Mark ESC as handled so that it doesn't come back in CharacterHandler

[DHowett]

Fixes #1295.

Summary of the Pull Request

There are four places where we could possibly fix this.

1. mark it handled manually in KeyDownHandler (like Tab)
2. "handle it manually" in TerminalCore (like Ctrl+Space and friends)
3. ignore it in CharacterHandler (like Bksp and Del)
4. "handle it automatically" in TerminalCore by removing it from TerminalInput
   • i cannot figure out why it's in there -- it's in the keypad numeric and keypad application mappings, but it doesn't actually get remapped?

terminal/src/terminal/input/terminalInput.cpp

Line 55 in fad7638

{ VK_ESCAPE, L"\x1b" },

terminal/src/terminal/input/terminalInput.cpp

Line 88 in fad7638

{ VK_ESCAPE, L"\x1b" },

I just chose one. Why not here? We should document what each of those does and why they are they way they are.

PR Checklist

• Closes <ESC> comes through as <ESC><ESC> #1295
• I work here
• I have not yet added tests, so the box to the left is as empty as can be

[DHowett-MSFT]

terminal/src/cascadia/TerminalCore/Terminal.cpp

Lines 265 to 268 in fad7638

	const bool manuallyHandled = ch != UNICODE_NULL;
	const bool translated = _terminalInput->HandleKey(&keyEv);
	return translated && manuallyHandled;

Follow up: why do we need to track manuallyHandled at all in TerminalCore's input translator? It was handled if and only if TerminalInput said it was; if we ever second-guess it, we risk double-sending something.

I guess we want to mark "manually handled" things that TerminalInput won't handle? But then we just won't send the character at all. Hmm.

[DHowett-MSFT]

I see. It's because when we have a character-producing key, it comes in as UNICODE_NULL because we synthesized the key event out of thin air oh my word

[zadjii-msft]

Seems fine to me.

[miniksa]

OK.

[DHowett-MSFT]

gfdi github's merge conflict resolver changed the line endings

[ghost]

🎉Windows Terminal Preview v0.3.2142.0 has been released which incorporates this pull request.:tada:

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