Enable `Alt+x` to type in Unicode characters

[SteveL-MSFT]

Prerequisites

• Write a descriptive title.

Description of the new feature/enhancement

Per https://support.microsoft.com/en-us/office/insert-ascii-or-unicode-latin-based-symbols-and-characters-d13f58d3-7bcb-44a7-a4d5-972ee12e50e0 it's expected in Windows to type a Unicode character to type the numbers, then Alt+x will transform it into a Unicode char. So:

0024<Alt+x>

Should result in:

$

Although this is a Windows thing, I don't see any reason it shouldn't work by default on Linux, macOS.

Proposed technical implementation details (optional)

Enable a default keybinding (it doesn't appear Alt+x is bound by default) to look at the last 4 characters and if they are a numbers that result in a valid unicode character, replace them with the Unicode character and move the cursor.

[sba923]

Per https://support.microsoft.com/en-us/office/insert-ascii-or-unicode-latin-based-symbols-and-characters-d13f58d3-7bcb-44a7-a4d5-972ee12e50e0 it's expected in Windows to type a Unicode character to type the numbers, then Alt+x will transform it into a Unicode char. [...]
Although this is a Windows thing, I don't see any reason it shouldn't work by default on Linux, macOS.

My understanding is that it is an Office thing, not a Windows thing. Do you know of any non-Office context where this actually works?

[SeeminglyScience]

Proof of concept:

Set-PSReadLineKeyHandler -Chord 'alt+x' -ScriptBlock {
    $buffer = $null
    $cursor = 0
    [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState([ref] $buffer, [ref] $cursor)
    if ($cursor -lt 4) {
        return
    }

    $number = 0
    $isNumber = [int]::TryParse(
        $buffer.Substring($cursor - 4, 4),
        [System.Globalization.NumberStyles]::AllowHexSpecifier,
        $null,
        [ref] $number)

    if (-not $isNumber) {
        return
    }

    [Microsoft.PowerShell.PSConsoleReadLine]::Delete($cursor - 4, 4)
    [Microsoft.PowerShell.PSConsoleReadLine]::Insert([char]::ConvertFromUtf32($number))
}

Could also just be added to the example profile rather than as a built-in shortcut

🎉 This issue was addressed in 3652, which has now been successfully released in v2.3.1-beta1. 🎉

[sba923]

Here's a modified version that supports 4-, 5- and 6-character hex values:

	# modified to support 6- to 4-character hex values
	Set-PSReadLineKeyHandler -Chord 'Alt+x' `
		-BriefDescription ToUnicodeChar `
		-LongDescription "Transform Unicode code point into a UTF-16 encoded string" `
		-ScriptBlock {
		$buffer = $null
		$cursor = 0
		$length = 6
		$minlength = 4
		[Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState([ref] $buffer, [ref] $cursor)

		while ($true)
		{
			if ($cursor -ge $length)
			{
				$number = 0
				$isNumber = [int]::TryParse(
					$buffer.Substring($cursor - $length, $length),
					[System.Globalization.NumberStyles]::AllowHexSpecifier,
					$null,
					[ref] $number)
			}
			else
			{
				$isNumber = $false
			}

			if ($isNumber)
			{
				break
			}

			if ($length -eq $minlength)
			{
				return
			}
			
			$length--
		}



		try
		{
			$unicode = [char]::ConvertFromUtf32($number)
		}
		catch
		{
			return
		}

		[Microsoft.PowerShell.PSConsoleReadLine]::Replace($cursor - $length, $length, $unicode)
	}