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.
For example if we're looking for a 2D image named "cubemap", the
importer will tell us there's 0 2D images, making a potential mistake
(2D vs 3D) more obvious.
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*.
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.
For backwards compatibility these will delegate to the new MeshData
interfaces for 3D (and nothing for 2D, because so far there were no 2D
scene importers).
Bloaty says it saved 10 kB in Debug build of MagnumGL:
VM SIZE FILE SIZE
-------------- --------------
[ = ] 0 .debug_info +1.59Ki +0.0%
+0.4% +1.50Ki .text +1.50Ki +0.4%
[ = ] 0 .debug_str +409 +0.0%
[ = ] 0 .debug_line +276 +0.1%
[ = ] 0 .debug_abbrev +20 +0.0%
-28.6% -2 [LOAD [RX]] -2 -28.6%
[ = ] 0 [Unmapped] -4.28Ki -41.0%
-22.7% -9.23Ki .rodata -9.23Ki -22.7%
-0.8% -7.73Ki TOTAL -9.73Ki -0.1%
And 4 kB in Release:
VM SIZE FILE SIZE
-------------- --------------
+1.1% +3.44Ki .text +3.44Ki +1.1%
+1.7% +1.39Ki .eh_frame +1.39Ki +1.7%
[ = ] 0 [Unmapped] +656 +51%
-25.5% -9.47Ki .rodata -9.47Ki -25.5%
-0.7% -4.64Ki TOTAL -4.00Ki -0.4%
That's not negative, so I guess that's good. This change is of course
more significant in the context of a minimal WebGL build, where the exe
can be as little as 50 kB -- there 4 kB is almost 10% of the size.
This makes it possible to:
- finally use Magnum as a CMake subproject on Windows and have your
executables not fail to run with a "DLL missing" error (and the
setting is put to cache so superprojects just implicitly make use of
that)
- run tests on Windows without having to install first
- use dynamic plugins from a CMake subproject on any platform without
having to install first or load them by filename --- and the plugin
directory is now easily discovered as relative to
libraryLocation() of the library implementing given plugin interface
It'll get used outside of the root namespace and since the callbacks tend
to be quite complex, it would be silly to require users to implement one
callback for Trade, one for Text and one for Audio, for example.
The original implementation had a few problems:
- If a file callback was set, openFile() was unconditionally calling
right into doOpenData(), making it impossible for the importer to
know the original path for correctly supplying paths to additional
files. Now, if the importer supports Feature::FileCallback,
doOpenFile() is always called. It's also possible for the importer to
save the path and then just delegate to the base doOpenFile()
implementation -- it will handle the file callbacks correctly too.
- If the importer supported neither FileCallback nor OpenData and
callbacks were set, the original doOpenFile() implementation was
called without any warning or anything, doing silently a bad thing.
Now in this case setFileCallbacks() asserts -- programmer has to
check for feature support first.
- It was not possible for the file callback to indicate file opening
failure -- in general, empty files are valid, so a nullptr ArrayView
is also a valid file. Now the callback return an Optional instead.
Vladimír Vondruš