ES 2.0 extensions to match ES3/desktop functionality. The enums from
NV_pack_subimage are not available in gl.xml from Khronos, I would need
to use hardcoded value.
Just added them to the list, nothing integrated or implemented yet. Also
added some more stuff into OpenGL mapping table, as I apparently forgot
some entries.
Useful in this case:
std::optional<Platform::Context> context;
context = Platform::Context{};
This was currently possible only with calling context.emplace(), which
in my opinion is confusing and looks like a no-op. Move assignment is
still not allowed, because having two separate state trackers (and
deleting one of them) currently makes no sense.
It is superseded by core functionality. The only annoyance is that you
need to use TextureFormat::SRGB in ES2 and TextureFormat::SRGB8 in ES3,
but that's with many other formats anyway. Also apparently the unsized
format is still allowed in core desktop GL, which is a shame.
For more clarity it's now better to explicitly list all extensions for
each API even though they might get duplicated. For WebGL they also link
to WebGL spec, which might contain a bit more info.
It doesn't make any sense -- WebGL 2 doesn't provide any equivalent
functionality for this and so I don't even know what values should this
return (3.0? 2.0?). Instead I just check for "WebGL 2" string prefix and
treat it as ES 3.0.
This was the actual problem. Most of ES extensions are not available in
WebGL, thus the GL headers and the code was far more bloated than it
needed to be. The GL header is now reduced and the previous 13 commits
were disabling features that aren't actually available in WebGL.
The final executable size is reduced by ~50 kB, which actually isn't
much, but still something.
Some ES extensions (ANGLE_depth_texture and ANGLE_instanced_arrays) have
now WEBGL_* prefix. I'm still using the original prefix in the
implementation because there are headers for these, but in public docs
and elsewhere they are exposed with WEBGL_*.
In OpenGL ES 2.0 there is EXT_draw_buffers, which I overlooked somehow,
so I added it to extension list and included in the implementation. It
combines NV_draw_buffers and NV_fbo_color_attachments, so the
implementation now selects one of the two based on which extension is
supported, preferring the EXT one. Updated the documentation to be
less confusing, fixed extension links. Also the single-output
mapForDraw() is not handled separately on ES anymore and just calls
DrawBuffers implementation with single parameter, resulting in less
generated code.
EXT_draw_buffers can also be called on default framebuffer and
apparently in ES there is no way to map front framebuffer for drawing,
so I removed it from the DefaultFramebuffer::DrawAttachment enum.
Full support for EXT_transform_feedback, transform feedback objects
from ARB_transform_feedback2 and equivalent OpenGL ES 3.0 functionality.
Example usage is in src/Magnum/Test/TransformFeedbackGLTest.cpp, I'll
add some example later.
According to reports on delphigl.de this extension is far more supported
in comparison to the NV version (and also there's much less FF cruft in
the specification).
In OpenGL ES this is implemented in EXT_multi_draw_arrays extension, if
it is not available, the functionality is emulated using sequence of
normal draw() calls.
Functionality provided by GL 3.3 and ARB_instanced_arrays, on ES2 this
is again implemented in three different extensions --
{ANGLE,EXT,NV}_instanced_arrays. They are disabled until Magnum has
proper extension loading on ES.
On desktop GL this is provided by ARB_draw_instanced (GL 3.1). Base
instance is available only on desktop GL (4.2, ARB_base_instance). In
ES2 the instanced functionality is provided by three (!) different
extensions (ANGLE_instanced_arrays, EXT_draw_instanced,
NV_draw_instanced), the proper implementation is chosen on context
creation based on what extension is available. Though we don't have
extension loader for ES yet, thus all these extensions are disabled and
the implementation has assertion in it.
Added blind test which tests only that something has been drawn and no
errors were emitted, but not whether the right command is used. I'll
probably need to check this later, because the Mesh::draw() behemoth is
going slightly out of hand :)
I didn't yet have time to add more complete support for ES 3.1, but the
engine should at least work on it. If the driver reports ES 3.0 or 3.1
it is taken as valid value in both ES2 and ES3 builds (i.e. the engine
can work in ES2 mode also on ES3 driver).
Vladimír Vondruš