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A minor ConPTY refactoring: Goodbye VtEngine Edition (#17510)
The idea is that we can translate Console API calls directly to VT at least as well as the current VtEngine setup can. For instance, a call to `SetConsoleCursorPosition` clearly translates directly to a `CUP` escape sequence. Effectively, instead of translating output asynchronously in the renderer thread, we'll do it synchronously right during the Console API call. Most importantly, the this means that any VT output that an application generates will now be given to the terminal unmodified. Aside from reducing our project's complexity quite a bit and opening the path towards various interesting work like sixels, Device Control Strings, buffer snapshotting, synchronized updates, and more, it also improves performance for mixed text output like enwik8.txt in conhost to 1.3-2x and in Windows Terminal via ConPTY to roughly 20x. This adds support for overlapped IO, because now that output cannot be "skipped" anymore (VtEngine worked like a renderer after all) it's become crucial to block conhost as little as possible.⚠️ Intentionally unresolved changes/quirks: * To force a delayed EOL wrap to wrap, `WriteCharsLegacy` emits a `\r\n` if necessary. This breaks text reflow on window resize. We cannot emit ` \r` the way readline does it, because this would overwrite the first column in the next row with a whitespace. The alternative is to read back the affected cell from the buffer and emit that character and its attributes followed by a `\r`. I chose to not do that, because buffer read-back is lossy (= UCS2). Unless the window is resized, the difference is unnoticeable and historically, conhost had no support for buffer reflow anyway. * If `ENABLE_VIRTUAL_TERMINAL_PROCESSING` is set while `DISABLE_NEWLINE_AUTO_RETURN` is reset, we'll blindly replace all LF with CRLF. This may hypothetically break DCS sequences, but it's the only way to do this without parsing the given VT string and thus the only way we can achieve passthrough mode in the future. * `ENABLE_WRAP_AT_EOL_OUTPUT` is translated to `DECAWM`. Between Windows XP and Windows 11 21H2, `ENABLE_WRAP_AT_EOL_OUTPUT` being reset would cause the cursor position to reset to wherever a write started, _if_ the write, including expanded control chars, was less than 100 characters long. If it was longer than that, the cursor position would end up in an effectively random position. After lengthy research I believe that this is a bug introduced in Windows XP and that the original intention was for this mode to be equivalent to `DECAWM`. This is compounded by MSDN's description (emphasis mine): > If this mode is disabled, the **last character** in the row is > overwritten with any subsequent characters.⚠️ Unresolved issues/quirks: * Focus/Unfocus events are injected into the output stream without checking whether the VT output is currently in a ground state. This may break whatever VT sequence is currently ongoing. This is an existing issue. * `VtIo::Writer::WriteInfos` should properly verify the width of each individual character. * Using `SetConsoleActiveScreenBuffer` destroys surrogate pairs and extended (VT) attributes. It could be translated to VT pages in the long term. * Similarly, `ScrollConsoleScreenBuffer` results in the same and could be translated to `DECCRA` and `DECFRA` in the near term. This is important because otherwise `vim` output may loose its extended attributes during scrolling. * Reflowing a long line until it wraps results in the cooked read prompt to be misaligned vertically. * `SCREEN_INFORMATION::s_RemoveScreenBuffer` should trigger a buffer switch similar to `SetConsoleActiveScreenBuffer`. * Translation of `COMMON_LVB_GRID_HORIZONTAL` to `SGR 53` was dropped and may be reintroduced alongside `UNDERSCORE` = `SGR 4`. * Move the `OSC 0 ; P t BEL` sequence to `WriteWindowTitle` and swap the `BEL` with the `ST` (`ESC \`). * PowerShell on Windows 10 ships with PSReadLine 2.0.0-beta2 which emits SGR 37/40 instead of 39/49. This results in black spaces when typing and there's no good way to fix that. * A test is missing that ensures that `FillConsoleOutputCharacterW` results in a `CSI n J` during the PowerShell shim. * A test is missing that ensures that `PtySignal::ClearBuffer` does not result in any VT being generated. Closes #262 Closes #1173 Closes #3016 Closes #4129 Closes #5228 Closes #8698 Closes #12336 Closes #15014 Closes #15888 Closes #16461 Closes #16911 Closes #17151 Closes #17313
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