Implement custom math keyboard for math expression input interactions.

[seanlip]

Is your feature request related to a problem? Please describe.

In math expression contexts, when a student types * in the Android app, the character * is displayed, and similarly for -. However, this causes confusion because students are used to using × and − instead (and in fact this is what they see when entering similar things in the corresponding interaction fields on Oppia Web).

Describe the solution you'd like

The aim of this issue is to show × and − signs instead when a student types the * and - characters. These should be shown in the input box while they are typing their answer (i.e. these are how the characters should appear within the input box itself).

[BenHenning]

I actually took a look at this and it seems that Android does use the correct characters in the represented answer (since the app renders the expression to LaTeX and, as part of that, replaces the characters). I don't think any additional work is needed here.

[seanlip]

@BenHenning To be clear, I'm talking about in the input field just after the student has typed the character (but not yet submitted), rather than in the represented answer after the student has submitted. Could you please confirm that the former is the case?

[BenHenning]

Ah, I didn't realize that's what you mean. Switching out characters from underneath the student is not a trivial task @seanlip and not something I'd want to risk here. FWIW, the Android keyboard already lets you input × and − directly, so I'm also not sure that the same use case is as necessary here.

[seanlip]

OK, yup -- that was what I was referring to in our call. I was surprised that it seemed easy; thanks for looking into this.

I want to check what you mean by "the Android keyboard already lets you input × and − directly", though? The keyboard looks like the standard one. Here is a screenshot that I got from @rt4914 for numeric expression input -- note that there's only a * and no ×. (Which is fine, I just wanted to double-check this because I have put notes in the lessons instructing students to type *.)

[BenHenning]

You need to open up the number keyboard (via ?123) and then another button appears where the caps button shows now with symbols. Opening the symbols will show various math operators include multiplication and division.

[seanlip]

OK, thanks.

As discussed I think the correct long-term solution here is to have a custom math keyboard for numeric expression input that has the multiplication symbol. In the short term we can leave the current behaviour as-is.

[BenHenning]

Given that we don't yet have a tracking issue for the custom math keyboard, let's keep this one open.

I'm moving it out of the MR5 blocker list since the main mitigation (supporting multi-line placeholder hints for text-based interactions) is being implemented as part of #4506).

[seanlip]

Thanks, sounds good. I renamed the issue accordingly.