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-- OpenGL texture id
-- Is Current not freeing texture on disposal?
-- Is texture valid?
-- Tell Current not to free texture on disposal.
-- If you call this, you will be responsible for freeing
-- the OpenGL texture yourself using gl_delete_textures!
-- Save texture in global textures list.
-- A saved texture will not be freed, even when you loose
-- the reference to the texture object. To free it later use
-- the global storage GL_TEXTURES.
-- TODO: maybe a mechanism to add an id would be nice.
Base class for OpenGL texture.
Use id to access the OpenGL texture id.