Focus problems with tabbing software

[meyergru]

This seems to be a hard problem - I cannot even lay my finger on what caused this:

When I use KiTTY with mRemoteNG, when I start a longer-running program in a tab, then change focus to another application and return after a few seconds, the tab does not get back its focus - what is more, the output of the started program does only become visible after I scroll back and forth. It looks like the KiTTY tab gets somehow "suspended", like XOFF had been given. I think it happens only when the screen is full, i.e. when the scrollbar is active.

While I know that this is not a pure KiTTY problem, as I can see when I try the same outside mRemoteNG, this does not happen with PuTTY and mRemoteNG.

Also, this did not happen until about a few weeks ago. I have even reverted mRemoteNG and KiTTY to older versions, with which to my own observations, this problem was not present. I rolled back KiTTY to 0.74 as well, to no avail.

I wonder if this correlates somehow to https://github.com/cyd01/KiTTY/issues/345 and https://github.com/cyd01/KiTTY/issues/344 or if it has been introduced by a recent Windows 10 update.