basically DiffMessage has a "take everything" ctor, which happens
to match on type DiffMessage itslef, since the latter is obviously
a Lumiera Forward Operator. Unfortunately the compiler now considers
this "take everyting" ctor as copy constructor. Worse even, such a
template generated ctor qualifies as "best match".
The result was, when just returing a DiffMessage by value form a
function, this erroneous "copy" operation was invoked, thus wrapping
the existing implementation into a WrappedLumieraIterator.
The only tangible symptom of this unwanted storage bloat was the fact
that our already materialised diagnostics where seemingly "gone". Indee
they weren't gone for real, just covered up under yet another layer of
DiffMessage wrapping another Lumiera Forward Iterator
by moving, we can avoid the generation of up to 3 additional shared copies
of the DataHandle. The whole invocation now works without touching any shared count
and thus without incurring a memory barrier...
this becomes more relevant now, since the actual MutationMessage iterators
are implemented in terms of a shared_ptr to IterSource. Thus, when building
processing pipelines, we most definitively want to move that smart-ptr into
the destination, since this avoids touching the shared count and thus avoids
generating unnecessary memory barriers.
...allows us to get rid of quite some boost-includes
Incidentally, "our own" implementation is equivalent to both the
boost implementation and the implementation from C++14
It is just a bit more concise to write.
since we do not want to increase the footprint, we're bound to reuse
an existing VTable -- so IterAdapter itself is our only option.
Unfortunately we'll need to pass that through one additional
decoration layer, which is here the iterator; to be able to
add our string conversion there, we need to turn that into
a derived class and add a call to access the underlying
container, which gets us into element type definition mess....
now this highlights the unsettled decision still the more,
as can be seen by all that unnecessary copying. Basically we move the
Diff into the lambda-closure, from there into an anonymous instance,
from there into the embedded Buffer in MutationMessage, which again
just happens to sit in the closure storage when the action is invoked.
And all of this copying just to move the DiffMessage for consumption
into the TreeMutator...
thus by #1066 we should really get rid of the MutationMessage class altogether!
actually I do not know much regarding the actual situation when,
within the Builder run, we're able to detect a change and generate
a diff description. However, as a first step, I'll pick IterSrouce
as a base interface and use a "generation context", which is to be
passed by shared-ptr
basically we want a non-modal notification box in the UI,
which normally stays out of the way. A good example of how such
can be accomplished can be found in the Ardour UI.
This leads to the conclusion that we want to differentiate between
varoius degees of severity; some error conditions just can not be
ignored, and must be indicated in an obvious way, e.g. a prominent
nonmodal pop-up to appear for some seconds, while others just warant
an unobstrusive warning sign
the (trivial) implementation turned out to be correct as written,
but it was (again) damn challenging to get the mulithreaded chaotic
test fixture and especially the lambda captures to work correct.
again surprising how such fundamental bugs can hide for years...
Here the reason is that IterAdapter leaves the representation of "NIL" to
its instantiation / users; some users (here in for example the ScopedCollection)
can choose to allow for different representations of "NIL", but the comparison
provided by IterAdapter just compares the embedded pos by face value.
...while tests in the library subdirectory are linked only against
liblumierasupport, which does not provide the multithreading support
In this special case here the actual facility to be tested does not rely
on thread support, only on locking. But the stress test obviously needs
to create several threads. Simple workaround is to move the test into
a test collection linked against all of the application core...
for the simplistic implementation we're using right now this effort might look
exaggerated, but we should consider using a lock-free implementation at some
point in the future, at which point it is good to have a stress test in place
seems like most usages will want to expose this kind of diagnostics for unit testing
and in fact the queue or stack nature is the primary nature of this entity,
while iterability comes as additional trait
- concept for a first preliminary implementation of dispatch into the UI thread
- define an integration effort to build a complete working communication chain
This change was caused by investigation of UI event loop dispatch;
since the GTK UI is designed to run single threaded, any invocation
from other threads need to be diepatched explicitly.
A possible way to achieve this is to use Glib::Dispatcher, which
in turn requires that the current thread (which is in this case the UI thread)
already holds a Glib::MainContext
This prompted me to create a tight link between the external facade interfaces
of the UI and the event loop itself. What remains to be settled is how
to hand over arguments to the action in the main loop
This plugin is essentially an implementation detail, and there is no
mechanism yet to use several different implementations of the interface.
Thus it is pointless to expose the lifecycle methods on a public interface,
while there is no way to obtain an instance of this interface, since the
latter is confined to the internals of the UI subsystem lifecycle
After investigation of current GTK and GIO code, I came to the conclusion
that we do *not* want to rely on the shiny new Gtk::Application, which
provides a lot of additional "convenience" functionality we do neither
need nor want. Most notably, we do not want extended desktop integration
like automatically connecting to D-Bus or exposing application actions
as desktop events.
After stripping away all those optional functions and extensions, it turns
out the basic code to operate the GTK main event loop is quite simple.
This changeset extracts this code from the (deprecated) Gtk::Main and
integrates it directly in Lumiera's UI framework object (UiManager).
this is just a tiny change to make things more othogonal.
Now the unwinding and calls to any GTK / Widget dtors happen *after*
emitting the term signal from UI shutdown. Which means, the other subsystems
are shutting down (in their dedicated threads) as well, thus lowering
the probability of some action still using the UI and triggering an exception
as it turned out, the former functionality was deactivated in 2009
with changeset 6151415
The whole concept seems to be unfinished, and needs to be reworked
and integrated with "Views and Perspectives" (whatever that is...)
See also #1097
