I propose that this was fixed in r157 onJuly 2nd.
Let's look at how the exception could occur, follow along with grep at
home for fun:
Starting with just the mir tree:
1. The exception can only occur in the InputRegistrar::handle_for_channel
(android_input_registrar.cpp).
2. handle_for_channel is only invoked from the InputTargetEnumerator and the
InputTargeter.
Let's break things down to find the cause of the exception
0. We can see QtMir does not directly use handle_for_channel
1. The InputTargetEnumerator, this is only used by the InputDispatcher. Of
course, in qtmir the InputDispatcher is replaced with the QtEventFeeder, so it
can not be Mir's usage of the InputTargetEnumerator triggering the exception.
We can see the QtMir tree does not directly use the InputTargetEnumerator
either, so we can rule it out as the cause of the exception.
2. The InputTargeter is the remaining culprit and its only used by the shell
focus setter.
If we dig in to QtMir though we see
1. The InputTargeter is not used directly
2. The shell focus setter is overriden with a noop
By this logic we have shown that handle_for_channel is never called in
QtMir (and why would it be? It's purely used to translate between
InputDispatcher android types and MirSurfaces to avoid leaking the
android input window interface in to the Mir surface interface...as the
InputDispatcher is eliminated this code should be as well). However
clearly this exception was observed at one point so we must provide an
explanation:
bzr blame focussetter.cpp draws our attention to revision 157 (I suggest
skimming bzr diff 156..157 as the committ message is a little
misleading). We can see prior to r157 QtMir was not overriding the shell
focus setter and making use of the default mir impl, thusly making use
of the InputTargeter. We can also see application_manager.cpp making
direct use of the_focus_controller()->set_focus_to( thus invoking the
input targeter. One feasible explanation for the race is that depending
on the ordering of observer registration the application manager may be
notified surface removal after the input registrar has processed them.
None-the-less I am satisfied that this code path is no longer active and
thus closing the bug as fix released.
** Also affects: qtmir
Importance: Undecided
Status: New
** Changed in: mir
Status: Triaged => Invalid
** Changed in: qtmir
Status: New => Fix Released
** Changed in: mir/0.6
Status: Triaged => Invalid
** Changed in: mir (Ubuntu)
Status: New => Invalid
** Changed in: unity8 (Ubuntu)
Status: New => Fix Released
** Changed in: qtmir
Importance: Undecided => High
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https://bugs.launchpad.net/bugs/1292472
Title:
unity8 crashed with what(): Requesting handle for an unregistered
channel
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