anchor.diff:    }
     return program;
   }
  +
   
   void injectMatrix4(ProgramContext ctx, Matrix4 mat, String sname) {
     var u = ctx.getUniformLocation(sname);
  
positive.code:       _uniforms[v] = b;
      }
      return b;
    }
  }
  
  
negative.code: 
      if (req.beforeAll != null) _beforeAlls.add(req.beforeAll);
      if (req.onAddProgramCtx != null) _onAddProgramCtxs.add(req.onAddProgramCtx);
      if (req.onRemoveProgramCtx != null) _onRemoveProgramCtxs.add(req.onRemoveProgramCtx);
  
      if (req.ctx != null) {
        var isNew = !_ctxs.contains(req.ctx);
  