Move cursor in conpty correctly after a backspace when we've delayed an EOL wrap #4403
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…ly, esp conhost v wt v gnome-terminal. Remove ambiguity - just hardcore move the cursor in this scenario.
…avior quite right
…inal behavior quite right" This reverts commit 0a98cce.
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Does this fix the version of #3277 that came back |
Haven't the faintest clue. I'd probably doubt it, do we have a consistent repro for that one? |
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…-actually-did-it-this-time # Conflicts: # src/cascadia/UnitTests_TerminalCore/ConptyRoundtripTests.cpp
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## Summary of the Pull Request Changes how conpty emits text to preserve line-wrap state, and additionally adds rudimentary support to the Windows Terminal for wrapped lines. ## References * Does _not_ fix (!) #3088, but that might be lower down in conhost. This makes wt behave like conhost, so at least there's that * Still needs a proper deferred EOL wrap implementation in #780, which is left as a todo * #4200 is the mega bucket with all this work * MSFT:16485846 was the first attempt at this task, which caused the regression MSFT:18123777 so we backed it out. * #4403 - I made sure this worked with that PR before I even sent #4403 ## PR Checklist * [x] Closes #405 * [x] Closes #3367 * [x] I work here * [x] Tests added/passed * [n/a] Requires documentation to be updated ## Detailed Description of the Pull Request / Additional comments I started with the following implementation: When conpty is about to write the last column, note that we wrapped this line here. If the next character the vt renderer is told to paint get is supposed to be at the start of the following line, then we know that the previous line had wrapped, so we _won't_ emit the usual `\r\n` here, and we'll just continue emitting text. However, this isn't _exactly_ right - if someone fills the row _exactly_ with text, the information that's available to the vt renderer isn't enough to know for sure if this line broke or not. It is possible for the client to write a full line of text, with a `\n` at the end, to manually break the line. So, I had to also add the `lineWrapped` param to the `IRenderEngine` interface, which is about half the files in this changelist. ## Validation Steps Performed * Ran tests * Checked how the Windows Terminal behaves with these changes * Made sure that conhost/inception and gnome-terminal both act as you'd expect with wrapped lines from conpty
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This PR adds support for "Resize with Reflow" to the Terminal. In conhost, `ResizeWithReflow` is the function that's responsible for reflowing wrapped lines of text as the buffer gets resized. Now that #4415 has merged, we can also implement this in the Terminal. Now, when the Terminal is resized, it will reflow the lines of it's buffer in the same way that conhost does. This means, the terminal will no longer chop off the ends of lines as the buffer is too small to represent them. As a happy side effect of this PR, it also fixed #3490. This was a bug that plagued me during the investigation into this functionality. The original #3490 PR, #4354, tried to fix this bug with some heavy conpty changes. Turns out, that only made things worse, and far more complicated. When I really got to thinking about it, I realized "conhost can handle this right, why can't the Terminal?". Turns out, by adding resize with reflow, I was also able to fix this at the same time. Conhost does a little bit of math after reflowing to attempt to keep the viewport in the same relative place after a reflow. By re-using that logic in the Terminal, I was able to fix #3490. I also included that big ole test from #3490, because everyone likes adding 60 test cases in a PR. ## References * #4200 - this scenario * #405/#4415 - conpty emits wrapped lines, which was needed for this PR * #4403 - delayed EOL wrapping via conpty, which was also needed for this * #4354 - we don't speak of this PR anymore ## PR Checklist * [x] Closes #1465 * [x] Closes #3490 * [x] Closes #4771 * [x] Tests added/passed ## EDIT: Changes to this PR on 5 March 2020 I learned more since my original version of this PR. I wrote that in January, and despite my notes that say it was totally working, it _really_ wasn't. Part of the hard problem, as mentioned in #3490, is that the Terminal might request a resize to (W, H-1), and while conpty is preparing that frame, or before the terminal has received that frame, the Terminal resizes to (W, H-2). Now, there aren't enough lines in the terminal buffer to catch all the lines that conpty is about to emit. When that happens, lines get duplicated in the buffer. From a UX perspective, this certainly looks a lot worse than a couple lost lines. It looks like utter chaos. So I've introduced a new mode to conpty to try and counteract this behavior. This behavior I'm calling "quirky resize". The **TL;DR** of quirky resize mode is that conpty won't emit the entire buffer on a resize, and will trust that the terminal is prepared to reflow it's buffer on it's own. This will enable the quirky resize behavior for applications that are prepared for it. The "quirky resize" is "don't `InvalidateAll` when the terminal resizes". This is added as a quirk as to not regress other terminal applications that aren't prepared for this behavior (gnome-terminal, conhost in particular). For those kinds of terminals, when the buffer is resized, it's just going to lose lines. That's what currently happens for them. When the quirk is enabled, conpty won't repaint the entire buffer. This gets around the "duplicated lines" issue that requesting multiple resizes in a row can cause. However, for these terminals that are unprepared, the conpty cursor might end up in the wrong position after a quirky resize. The case in point is maximizing the terminal. For maximizing (height->50) from a buffer that's 30 lines tall, with the cursor on y=30, this is what happens: * With the quirk disabled, conpty reprints the entire buffer. This is 60 lines that get printed. This ends up blowing away about 20 lines of scrollback history, as the terminal app would have tried to keep the text pinned to the bottom of the window. The term. app moved the viewport up 20 lines, and then the 50 lines of conpty output (30 lines of text, and 20 blank lines at the bottom) overwrote the lines from the scrollback. This is bad, but not immediately obvious, and is **what currently happens**. * With the quirk enabled, conpty doesn't emit any lines, but the actual content of the window is still only in the top 30 lines. However, the terminal app has still moved 20 lines down from the scrollback back into the viewport. So the terminal's cursor is at y=50 now, but conpty's is at 30. This means that the terminal and conpty are out of sync, and there's not a good way of re-syncing these. It's very possible (trivial in `powershell`) that the new output will jump up to y=30 override the existing output in the terminal buffer. The Windows Terminal is already prepared for this quirky behavior, so it doesn't keep the output at the bottom of the window. It shifts it's viewport down to match what conpty things the buffer looks like. What happens when we have passthrough mode and WT is like "I would like quirky resize"? I guess things will just work fine, cause there won't be a buffer behind the passthrough app that the terminal cares about. Sure, in the passthrough case the Terminal could _not_ quirky resize, but the quirky resize won't be wrong.
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Summary of the Pull Request
This is a fix that technically was caused by #357, though we didn't have the Terminal at the time, so I only fixed conhost then. When a client app prints the very last column in the buffer, the cursor is often not actually moved to the next row quite yet. The cursor usually just "floats" on the last character of the row, until something happens. This could be a printable character, which will print it on the next line, or a newline, which will move the cursor to the next line manually, or it could be a backspace, which might take the cursor back a character.
Conhost and gnome-terminal behave slightly differently here, and wt behaves differently all together. Heck, conhost behaves differently depending on what output mode you're in.
The scenario in question is typing a full row of text, then hitting backspace to erase the last char of the row.
What we were emitting before in this case was definitely wrong - we'd emit a space at that last row, but then not increment our internal tracker of where the cursor is, so the cursor in conpty and the terminal would be misaligned. The easy fix for this is to make sure to always update the
_lastTextmember appropriately. This is theRightExclusivechange.The second part of this change is to not be so tricksy immediately following a "delayed eol wrap". When we have just printed the last char like that, always use the VT sequence CUP the next time the cursor moves. Depending on the terminal emulator and it's flags, performing a BS in this state might not bring the cursor to the correct position.
References
#405, #780, #357
PR Checklist
Detailed Description of the Pull Request / Additional comments
With the impending #405 PR I have, this still works, but the sequences that are emitted change, so I didn't write a test for this currently.
Validation Steps Performed
Tried the scenario for both #357 and #1245 in inception,
gnome-temrinalandwtall, and they all display the cursor correctly.