QuadRender.kt

override fun onSurfaceCreated(gl: GL10?, config: EGLConfig?) {
   // create shader program from the source code
createProgram(vertexShaderSource, fragmentShaderSource)

   // bind vector shader attributes
   inPositionHandle = GLES20.glGetAttribLocation(program, VERTEX_SHADER_IN_POSITION)
   checkGlError("glGetAttribLocation $VERTEX_SHADER_IN_POSITION")
   if (inPositionHandle == UNKNOWN_ATTRIBUTE) throw RuntimeException("Could not get attrib location for $VERTEX_SHADER_IN_POSITION")

   inTextureHandle = GLES20.glGetAttribLocation(program, VERTEX_SHADER_IN_TEXTURE_COORD)
   checkGlError("glGetAttribLocation $VERTEX_SHADER_IN_TEXTURE_COORD")
   if (inTextureHandle == UNKNOWN_ATTRIBUTE) throw RuntimeException("Could not get attrib location for $VERTEX_SHADER_IN_TEXTURE_COORD")

   uMVPMatrixHandle = GLES20.glGetUniformLocation(program, VERTEX_SHADER_UNIFORM_MATRIX_MVP)
   checkGlError("glGetUniformLocation $VERTEX_SHADER_UNIFORM_MATRIX_MVP")
   if (uMVPMatrixHandle == UNKNOWN_ATTRIBUTE) throw RuntimeException("Could not get uniform location for $VERTEX_SHADER_UNIFORM_MATRIX_MVP")

   uSTMatrixHandle = GLES20.glGetUniformLocation(program, VERTEX_SHADER_UNIFORM_MATRIX_STM)
   checkGlError("glGetUniformLocation $VERTEX_SHADER_UNIFORM_MATRIX_STM")
   if (uSTMatrixHandle == UNKNOWN_ATTRIBUTE) throw RuntimeException("Could not get uniform location for $VERTEX_SHADER_UNIFORM_MATRIX_STM")

   // (!) bind attributes for fragment shader
   uMyUniform = GLES30.glGetUniformLocation(program, FRAGMENT_SHADER_UNIFORM_MY_UNIFORM)
   checkGlError("glGetUniformLocation $FRAGMENT_SHADER_UNIFORM_MY_UNIFORM")
   if (uMyUniform == UNKNOWN_ATTRIBUTE) throw RuntimeException("Could not get uniform location for $FRAGMENT_SHADER_UNIFORM_MY_UNIFORM")
}