Interesting approach I would not have expected to work. A dummy Effect
class is created in the test and an instance is passed to
EffectsHandler's startMouseInterception. It doesn't verify whether it's
an Effect it knows or has created, so it's totally happy with the dummy.
It shows that motion and press/release are passed to the Effect when
screen is not locked and doesn't while the screen is locked.
On the CI system our tests failed due to the greeter failing to start
due to OpenGL problems. This was because we waited for a window to show
which never happened. Thus the test failed.
This change makes use of the new lockStateChanged signal to determine
when the screen gets locked/unlocked.
It's still possible that the test fails as I'm not able to reproduce
the failure condition on the CI system.
First test case is to ensure that pointer motion events trigger a
leave event on the surface the pointer is on.
The test case shows errors in the input handling.
More tests need to be added.
