\left[...\right] should get promoted to bmatrix environment, not matrix

[alexprey]

Description

When I'm use matrix bracets and then try to fill content of that, brecets are removed

I'm use following editor instance https://mathlive.io/examples/basic/index.esm.html

Steps to Reproduce

1. Place matrix bracets from keyboard
2. Enter the first value
3. Press Ctrl + , and type new value (the same when I'm use Enter to place a new row in the matrix)

Actual Behavior

Matrix bracets removed from editor

Expected Behavior

Matrix bracets must be in place

Environment

Operating System
[macOS, Windows, iOS. Include the version if possible]

Browser [Safari, Chrome, IE, Firefox, etc...]

[arnog]

I can't figure out how to reproduce this. Could you clarify exactly which keys on the keyboard you are pressing?

[Kydyralin]

According to the reference page of LaTeX operators (wikibooks and mathlive) for the \begin{matrix}...\end{matrix} syntax it's expected to brackets to be not rendered so I think it's not a bug.

[arnog]

Oh, OK... I think I understand this report now. @Kydyralin is correct: \begin{matrix}...\end{matrix} display its content in tabular form, but without fences.

For square brackets use \begin{bmatrix}...\end{bmatrix} and for parentheses use \begin{pmatrix}...\end{pmatrix}

[alexprey]

Ok, sorry for late response. Initially braces was placed in mathlive by virtual keyboard, but when I add a new column or row - braces disappears from input. I'm record gif, please check it for details

[arnog]

Oh, OK, I really got it now. The problem is in the tabular promotion algorithm (when you add a column/row the existing expression gets "promoted" to a tabular environment). It seems like it's getting promoted to a matrix, while in his case it should get promoted to a bmatrix.

[ImGelu]

@arnog any updates on this? I was able to reproduce this bug differently (not sure if it's the same problem, but I thought that commenting here would be a better option than opening a new issue):

1. Insert a pmatrix: \begin{pmatrix}1 & 2 \\ 3 & 4\end{pmatrix}
   
2. Copy the matrix via CTRL+C or via keyboard shortcut
3. Press =
   
4. Paste the previously copied pmatrix
5. So far, the bracets are still visibile
   
6. Insert another =. The bracets disappear.
   

The latex code output (the pmatrix tags are still there, but the bracets are gone): \begin{equation*} \begin{pmatrix}1 & 2 \\ 3 & 4\end{pmatrix}=\begin{pmatrix}1 & 2 \\ 3 & 4\end{pmatrix}= \end{equation*}

Note: this happens only if the editor has been focused the whole time. If you click outside it (thus losing its focus) before step 6, the bracets are stil there.

[arnog]

@ImGelu that's a different issue

[arnog]

Note: right now, no promotion is done at all (regression)

[arnog]

This is now working correctly. Typing [ a followed by alt+Tab will promote the parenthesis to a bmatrix