[Proposal] Add support for automatically switching text input to RTL or LTR based on first character typed

[sm2017]

Use case

In multilingual text fields, Bidirectional text input is automatically recognised. For example, typing ب as the first character in Whatsapp places the cursor the right side and typing b as the first, places the cursor at the left side. That is it automatically detects the language and makes the text input appropriate, whether it is an RTL or LTR language.

Proposal

I think flutter must detect bidirectional text input out of the box, no matter what is the current Directionality.of(context). The same behaviour stated above should be exhibited in flutter textfields.

[sm2017]

Not only TextField, but also Text must detect bidirectional text out of the box, I think having a bool property like matchContentDirection with default value as true is awesome, I'm not sure may be TextAlign.auto as default text direction is better
Detecting bidirectional text must be added to TextField itself and all text in it like hint , helper, error

[danagbemava-nc]

In multilingual text input, usually it detect Bidirectional text

Hi @sm2017, I'm not particularly familiar with Bidirectional text input, can you expand more on this?

[sm2017]

See https://en.m.wikipedia.org/wiki/Bidirectional_text

There is a bidi class in flutter https://api.flutter.dev/flutter/intl/Bidi-class.html

It is impossible to implement my feature request in application layer, because we have dependencies that has text field or text widget

[danagbemava-nc]

@sm2017, my question was poorly phrased, what I meant was can you expand a bit more on this statement you made earlier?

In multilingual text input, usually it detect Bidirectional text

[sm2017]

Let me describe default behavior of text input in Android os, Chrome, Whatsapp and ...

In your Chrome search bar, try to type ب , feel free to copy and paste it, you can see the direction of text is detected as LRT, AFAIK it's a common behavior in most operation systems and applications

It's Bidirectional text input as it's context-aware

[danagbemava-nc]

@sm2017, thanks for the insight.
I have updated the proposal to make it clearer.

[TarekkMA]

It might be a good idea to add a new value called auto similar to the web.

For reference here are the docs on dir.
https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/dir

[xmine64]

I need this, it's so useful. I added some code to onChange property of TextFields in my app to set text direction based on content.

[LongCatIsLooong]

@goderbauer This seems technically feasible (https://unicode-org.github.io/icu-docs/apidoc/dev/icu4c/ubidi_8h.html#a165ae276878c7a54fd8b067db0d12f40).

Does it make sense to add this to TextPainter? I guess for WidgetSpans we'll need a new low-level API that gives us the real writing direction of a paragraph, before we can build those inline widgets with the correct writing directions?