Shadow blur is quite larger compared to web browsers
Google Chrome (left) vs GTK master with GL renderer (right):
box-shadow: 0 0 4px red:
box-shadow: 0 0 8px red:
box-shadow: 0 0 16px red:
This could be a problem when designers need a subtle blur. (See #2033 (closed) for example.)
Just for reference: I used Google Chrome here for screenshots, but there is almost no difference in blur size between Firefox and Google Chrome.
GTK version: master