|User since||Sept. 4, 2013|
|Number of add-ons developed||0 add-ons|
|Average rating of developer's add-ons||Not yet rated|
correct ViewportSize Rated 4 out of 5 stars
@McGWD: nice work, but the viewport is actually content.document.documentElement.clientWidth
document.documentElement.clientWidth in that case returns the size of the whole program window. Seems the addon is not working in the document window scope by default.