Florian Müllner authored Mar 06, 2019 and Marco Trevisan committed Mar 12, 2019

Traditionally visual alerts were implemented by flashing the focus
window's frame. As that only works for windows that we decorate,
flashing the whole window was added as a fallback for client-decorated
windows.

However that introduces some confusing inconsistency, better to just
always flash the entire window.

#491