Originally I copied this over from SceneGraph template classes, where it
was used to prevent the compiler from needlessly instantiating a
template that was already available elsewhere. But this is a different
case, the extern template is not preventing any instatiation of
anything, no code is inline, so it apparently should not have been there
at all, instead of being disabled for ḾinGW GCC and clang-cl, and then
subsequently discovering it also breaks MinGW Clang.
Since I'm not testing with MinGW Clang on the CI (only with MinGW GCC),
this went unnoticed for a while -- sorry.
It's more useful if the Error class is directly referenced than saying
just "error output" -- so people can grab it, redirect it, etc. Also
drop the useless "does what it is expected to do on success" sentences
that add no value whatsoever.
Except for file callbacks, for these I have another change planned for
zero-copy import and it would be unwise to break stuff twice, providing
two sets of backwards compatibility wrappers. The image / scene
converter plugins went through a similar change earlier already and the
shader converters were made sane since the very beginning. OTOH audio
importers and text stuff are scheduled for merging with Trade or a
larger rework anyway, so I didn't see any point in updating those.
It's mostly a trivial change, except that returned String instances are
now also checked for non-default deleters same as Arrays because yes,
wow such flexibility compared to STL strings. Same was done for
ShaderTools::AbstractConverter already anyway, so nothing unheard-of
either.
The importer plugin interface version is bumped as this likely breaks
ABI in a nasty way that would lead to crashes.
I wanted to avoid including extra stuff with the Manager.hpp split, but
this would make it even worse than having Array and String included
unconditionally. Fortunately it's enough to simply not even have the
declaration.
Same as with MeshData2D/3D, the original ObjectData API and plugin
interfaces are preserved to keep existing code as well as existing
importer implementations working. As Magnum's own importers will get
updated to the new SceneData workflow, a backward compatibility layer
provided that translates it to the subset that the legacy ObjectData
understands.
With this commit, both existing plugin code can build (and test against)
the new workflow, and any ports to the new workflow can test against the
legacy interfaces. Except that for now the compatibility layer doesn't
deal with objects that have more than one mesh or for example a light
and a camera attached, this will be done in a separate step.
Using openMemory() instead of openData() allows the implementation to
assume the data will stay in scope for as long as needed, which can
prevent unnecessary copies in some plugin implementations.
It warranted a new flag, DataFlag::ExternallyOwned, to describe this
kind of memory. I couldn't reuse Owned as that's used for allocations
owned by the instance, which is too little for certain future use cases.
For example returning *Data instances referencing an Owned memory would
mean the user has to assume the memory is gone when the importer
instance is gone, and that's generally not true for memory passed to
openMemory().
Originally I thought I would do this later, but then realized the
existing plugin implementations would need to get all updated again to
be aware of the new flag, with some being forgotten, and it's just
easier to do the whole thing in a single step.
This makes it much less annoying to pass arbitrarily typed data, such as
std::uint8_t or char8_t and what not. It was already done like this for
the new shader converter plugins, where the input is often 32-bit ints
for SPIR-V.
OTOH the internal virtual API is kept with ArrayView<const char>, as
that makes it easier to operate on by the implementations.
This allows to better describe memory ownership and transfer it instead
of forcing the plugins to allocate their own local copy if the import
happens in-place on the imported data. Right now that's mainly for the
openFile() use case, which implicitly allocated an Array with file
contents only to pass it to openData() which then made a copy because it
could not make any assumption about data scope.
In other words, certain plugins (TgaImporter, KtxImporter, DdsImporter,
CgltfImporter and possibly others) will now have their peak memory usage
*halved*.
Interestingly enough, there were no docs whatsoever for image and scene
conversion, and neither it was mentioned what all scene data can be
imported. Sigh.
There will be Flag::FlipY for images at some point, enabled by default
for compatibility with existing GL code, and so it makes sense to start
discouraging setFlags() as early as possible to avoid people resetting
the default by accident.
Also update the imageconverter, sceneconverter and shaderconverter utils
to use these instead of setFlags().
Makes more sense as the function isn't expected to fail (and thus any
kind of lazy population is not possible as it would be too late for
error checks anyway).
*Not* updating interface strings even though this is an ABI break
because we're doing that right after the skin import interface bump.
The plugin interface version got bumped to avoid ABI issues when loading
plugins that weren't updated for the change, but apart from that this
shouldn't be a breaking change, as the API returns a type that can be
both an Optional and a Pointer.
Similar to image mip level import, but this is largely left to be
importer-specific. For example PLY defines per-face data and sometimes
one might want to import them as-is, without them being turned into a
per-vertex property.
Vladimír Vondruš