Placeholders shouldn't be deletable

[bengolds]

Description

If you type in a function that has a placeholder in it, you shouldn't be able to delete the placeholder; you should only be able to type over it. Similarly, if the contents of a function that takes placeholders are deleted, it should return to having a placeholder instead of being empty.

I'd expect this to be default behavior, but having it as an option would also be reasonable.

With placeholders:

Placeholders deleted (looks confusing):

Steps to Reproduce

1. Press the division key or square root key on the default virtual keyboard.
2. Press delete to delete the selected placeholder.

Actual Behavior

The placeholder is deleted, leaving a blank space (or a weird-looking square root symbol for square root).

Expected Behavior

The placeholder stays put until typed over.

Environment

MathLive version: 0.69.8

[manstie]

To add to this, when you replace the placeholders in the MathLive testing playground matrix, the latex becomes {<input>} which creates an invisible depth to the input.