Some of these checks became pointless after dropping ES 2.0 support for
extended filtering.
GL_EXT_texture_rg is part of core in ES 3.0, and we already check for
this version, so testing for the extension is redundant.
GL_OES_texture_half_float_linear is also always available, at least as
far as our needs go.
The functionality we need from GL_EXT_color_buffer_half_float is always
available in ES 3.2, and we explicitly check for ES 3.2, so reject this
extension if the ES version is new enough.
ES 2.0 has this weird rule that not the internalformat parameter
determines the internal format, but the combination of all texture
parameters. GL_OES_texture_half_float thus does not specify e.g. a
GL_RGBA16F format, but requires passing GL_RGBA as format and
GL_HALF_FLOAT_OES as type. We won't bother with this, since ES 2.0 is a
lost cause anyway.
This also removes the OpenGL error when the code is trying to create a
f16 FBO for testing whether FBOs work.
Only a few very low bit depth internal formats can be rendered to in
pure ES2 (GL_RGB565 is the "best" one).
Seems like the only potentially reasonable renderable formats in ES2
could be provided via GL_OES_rgb8_rgba8, or half-floats, so don't
bother with this at all.
This merges all knowledge about texture format into a central table.
Most of the work done here is actually identifying which formats exactly
are supported by OpenGL(ES) under which circumstances, and keeping this
information in the format table in a somewhat declarative way. (Although
only to the extend needed by mpv.) In particular, ES and float formats
are a horrible mess.
Again this is a big refactor that might cause regression on "obscure"
configurations.
wm4