Turning off the cursor requires visible output?

[vefatica]

If I do this,

	printf("\x1b[?25l"); // cursor off
	Sleep(5000);
	printf("x");
	Sleep(5000);

the cursor is on during the first Sleep and off during the second Sleep. What's up with that? Is there any kludge that will turn off the cursor immediately without producing any visible output?

[vefatica]

That was in WT. In a console, the cursor is off for the whole 10 seconds.

[j4james]

Yeah, this is a bug - the cursor should turn off immediately. I think it's another regression from PR #17194. The VtEngine doesn't see the cursor visibility change as something it needs to handle, so it skips painting that frame.

This is a bit messy to fix because the VtEngine doesn't have access to that state. But if we added a cursorVisible parameter to the StartPaint method, and then made the renderer pass in the _currentCursorOptions.isVisible flag, we could compare that against the _lastCursorIsVisible field to detect whether the visibility has changed. If it has, we shouldn't abort the paint.

I think the check would need to be added to the XtermEngine::StartPaint method where it's testing hr != S_OK.

terminal/src/renderer/vt/XtermEngine.cpp

Lines 40 to 41 in 295cd17

	const auto hr = VtEngine::StartPaint();
	if (hr != S_OK)

That test would need to be extended to something like this:

if (hr != S_OK && (int)cursorVisible == (int)_lastCursorIsVisible)

However, if we're going to be merging PR #17510 soon, there may not be a need for this fix, unless it's something we want to backport to version 1.21.

[vefatica]

OK, thanks for the info @j4james . Is that merge likely to happen in the next preview? I try to use the latest preview though I don't check for a new one as often as I used to. I just want the cursor off in transient/pipe instances. I have a couple ways to do that (plugin DLL, startup script) and the results have never been good. As you probably know, SetConsoleCursorInfo with bVisible=FALSE is no better.

What about a kludge? Apparently writing something to the screen gets someone's attention. Hmmm! I wonder about writing an nbsp (0xA0) followed by a cursor_left_one_column ... something to try.

[j4james]

I don't have any insider knowledge regarding the release schedule, but I think there's a good chance it'll be included in the next preview. There's actually already a version of that PR in the nightly canary build if you want to try that out.

[lhecker]

We're currently planning to release the next Preview version (one that includes #17510) at the end of August.