I have an ES 2.0 app and would like to use ETC2 texture compression if it is available (i.e. I am running on a device that supports ES 3.0 standard). Is it possible to use ETC2 in ES 1.1/2.0, and if so how can I query if a device supports it? For most forms of texture compression, there is an extension I can query for, but there is no extension for ETC2 since it is built in.
There are a bunch of GL extensions related to ETC2 support:
OES_compressed_ETC2_RGB8_texture OES_compressed_ETC2_sRGB8_texture OES_compressed_ETC2_punchthroughA_RGBA8_texture OES_compressed_ETC2_punchthroughA_sRGB8_alpha_texture OES_compressed_ETC2_RGBA8_texture OES_compressed_ETC2_sRGB8_alpha8_texture
The ES3 compatibility extension aggregates those (and a few others). You can query for these extensions to check support, presumably.