The caret is invisible after an empty group {}

[timmckague]

Description

The cursor is not visible when focusing (clicking) on a mathfield if the field was initialized with an empty superscript or subscript.

Steps to Reproduce

To reproduce open https://cortexjs.io/mathlive/guides/interacting/

in the "changing content" section, enter the latex "x^{}"

then in the math field, click to right of the x, notice the field is in focus but the cursor does not appear.

Environment

Chrome on OSX

[WildYellowfin]

Can I ask why you're doing this? {} isn't really supposed to happen in general. What is the expected / desired behavior?

[arnog]

Not sure what the use case is in this particular instance, but in general any valid LaTeX should be handled correctly by MathLive.

{} is used in LaTeX as an "empty" atom, which can be used to control spacing ({}-1 vs -1). It can also be used for example in chemistry to have "floating" superscripts, e.g. {}^{12}C to denote the carbon-12 isotope.

[timmckague]

Can I ask why you're doing this? {} isn't really supposed to happen in general. What is the expected / desired behavior?

I have a website that lets people save math expressions and sometimes they enter invalid expressions or expressions that are a work in progress. If they come back later to edit those expressions they might run into this and be confused why a cursor is not appearing. I agree that this is probably not something will happen regularly, but seemed like bug that was worth reporting.

[arnog]

This is now working correctly.

[timmckague]

Thanks for fixing this.