Previously, every window resize reinitialised the tab stops to the
default of every 8 columns, discarding any stops set via HTS or cleared
via TBC. ECMA-48 only treats RIS, DECSTR, and DECCOLM as events that
reset tab stops, and other terminal emulators all preserve user-set
stops across an interactive resize.
Copy the surviving prefix of the previous tab stops into the freshly
allocated array on both main and alt screens. Newly added columns when
growing the window keep the default every 8 columns pattern. Also point
the active tabstops pointer at the alt screen's array when a resize
happens while the alt screen is active, instead of unconditionally
resetting it to the main screen's array.
Signed-off-by: Ayman Bagabas <aymanbagabas@gmail.com>
3138ae4aad