This is strictly speaking not correct, since we're not treating a lot
of characters that should switch state as part of the OSC string.
The correct way would be to have a specific OSC UTF8 state that parses
UTF8 strings.
The grid is now represented with an array of row *pointers*. Each row
contains an array of cells (the row's columns).
The main point of having row pointers is we can now move rows around
almost for free.
This is useful when scrolling with scroll margins for example, where
we previously had to copy the lines in the margins. Now it's just a
matter of swapping two pointers.
* action() returns void - this gets rid of checks in vt_from_slave()
* split up ACTION_PRINT into ACTION_PRINT (ASCII) and ACTION_UTF8_PRINT
ACTION_PRINT is on the hot path, and we want it streamlined.
* Remove run-time checkout for unimplemented state transitions, as we
shouldn't have any of those left.
* Don't re-load current VT state on each iteration in vt_from_slave()
This adds a pointer to the first cell on the current line. This
pointer must be updated every time the row changes.
The advantage is mainly that PRINT doesn't have to call
grid_get_range(), which is fairly expensive.
Vim, for example, changes the scroll region every time you scroll a
single line. Thus, resetting the damage queue is slow.
This reworks the damage handling of scroll updates:
* Split damage queue into two: one for scroll operations and one for
update/erase operations.
* Don't separate update/erase operations inside/outside the scroll
region
* Store the current scroll region in the scroll damage operation. This
allows us to stack multiple scroll operations with different scroll
regions.
* When updating update/erase operations after a scroll operation,
split the update/erase operations if necessary (the current scroll
operation may have a scroll region different from before, thus
forcing us to split existing update/erase operations.
* The renderer no longer erases after a scroll. The scroll operation
also adds an erase operation. This also means that erase operation
are subject to adjustments by later scroll operations.
This is largely untested, but existing scrolling code has been
converted to using a terminal-global scrolling region that is defined
as start-end of the scrollable region.
This is compared to the old code where the scrolling region where
defined in terms of marginals, counted in lines from top and from
bottom.
