Breaking changes! Boxes and Editor

[JerryI]

It was a long path starting from denying Mathematica's Boxes to using them everywhere.
Before, anything related to "2D Math input" was an odd combination of editor's tokens and WL expressions syntax. For example

In the editor's input field it looks like

CM6Fraction[2 x, CM6Sqrt[\[Pi]]]-CM6Fraction[2 CM6Superscript[x, 3], 3 CM6Sqrt[\[Pi]]]

There are many problems with that

• editor has to parse all WL expressions recursively counting {, [ (slow and unreliable!)
• not compatible with non-WLJS editors and hard to read if copied to outside of WLJS ecosystem
• each time each change causes recreation of the whole CM6Fraction or other (my bad in implementation). It means when the expression gets bigger it slows down frontend, especially big matrixes

In principle to maintain such syntax-sugar, one need to give to the editor some hints and markers, that shows what and where should be transformed. The safest way is to use WL comments.

Now the same expression will look like this

(*FB[*)((2 x)(*,*)/(*,*)((*SqB[*)Sqrt[\[Pi]](*]SqB*)))(*]FB*)-(*FB[*)((2 ((*SpB[*)Power[x(*|*),(*|*)3](*]SpB*)))(*,*)/(*,*)(3 ((*SqB[*)Sqrt[\[Pi]](*]SqB*))))(*]FB*)

It does look more complicated, but if you just remove all comments

((2 x)/(Sqrt[\[Pi]]))-((2 (Power[x,3]))/(3 (Sqrt[\[Pi]])))

• you can copy your cell's text to any WL parsers, use it with wolframscript with no changes made!
• it does not affect the code structure
• it has all markers for the editor (no need to parse WL on client's side!), that makes all process of writing equations much safer

It has a big impact on the performance, especially while working with matrixes. InterpretationBox and other sweet tools are supported in a similar way using comments.

The previous notations like CM6Fraction and etc are still supported in Kernel, but they will not be drawn in the editor.

Hope it will improve your experience with 2D Math input.

Cheers,
Kirill