Ctrl+Backspace works, and two other small fixes

[mkitzan]

Summary of the Pull Request

Changes the Ctrl+Backspace input sequence and how it is processed by InputStateMachineEngine. Now Ctrl+Backspace deletes a whole word at a time (tested on WSL, CMD, and PS).

PR also fixes two other issues which just needed some someone to implement them.

References

PR Checklist

• Closes Ctrl-backspace does not delete back to the previous wordbreak #755, Sending negative values to ResizePseudoConsole returns S_OK #3447, Trying to define color 256 causes temporary hang #3720
• CLA signed. If not, go over here and sign the CLA
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: Ctrl-backspace does not delete back to the previous wordbreak #755

Detailed Description of the Pull Request / Additional comments

Changed the input sequence for Ctrl+Backspace to \x1b\x8 so the sequence would pass through _DoControlCharacter. Changed _DoControlCharacter to process \b in a way which forms the correct INPUT_RECORDs to delete whole words.

Fixed #3447 by verifying that COORD X,Y values are positive.
Fixed #3720 by wrapping the at call in a try-catch.

Validation Steps Performed

Ctrl+Backspace works 🎉
Can no longer repro #3720

[DHowett-MSFT]

NAK on combining these three different bug fixes into one pull request -- sorry! We find ourselves bisecting fairly often, and it makes it a lot easier to reason about when each change is fairly pure.

For the future, though: github only works "properly" if you repeat the word closes. Closes #x, closes #y, closes #z. 😄

[DHowett-MSFT]

(also, thank for you doing this: I appreciate how willing you are to jump into things and deal with our somewhat opaque (at times) review requirements!)

[mkitzan]

No problem. I'll reopen separate ones for each.

[mkitzan]

For the future, though: github only works "properly" if you repeat the word closes. Closes #x, closes #y, closes #z. 😄

If that's the case then issue #2248 should be closed because of this PR.

[DHowett-MSFT]

Oh dang, excellent catch! Thanks!

[JakeShirley]

Note: I am only looking at this because I am invested in the ctrl+backspace functionality, I have no idea what coding standards are going on here.

You should probably nix the exception handling and use _colorTable.find like this:

auto colorTableItr = _colorTable.find(tableIndex);
if (colorTableItr != _colorTable.end()) {
  *colorTableItr  = dwColor;
  ...
}
else {
  return false;
}

[mkitzan]

_colorTable is a std::array which doesn't have a find function. Would be an clean way if it did support find though.

[JakeShirley]

Ah, in that case you could std::find(_colorTable.begin(), _colorTable.end(), tableIndex)! (it just does a linear search)

[mkitzan]

Sticking with random access+exception makes the most sense for this function. Calling it with an invalid value is an exceptional event which requires some really arcane input to repro.