Q:

Mathjax offline quick latex rendering

I would like to have a real time latex renderer, so I can make a youtube video with a screen recorder and a mic, teaching how to solve a math problem, while I type latex, and the screen shows both my latex code and the rendered math in real time while I speak.
I know of Bakoma Tex, it would be the ideal solution, but it is not free and I can't afford it at the time.
The latex rendering from math.stackexchange would fit perfect for my needs.  But I would like to modify the presentation: I would like to make the textarea bigger so that more can be seen at a glance.
The live demo in https://www.mathjax.org/#demo is also almost perfect, but it doesn't make a newline when I press enter.
I modified the example https://docs.mathjax.org/en/v1.0/typeset.html so that the input is a textarea, and the event is onkeyup so that it updates on every key press instead of waiting for me to press enter to render.  But it kind of "blanks" the preview for a second before every keypress.  And it only works in mathmode, so I can't type inline math.
What suggestions do you have to render latex real time for free like this? I would prefer an offline solution, but in principle could use an online solution too. Is this even possible?
Thanks.
PD: Sorry if this isn't the place to post a request like this.

A:

It sounds like you're looking for something like StackEdit, which is free but online (but with open source and permissive licensing, so you could conceivably run your own offline if you wanted).
Alternately, it sounds like you want a LaTeX compiler. For example, when I write LaTeX, I splitscreen and have the source on one half of my screen and the updated pdf on the other half. Then this becomes a question of which LaTeX text editor/IDE to use. Many suggestions are given in 
this question on TeX.se. Note that essentially all of this software is free and offline.
You can get very similar functionality if you use ShareLatex.com, which has a splitscreen LaTeX+rendered output setup by default. This is free, but online.
It is possible for you to configure a MathJax setup to make this work in a way very similar to how MathJax works on Math.SE. However this meta is not the place to ask about that. If you choose this path, you should instead decide on what you want, then read the MathJax documentation (it looks like you've started this). If you have further questions, you can either ask the MathJax developers or create a question on the corresponding programming Q&A site, perhaps StackOverflow.
In the MathJax demo, the typed text is just put in a single <p> html block. So for instance it is possible to force newlines by adding in your own <p>,</p> blocks. You could configure this away

