Attached are two patches to make --with-cairo builds more usable.

First patch tries to fix screen corruption, and the second patch allows
cairo builds to display images.

These patches are only slightly tested, but I hope they will be useful.

In GNU Emacs 27.0.50 (build 10, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2018-04-27 built on arirop
Repository revision: caa93364d47bd28633cc065e31dd5972a1e916d5
Windowing system distributor 'Fedora Project', version 11.0.11906000
System Description: Fedora 28 (Twenty Eight)