fix(windows): restore console modes before exit

[insomnimus]

On Windows, the console modes are altered by wget2 (via SetupConsoleHandlein libwget), to enable virtual terminal sequences. However it's not restored before exit; this causes problems such as key binds not working properly, even after the wget2 process exits (#311).

This PR addresses the problem by saving the console modes at the start of main, and then restoring them before main returns.

I'm not well versed in C let alone this code base, so the PR might not be up to the project's standards. Do let me know if I should change anything.

Fixes: #311

[gvanem]

What if a CTRL_C_EVENT or CTRL_BREAK_EVENT gets raised? AFAICS, there's no call to SetConsoleCtrlHandler() to trap and restore the terminal-state.

[insomnimus]

Actually cancelling a download in that fashion still seems to trigger the code that restores console modes, maybe it's not necessary to call SetConsoleCtrlHandler?

I cannot determine why this works when ctrl-c/break gets issued. It still ends up restoring console modes.

[gvanem]

It still ends up restoring console modes.

Are you sure? Neither SetConsoleCtrlHandler() nor SetConsoleMode() are called in Wget2. And there's a difference in how conhost.exe handles Ctrl-C vs. Ctrl-Break: https://learn.microsoft.com/en-us/windows/console/ctrl-c-and-ctrl-break-signals

[insomnimus]

Ah, you're right: ctrl-break still leaves the console modified; however ctrl-c does not.

So the solution is SetConsoleCtrlHandler, however since it takes a handler function, how should I go about not duplicating the cleanup code at the end of main? Also it looks like the previous console modes have to become globals now, which I'm not a fan of.

As a side note I'm still not sure why the patch works for ctrl-c.

[insomnimus]

Also SetConsoleMode is actually called indirectly:

• init in src/options.c
• calls log_init in src/log.c
• calls wget_console_init in libwget/console.c
• calls SetupConsoleHandle also in libwget/console.c
• which finally calls SetConsoleMode

That's how i diagnosed the issue at first: commenting out SetConsoleMode calls inside SetupConsoleHandle, which worked but is of course undesirable.

[insomnimus]

Are there any suggestions on how to proceed?

[rockdaboot]

I think you should add your code to the global constructor and the global destructor.

The destructor should be called at program exit. Please test it and give a feedback.

[insomnimus]

Sorry for the delay; I got hit with the seasonal flu.

I've moved the cleanup to libwget/init.c as you suggested:

• The initial console modes are obtained and stored in INITIALIZER().
• A handler is registered via SetConsoleCtrlHandler(), also in INITIALIZER().
• The handler simply calls exit(2) if the signal is ctrl+c or ctrl+break; it ignores other signals, letting any other handler, if any, handle them. This triggers whatever's registered with atexit(), including our destructor global_exit().
• The console modes are restored in global_exit().

Let me know if I should change anything.

[insomnimus]

Oh also I've tested this and it works for both ctrl+c and ctrl+break.

[rockdaboot]

Thanks for your contribution, manually pushed (changed the commit message).