mesa: misc float-texture fixes
This fixes a few related issues around float-texture support in Mesa:
- We needlessly required support for renderable textures for
OES_texture_float
/OES_texture_half_float
. These extensions only require texturing support. - We didn't check for
EXT_color_buffer_float
; not all hardware supports what's needed for this. - We failed to require
EXT_color_buffer_float
for OpenGL ES 3.2 support - We always allowed
GL_R16F
etc for OpenGL ES 3.0 and above; these requiresEXT_color_buffer_float
-support. - We didn't treat
GL_RGB16F
as color-renderable, as theEXT_color_buffer_half_float
spec requires.
Closes: #10378 (closed)
I've intentionally not added Fixes or other backport tags here, because I'm afraid of feature-regressions in the middle of a stable-branch, which doesn't seem ideal. But I'm not really sure what the right trade-off here is; input very welcome