browsers do the following: By given set of HTML and CSS produce bitmap on screen. That's perfectly determined task (modulo browser differences). WYSIWYG edito

browsers do the following: By given set of HTML and CSS produce bitmap on screen. That's perfectly determined task (modulo browser differences). WYSIWYG editor does the opposite task: With the given bitmap on screen produce set of valid HTML and CSS declarations. The last task is undetermined mathematically speaking - with modern HTML and especially CSS there are too many ways of get the same rendering using completely different CSS tricks - absolute positioning, floats, display:grid and flexbox etc. etc.