This patch takes a bit from the foreground color value in a
cell (todo: split up foreground/background into bitfields with a
separate field for 'foreground/background' has been set), and only
re-renders cells that aren't marked as clean.
Note: we use a 'clean' bit rather than a 'dirty' bit to make it easy
to erase cells - we can (keep doing) do that by simply memsetting a
cell range to 0.
Since newly scrolled in lines will be erased, we want them in the
cache.
So, allocate and prefetch new lines, then repair non-scrolling
regions (to give the prefetch time to actually fetch the
data). Finally, erase the newly scrolled in lines.
This also fixes a bug where the fixup for the non-scrolling regions
could crash on an unallocated row (we were accessing rows that would
be, but hadn't yet been, scrolled in).
The row array may now contain NULL pointers. This means the
corresponding row hasn't yet been allocated and initialized.
On a resize, we explicitly allocate the visible rows.
Uninitialized rows are then allocated the first time they are
referenced.
linefeed moves cursor down one row (columns stays the same), or, if
the cursor is at the last row, scrolls up one row.
reverse_index does the opposite; it moves the cursor *up* one row, or,
if the cursor is at the top row, scrolls *down* one row.
Can scroll up and down, and stops when the beginning/end of history is
reached.
However, it probably breaks when the entire scrollback buffer has been
filled - we need to detect when the view has wrapped around to the
current terminal offset.
The detection of when we've reached the bottom of the history is also
flawed, and only works when we overshoot the bottom with at least a
page.
Resizing the windows while in a view most likely doesn't work.
The view will not detect a wrapped around scrollback buffer. I.e. if
the user has scrolled back, and is stationary at a view, but there is
still output being produced. Then eventually the scrollback buffer
will wrap around. In this case, the correct thing to do is make the
view start following the beginning of the history. Right now it
doesn't, meaning once the scrollback buffer wraps around, you'll start
seeing command output...
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.
This optimizes the normal scrolling case; updates are done at the
bottom of the screen and then scrolled up.
In this case, the damage list will be a more or less sorted list of
updates, oldest first.
If we're scrolling a lot, the oldest updates will eventually scroll
off screen. In this case, there's no need to keep them in the damage
list.
So, when scrolling, loop the damage list and adjust/remove updates
that have scrolled off screen (either partially, or completely).
Stop looping as soon as we see an update that has *not* scrolled off
screen.
Note that this means there may be update items in the damage list
that *has* scrolled off screen. This is especially true for random
screen writes (i.e. typical to some synthetic benchmarks).
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.
Since horizontal cursor movement is clamped to the current line, we
can calculate the new linear cursor without any expensive
multiplications and/or divisions.
