For some reason i can't use phantomJs, which does not have a rendered page view-port.
How can I turn off view-port in slimerJs?
one of the solutions is:
var page = require('webpage').create();
page.viewportSize = {width: 0; height: 0},
but with this I get unwanted pop-ups.
You can turn off view-port on Linux.
You should install xvfb. SlimerJs docs