... grouping the channels; rather than one flat vector.
OGG, GStreamer and FFmpeg import were written to allow multiple multi-channel
tracks; others always imported one group of channels.
All of that is reflected in the results returned by the importers, though it
makes no difference yet in AudacityProject::AddImportedTracks (where the
results are used).
We were for example getting many of these:
\audacity\src\widgets\numerictextctrl.h(171): warning C4458: declaration of 'value' hides class member
MSVC2013 didn't warn about these, but MSVC2017 does.
... and similar wx "variadics," which all treat wxString smartly enough that
you don't need this.
Don't need c_str either to convert wxString to const wxChar * because
wxString has a conversion operator that does the same.
... This means unneeded block files can be reclaimed sooner.
This also eliminates the checks of use_count, which might vary in a
multithreaded context; though that didn't really matter (because once it
was below 2, the function had the only remaining shared_ptr to the block file,
so it could not have increased again to 2).
... whenever they really describe the size of a buffer that fits in memory, or
of a block file (which is never now more than a megabyte and so could be fit in
memory all at once), or a part thereof.
... with run-time assertions.
I examined each place and reasoned that the narrowing was safe, and commented
why so.
Again, there are places where the sampleCount variable will later be changed
to have a different type, and they are not changed here.
... A non-narrowing conversion out to long long is a necessity, but the
conversions to float and double are simply conveniences.
Conversion from floating is explicit, to avoid unintended consequences with
arithmetic operators, when later sampleCount ceases to be an alias for an
integral type.
Some conversions are not made explicit, where I expect to change the type of
the variable later to have mere size_t width.
... Define lots of operators for disambiguation, but they will go away after
all conversions from sampleCount to built-in numerical types are forced
to be explicit.
... And in some places where a library uses signed types, assert that
the reported number is not negative.
What led me to this, is that there are many places where a size_t value for
an allocation is the product of a number of channels and some other number.
... This makes much code agnostic about how other things (functions and
arguments) are typed.
Many of these neeed to become size_t instead of sampleCount.
