Re: testsuite under wine

[Jacob Bachmeyer <jcb62281@gmail.com>]

Jacek Caban wrote:
> On 12/23/22 04:51, Jacob Bachmeyer wrote:
>> Eric Pouech wrote:
>>> Le 22/12/2022 à 05:16, Jacob Bachmeyer a écrit :
>>>>> I think that it would not be enough. The way Windows consoles work 
>>>>> is that we manage complete internal screen buffer and emit output 
>>>>> that synchronizes the buffer with Unix terminal inside conhost.exe 
>>>>> process. It means that its output heavily processed and may be 
>>>>> very different from what application writes to its console handle. 
>>>>> While escape codes discussed in this thread are the most prominent 
>>>>> difference (and that part could, in theory, be improved on our 
>>>>> side), there are more differences. For example, if application 
>>>>> writes "\rA\rB\rC", conhost will process it, update its internal 
>>>>> buffer which changes just one character and cursor position, and 
>>>>> emit sequence to update it in Unix terminal, which could be just 
>>>>> "\rC" (or even "C" if cursor was already at the beginning of the 
>>>>> line). Another example would be long lines: conhost will emit 
>>>>> additional EOLs instead of depending on embedder to wrap the line.
>>>>
>>>> So conhost is essentially a Wine-specific screen(1) in that sense, 
>>>> except that it translates Windows screen buffer manipulations 
>>>> instead of VT100 escape codes?  As I understand ncurses also 
>>>> implements most of this; perhaps simply delegating output to 
>>>> ncurses would solve the problem?  If output were simply delegated 
>>>> to ncurses, (as I understand) setting TERM=dumb should be effective 
>>>> to eliminate escape codes from the output, since the "dumb" 
>>>> terminal does not support them.
>>>
>>> unfortunately, things are not as simple as that: on one hand we need 
>>> to mimic Windows behavior, and on the other hand let apps running in 
>>> wine behave like regular posix applications <g>
>>>
>>> (Note: conhost(.exe) is not wine specific, it's part of the way 
>>> windows handle the console input/output)
>>
>> Right.  So that is the name of the program that manages consoles in 
>> Windows.  I knew it was not cmd.exe itself.  I was testing an 
>> understanding that conhost.exe in Wine is essentially similar to GNU 
>> screen, in that both emulate a console/terminal using a *nix 
>> terminal.  If so, then it should be possible to delegate the actual 
>> output (including reductions like the example "\rA\rB\rC" to "\rC") 
>> to the ncurses library and get proper sensitivity to TERM "for free" 
>> as well.
>>
>> To do that, conhost.exe would need to translate the Windows console 
>> buffer manipulations into curses operations, or possibly lower-level 
>> terminfo operations, if you still want to roll your own optimization 
>> code.  If this were done, you could check if the current terminal has 
>> sufficient support to properly emulate a Windows console and switch 
>> to "raw" mode if the needed terminfo capabilities are not found.  
>> Setting TERM=dumb in the environment would then force the use of 
>> "raw" mode.
>
>
> Yes, an analogy to screen is right in many aspects, but there are also 
> architectural difference that require implementation to be very 
> different. ncurses operates on tty file descriptors backed by OS 
> kernel. conhost needs to be able to operate on Windows names pipes, 
> which are not associated with any file descriptor in Wine.

Please explain this.  Programs using curses make calls into the curses 
library, which ultimately produces I/O on a tty file descriptor.  It 
seems to me that conhost is in the same position as the curses library:  
programs use Windows API calls for the console which [...across an IPC 
bridge of some type?...] result in dispatches in conhost that ultimately 
produce I/O on a tty file descriptor.  Does conhost not actually hold 
the file descriptor, instead performing translations and sending the 
result back to the client process, which writes it out?

If full curses is not usable for architectural reasons, terminfo would 
still be an improvement.  Its setupterm() call may send any known init 
strings, but it could be given either the write end of a pipe or a file 
descriptor open on /dev/null if that is a problem.  The terminfo 
database access functions tparm(), tigetflag(), tigetnum(), and 
tigetstr() all return values to their callers for further processing and 
the information needed to perform curses-style terminal initialization 
is stored as string capabilities in the terminfo database.

> Also my point was that if you capture the output sent by the 
> application to the terminal and match that to a pattern, then any 
> processing made by conhost could cause problems. Please correct me if 
> I'm wrong, but my understanding is that, in the above hypothetical 
> example, a test case doing printf(stdout, "\rA\rB\rC") and matching 
> output to "\rA\rB\rC" would be considered valid (and fail on Wine).

This type of thing is a general problem with testing curses programs, so 
the only difference would be effectively adding curses to programs that 
are not expected to use it.  Yes, this could break testsuites that 
should work, so some kind of full bypass would be very helpful; you 
already have this if wine is run inside a pipeline.

> That's why we're trying to figure out a solution that bypasses conhost 
> and makes the application write directly to stdout, like usual native 
> application would do. Such mode would be less compatible with Windows, 
> but if tests only does simple I/O and no other console interactions, 
> it should work fine. Interpreting TERM=dumb would be a possible 
> solution to enter that mode.

I see two aspects to this, and I think both of them have value as 
improvements to Wine:

1.  Programs that only use the standard handles (a la ISO C) probably do 
not /want/ full compatibility with Windows, so their I/O should be 
direct to the underlying POSIX fds.  Note that line endings are still an 
issue here, but are /not/ Wine's problem---the program's I/O library 
module is generating Windows-style line endings because it was written 
for Windows.

2.  Programs using Windows CUI probably should be mapped to curses; as I 
see it, conhost currently is implementing a subset of curses, poorly 
since it does not use terminfo.  Wine should use curses if $TERM 
supports curses and either pop up an X11 Wine console window or bail out 
if a CUI call is made and $TERM does not support curses.  (Actually, an 
option to explicitly select an X11 Wine console window might be helpful 
for people that want to invoke a Windows CUI program from a graphical 
menu; otherwise, you might end up with the CUI silently appearing on the 
console from which the X session was started... I know adding xterm to 
the mix solves this, but it is a use case.)

I think the best goal here is that, for the standard handles, Wine I/O 
should be equivalent to a network connection (telnet?) to a Windows 
box.  For CUI, Wine should actually use curses or at least terminfo, to 
allow the escape codes produced to match the user's terminal.  The 
user's terminal might not always be a VT100-alike and custom simulated 
terminals could be very reasonable for testing curses TUI programs.  (To 
my knowledge, there are as yet no testsuites that actually /do/ that, 
but the composition seems reasonable to me.)

Finding that NightStrike's MinGW test cases are transparently using CUI 
would be a MinGW issue, not a Wine issue.

It has been a long time since I have looked at Windows API, but I am 
guessing that there is both some equivalent to "fwrite(stdout, ...)" 
(ok, so likely something like 
"WriteToHandle(GetStandardHandle(STANDARD_HANDLE_OUTPUT),...)" if I 
remember the Windows API "style" and its affinity for RSI-supporting 
names correctly) and a more complex API for CUI that is more closely 
akin to curses.  Could you delay initializing conhost until the program 
actually attempts to use CUI features?  For this option, CUIInit() ends 
up calling newterm() and using curses if that succeeds, (possibly, after 
considerable future implementation effort) popping up a Wine console 
window using X11 if $DISPLAY is usable, or bailing out if neither way to 
get a full Windows console works.  Until CUIInit() is called, the 
standard handles are just that and simply mapped through to the 
underlying POSIX handles.

Is this architecturally feasible for Wine to do?


-- Jacob