Triple clicking in an Entry widget should select all text

[dweymouth]

Checklist

• I have searched the issue tracker for open issues that relate to the same feature, before opening a new one.
• This issue only relates to a single feature. I will open new issues for any other features.

Is your feature request related to a problem?

This is fairly standard behavior across OSes and UI toolkits. We should aim to support it.

Is it possible to construct a solution with the existing API?

Yes, by extending Entry to override Tapped and implementing the behavior yourself

Describe the solution you'd like to see.

Triple clicking in the entry should select all text in a single line entry, or all of the current line in a multi-line entry

[andydotxyz]

Yeah this is good. I'm not sure if we need to do this with actual triple click implementation or through baking it in to just Entry?

[dweymouth]

I think baking it into entry is probably fine. 99% of widgets won't need a triple click interaction

[dweymouth]

Added on develop