Uno: [Android] When you insert a special character in a TextBox with a Mask, the cursor goes to the left 1 position

[carlh98]

Current behavior

In Android, when you insert a special character (ex: +, -, *, .) in a TextBox (the TextBox/mask needs to not be full/complete).
Ex: Mask is (00000)

• you have entered 123 and you try to add a special character, the cursor will go to the left for 1 position
• the TextBox is empty and you try to add a special character, the first parenthesis of the mask will appear
• you have entered 12345 and you try to add a special character, the second parenthesis of the mask will appear

The TextBox needs to have InputScope="TelephoneNumber"

When the mask is not full, you try to add a special character and the cursor moves to the left

Expected behavior

When the mask is not full, you try to add a special character and the TextBox stays at the same position

How to reproduce it (as minimally and precisely as possible)

Add a special character with the pad to the TextBox and the cursor will move one position to the left

Use the following sample: TextBoxFormattingSample.zip

Environment

Nuget Package:

Uno.UI = 2.0.512-dev.3599
Umbrella.View = 3.8.0-dev.414

Package Version(s):

Affected platform(s):

• [ ] iOS
• [x] Android
• [ ] WebAssembly
• [ ] WebAssembly renderers for Xamarin.Forms
• [ ] Windows
• [ ] Build tasks
• [ ] Solution Templates

Visual Studio:

• [ ] 2017 (version: )
• [ ] 2019 (version: )
• [ ] for Mac (version: )

Relevant plugins:

• [ ] Resharper (version: )

Anything else we need to know?

https://dev.azure.com/nventive/Umbrella/_workitems/edit/164249

[jeromelaban]

Why was this issue closed ? Was it fixed ?

[carlh98]

I've changed the InputScope from Number to TelephoneNumber and the issue of flickering has stopped.
There's now an issue with the cursor moving left but it's related to Umbrella.

[XiaotianNetlift]

This issue can remain closed. The root cause is that the FormattingTextBoxBehavior, which not part of Uno.UI, simply re-adjusts cursor position based on the delta in text length, regardless of the modification(s) occurred before or after the cursor position:

var selectionStart = textbox.SelectionStart;
if (textbox.Text.Length > formattedText.Length) // Non-considered special chars were removed.
{
  selectionStart -= textbox.Text.Length - formattedText.Length;
}
else // String format chars were added.
{
  selectionStart += GetAddedFormattingCharacterCount(textbox);
}

-- https://nventive.visualstudio.com/Umbrella/_workitems/edit/164249/

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