The rendering of the safety-critical application was written completely in C using OpelGLSC (https://www.khronos.org/openglsc/) to render the GUI, and had to pass a formal validation suite (MISRA was the big one IIRC). Simply put, the safety critical application essentially was not allowed to "fail in an unsafe manner" in the DO-178 sense. Using javascript, or some c++ gui library was very much out of the question.
Fortunately, this was not an airborne platform, so failing safely was much simpler than what a true aviation stack or medical stack would need to do.
The rendering of the safety-critical application was written completely in C using OpelGLSC (https://www.khronos.org/openglsc/) to render the GUI, and had to pass a formal validation suite (MISRA was the big one IIRC). Simply put, the safety critical application essentially was not allowed to "fail in an unsafe manner" in the DO-178 sense. Using javascript, or some c++ gui library was very much out of the question.
Fortunately, this was not an airborne platform, so failing safely was much simpler than what a true aviation stack or medical stack would need to do.