromoteSession$new(width = 390, height = 844)
+
+b$Page$navigate("https://www.r-project.org/")
+b$screenshot("narrow.png")
+```
+
+With an existing `ChromoteSession`, you can set the size with `b$Emulation$setVisibleSize()`:
+
+```R
+b$Emulation$setVisibleSize(width=1600, height=900)
+b$screenshot("wide.png")
+```
+
+You can take a "Retina" (double) resolution screenshot by using `b$screenshot(scale=2)`:
+
+```R
+b$screenshot("wide-2x.png", scale = 2)
+```
+
+
 ### Taking a screenshot of a web page after interacting with it
 
 Headless Chrome provides a remote debugging UI which you can use to interact with the web page. The ChromoteSession's `$view()` method opens a regular browser and navigates to the remote debugging UI.

README.md

@@ -1227,6 +1227,33 @@ rectangle that encompasses all the DOM elements picked out by the
 selectors. Similarly, if a selector picks out multiple DOM elements, all
 of them will be in the screenshot region.
 
+### Setting width and height of the viewport (window)
+
+The default size of a `ChromoteSession` viewport is 992 by 1323 pixels.
+You can set the width and height when it is created:
+
+``` r
+b <- ChromoteSession$new(width = 390, height = 844)
+
+b$Page$navigate("https://www.r-project.org/")
+b$screenshot("narrow.png")
+```
+
+With an existing `ChromoteSession`, you can set the size with
+`b$Emulation$setVisibleSize()`:
+
+``` r
+b$Emulation$setVisibleSize(width=1600, height=900)
+b$screenshot("wide.png")
+```
+
+You can take a “Retina” (double) resolution screenshot by using
+`b$screenshot(scale=2)`:
+
+``` r
+b$screenshot("wide-2x.png", scale = 2)
+```
+
 ### Taking a screenshot of a web page after interacting with it
 
 Headless Chrome provides a remote debugging UI which you can use to