Many include statements use forward slashes, while others use backwards
slashes. This is inconsistent formatting. For this reason, I changed the
backward slashes to forward slashes since that is the standard.
We were using std::basic_string_view as a stand-in for std::span so that
we could change over all at once when C++20 dropped with full span
support. That day's not here yet, but as of 54a7fce3e we're using GSL 3,
whose span is C++20-compliant.
This commit replaces every instance of basic_string_view that was not
referring to an actual string with a span of the appropriate type.
I moved the `const` qualifier into span's `T` because while
`basic_string_view.at()` returns `const T&`, `span.at()` returns `T&`
(without the const). I wanted to maintain the invariant that members of
the span were immutable.
* Mechanical Changes
* `sv.at(x)` -> `gsl::at(sp, x)`
* `sv.c{begin,end}` -> `sp.{begin,end}` (span's iterators are const)
I had to replace a `std::basic_string<>` with a `std::vector<>` in
ConImeInfo, and I chose to replace a manual array walk in
ScreenInfoUiaProviderBase with a ranged-for. Please review those
specifically.
This will almost certainly cause a code size regression in Windows
because I'm blowing out all the PGO counts. Whoops.
Related: #3956, #975.
There is going to be a very long tail of applications that will
explicitly request VT SGR 40/37 when what they really want is to
SetConsoleTextAttribute() with a black background/white foreground.
Instead of making those applications look bad (and therefore making us
look bad, because we're releasing this as an update to something that
"looks good" already), we're introducing this compatibility quirk.
Before the color reckoning in #6698 + #6506, *every* color was subject
to being spontaneously and erroneously turned into the default color.
Now, only the 16-color palette value that matches the active console
background/foreground color will be destroyed, and only when received
from specific applications.
Removal will be tracked by #6807.
Michael and I discussed what layer this quirk really belonged in. I
originally believed it would be sufficient to detect a background color
that matched the legacy default background, but @j4james provided an
example of where that wouldn't work out (powershell setting the
foreground color to white/gray). In addition, it was too heavyhanded: it
re-broke black backgrounds for every application.
Michael thought that it should live in the server, as a small VT parser
that righted the wrongs coming directly out of the application. On
further investigation, however, I realized that we'd need to push more
information up into the server (so that it could make the decision about
which VT was wrong and which was right) than should be strictly
necessary.
The host knows which colors are right and wrong, and it gets final say
in what ends up in the buffer.
Because of that, I chose to push the quirk state down through
WriteConsole to DoWriteConsole and toggle state on the
SCREEN_INFORMATION that indicates whether the colors coming out of the
application are to be distrusted. This quirk _only applies to pwsh.exe
and powershell.exe._
NOTE: This doesn't work for PowerShell the .NET Global tool, because it
is run as an assembly through dotnet.exe. I have no opinion on how to
fix this, or whether it is worth fixing.
VALIDATION
----------
I configured my terminals to have an incredibly garish color scheme to
show exactly what's going to happen as a result of this. The _default
terminal background_ is purple or red, and the foreground green. I've
printed out a heap of test colors to see how black interacts with them.
Pull request #6810 contains the images generated from this test.
The only color lines that change are the ones where black as a
background or white as a foreground is selected out of the 16-color
palette explicitly. Reverse video still works fine (because black is in
the foreground!), and it's even possible to represent "black on default"
and reverse it into "default on black", despite the black in question
having been `40`.
Fixes#6767.
## Summary of the Pull Request
This PR implements a pair of shims for `cmd` and `powershell`, so that their `cls` and `Clear-Host` functions will clear the entire terminal buffer (like they do in conhost), instead of just the viewport. With the conpty viewport and buffer being the same size, there's effectively no way to know if an application is calling these API's in this way with the intention of clearing the buffer or the viewport. We absolutely have to guess.
Each of these shims checks to see if the way that the API is being called exactly matches the way `cmd` or `powershell` would call these APIs. If it does, we manually write a `^[[3J` to the connected terminal, to get he Terminal to clear it's own scrollback.
~~_⚠️ If another application were trying to clear the **viewport** with an exactly similar API call, this would also cause the terminal scrollback to get cleared ⚠️_~~
* [x] Should these shims be restricted to when the process that's calling them is actually `cmd.exe` or `powershell.exe`? Can I even do this? I think we've done such a good job of isolating the client process information from the rest of the host code that I can't figure out how to do this.
- YES, this can be done, and I did it.
* [ ] **TODO**: _While I'm here_, should I have `DoSrvPrivateEraseAll` (the implementation for `^[[2J`, in `getset.cpp`) also manually trigger a EraseAll in the terminal in conpty mode?
## PR Checklist
* [x] Closes#3126
* [x] Actually closes#1305 too, which is really the same thing, but probably deserves a callout
* [x] I work here
* [x] Tests added/passed
* [n/a] Requires documentation to be updated
## Validation Steps Performed
* ran tests
* checked `cls` in the Terminal
* checked `Clear-Host` in the Terminal
* Checked running `powershell clear-host` from `cmd.exe`
