anchor.diff:        if (req.before != null) req.ctx._befores.add(req.before);
         if (req.at != null) req.ctx._ats.add(req.at);
         if (isNew) {
  -        _autoData.forEach((k,v) {
  -          if (req.ctx.getUniformLocation(k) != null) {
  -            req.ctx._befores.add(v);
  -          }
  -        });
           _onAddProgramCtxs.forEach((f)=> f(this, req.ctx));
         }
       } else {
  
positive.code:   return shader;
  }
  
  _linkProgram(RenderingContext gl, Shader vertex, Shader fragment, [deleteShaderOnFailure = true]) {
    var program = gl.createProgram();
    gl.attachShader(program, vertex);
  
negative.code:   return program;
  }
  
  void injectMatrix4(ProgramContext ctx, Matrix4 mat, String sname) {
    var u = ctx.getUniformLocation(sname);
    if (u != null) {
  