set uniform and bind texture
set uniform and bind texture
check this is current shader program
glUseProgram, set this is current shader program or set zero (if u==false)
create program, attach shaders, bind attrib locations, link program
makes shaders if are not compiled and attach their
check link status, throw exception if false
uses result of attribLocations() call, affect after link() call
uses result of fragDataLocations() call, affect after link() call
link program and check status