windows: monitorTtySize correctly by polling

[ahmetb]

This change makes monitorTtySize work correctly on windows by polling
into win32 API to get terminal size (because there's no SIGWINCH on
windows) and send it to the engine over Remove API properly.

Average getTtySize takes around 10-40 ms on an average windows machine
as far as I can tell (used go benchmarks), therefore in a for loop, checking
every 250ms if the size has changed since previous measurement or not.
If so, making the rest API call to update the term size.

That should be good enough to emulate SIGWINCH semantics on Windows.

I'm not sure if there's a better way to do it on windows, if so,
somebody please send a link 'cause I could not find.

Also not sure if this should go to 1.6 or not, just a UX improvement.

Demo:

(emphasis on sizes shown in the daemon logs) 😄

Signed-off-by: Ahmet Alp Balkan ahmetalpbalkan@gmail.com

[ahmetb]

@jfrazelle Thanks! ❤️ I'm hoping to hear opinions on design, let's give it a day if we can.

[jessfraz]

then let's not do 1.6 and we can see where we land :D

[ahmetb]

@jfrazelle this is safe enough to land in 1.6 and fixes a great deal of user experience on Windows. I don't see why not.

[ahmetb]

OK I found some more info:

https://msdn.microsoft.com/en-us/library/windows/desktop/ms686033(v=vs.85).aspx
In win32 API if we SetConsoleMode with ENABLE_WINDOW_INPUT bit, “User interactions that change the size of the console screen buffer are reported in the console's input buffer.”

So it is possible to do this without polling.

However, implementing that is probably beyond my ability at this time (I'm not very familiar with console input buffer is processed) and this proposed solution just works, too. Implementing ENABLE_INPUT_WINDOW would also require refactoring to invert the flow (i.e. currently the monitorTtySize is in api/client package and asks term package for events/size. If we refactor it would be platform specific and this method would go to terminal packages i.e. pkg/term & pkg/term/winconsole).

[crosbymichael]

Make sense to me,

LGTM

[ahmetb]

ping: @tiborvass @icecrime

[crosbymichael]

ping @jfrazelle @tiborvass

[jessfraz]

LGTM

[tiborvass]

LGTM

@ahmetalpbalkan I still see the panic unfortunately :( I believe it's as the buffer grows. After doing opening vim a couple of times, I made the window full screen and it panicked. But it's not related to the winresize itself, more of filling in buffers (and there are some dangling pointers in there that would need to be hunted somehow).