`gst_gl_memory_read_pixels` reads pixels from `GLMemory` into the
pointer, effectively writing to it. This is opposite from
`gst_gl_memory_texsubimage` which reads texture data from `read_pointer`
into `GLMemory`.
Both cases are clarified by changing `read_pointer` to `write_pointer`,
and explaining what `gst_gl_memory_texsubimage` does in addition to
referring back to `gst_gl_memory_read_pixels`.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/806>
Instead of having special cases at each GL texture creation, upload,
readback or copy for all non-8-bits-per-components.
Simply store the more specific format and retrieve the generic
component/type tuple from that.
Introduce a helper function for retrieving the generic GL format (RGBA,
RGB, RG, R, L, A) and type (BYTE, SHORT, SHORT_5_6_5) from a sized
GL format enum (RGBA8, RGB565, RG8, etc).
Except for gst/gl/gstglfuncs.h
It is up to the client app to include these headers.
It is coherent with the fact that gstreamer-gl.pc does not
require any egl.pc/gles.pc. I.e. it is the responsability
of the app to search these headers within its build setup.
For example gstreamer-vaapi includes explicitly EGL/egl.h
and search for it in its configure.ac.
For example with this patch, if an app includes the headers
gst/gl/egl/gstglcontext_egl.h
gst/gl/egl/gstgldisplay_egl.h
gst/gl/egl/gstglmemoryegl.h
it will *no longer* automatically include EGL/egl.h and GLES2/gl2.h.
Which is good because the app might want to use the gstgl api only
without the need to bother about gl headers.
Also added a test: cd tests/check && make libs/gstglheaders.check
https://bugzilla.gnome.org/show_bug.cgi?id=784779
GL_RGB565 is sized internal glformat, the corresponding glformat
should be GL_RGB and type is GL_UNSIGNED_SHORT_565. Otherwise will
return GL_INVALID_ENUM when creating texture.
https://bugzilla.gnome.org/show_bug.cgi?id=783066
Rather than assuming something. e.g. zerocopy on iOS with GLES3 requires
the use of Luminance/Luminance Alpha formats and does not work with
Red/RG textures.
The optimistic download_transfer was not setting the required flag to not
perform glReadPixels on subsequent map (READ). resulting in glReadPixels
happening twice.
GL 2.1 only supports pbo upload.
The wrapped data pointer was only being set on the pbo memory and on the
glmemory so when a download was requested (in GL 2.1), glmemory was
allocating a new data pointer and thus not returning the wrapped data.
The base class is useful for having multiple backing memory types other
than the default. e.g. IOSurface, EGLImage, dmabuf?
The PBO transfer logic is now inside GstGLMemoryPBO which uses GstGLBuffer
to manage the PBO memory.
This also moves the format utility functions into their own file.
