problem

The descriptions for the x and y properties on Page.Viewport are sufficiently vague in the context of Page.captureScreenshot.clip that the Puppeteer team made the mistake of interpreting them as x and y values for the element relative to the current viewport.

Unfortunately, they are actually used in Chromium as x and y values for the viewport relative to the document.

solution

I would suggest clarifying the description strings for these properties.

relevant code

Puppeteer issue describing the problem

puppeteer/puppeteer#1315

Puppeteer PR to resolve the mistake

puppeteer/puppeteer#1323

Chromium usage

https://github.com/ChromeDevTools/devtools-protocol/blob/master/json/browser_protocol.json#L262-L263