The 'arabicshape' feature of vim is a transformation of unicode text to
make arabic and some related scripts look better at display time. In
particular the content of a cell will be adjusted depending on the
(original) content of the cells just before and after it.
This is implemented by the arabic_shape() function in nvim. Before this
commit, shaping was invoked in four different contexts:
- when rendering buffer text in win_line()
- in line_putchar() for rendering virtual text
- as part of grid_line_puts, used by messages and statuslines and
similar
- as part of draw_cmdline() for drawing the cmdline
This replaces all these with a post-processing step in grid_put_linebuf(),
which has become the entry point for all text rendering after recent
refactors.
An aim of this is to make the handling of multibyte text yet simpler.
One of the main reasons multibyte chars needs to be "parsed" into
codepoint arrays of composing chars is so that these could be inspected
for the purpose of shaping. This can likely be vastly simplified in many
contexts where only the total length (in bytes) and width of composed
char is needed.
This finalizes the long running refactor from the old TUI-focused grid
implementation where text-drawing cursor was not separated from the
visible cursor.
Still, the pattern of setting cursor position together with updating a
line was convenient. Introduce grid_line_cursor_goto() to still allow
this but now being explicit about it.
Only having batched drawing functions makes code involving drawing
a bit longer. But it is better to be explicit, and this highlights
cases where multiple small redraws can be grouped together. This was the
case for most of the changed places (messages, lastline, and :intro)
msg_puts_display was more complex than necessary in nvim, as in
nvim, it no longer talks directly with a terminal.
In particular we don't need to scroll the grid before emiting the last
char. The TUI already takes care of things like that, for terminals
where it matters.
Problem:
Crash from:
set cmdheight=0 redrawdebug=invalid
resize -1
Solution:
Do not invalidate first `p_ch` `msg_grid` rows in `update_screen` when
scrolling the screen down after displaying a message, because they may
be used later for drawing cmdline.
Fixes#22154
Problem: Wrong curswant when clicking on empty line or with vsplits.
Solution: Don't check for ScreenCols[] before the start of the window
and handle empty line properly.
closes: vim/vim#1313203cd697d63
Previously, a screen cell would occupy 28+4=32 bytes per cell
as we always made space for up to MAX_MCO+1 codepoints in a cell.
As an example, even a pretty modest 50*80 screen would consume
50*80*2*32 = 256000, i e a quarter megabyte
With the factor of two due to the TUI side buffer, and even more when
using msg_grid and/or ext_multigrid.
This instead stores a 4-byte union of either:
- a valid UTF-8 sequence up to 4 bytes
- an escape char which is invalid UTF-8 (0xFF) plus a 24-bit index to a
glyph cache
This avoids allocating space for huge composed glyphs _upfront_, while
still keeping rendering such glyphs reasonably fast (1 hash table lookup
+ one plain index lookup). If the same large glyphs are using repeatedly
on the screen, this is still a net reduction of memory/cache
consumption. The only case which really gets worse is if you blast
the screen full with crazy emojis and zalgo text and even this case
only leads to 4 extra bytes per char.
When only <= 4-byte glyphs are used, plus the 4-byte attribute code,
i e 8 bytes in total there is a factor of four reduction of memory use.
Memory which will be quite hot in cache as the screen buffer is scanned
over in win_line() buffer text drawing
A slight complication is that the representation depends on host byte
order. I've tested this manually by compling and running this
in qemu-s390x and it works fine. We might add a qemu based solution
to CI at some point.
The removes the previous restriction that nvim_buf_set_extmark()
could not be used to highlight arbitrary multi-line regions
The problem can be summarized as follows: let's assume an extmark with a
hl_group is placed covering the region (5,0) to (50,0) Now, consider
what happens if nvim needs to redraw a window covering the lines 20-30.
It needs to be able to ask the marktree what extmarks cover this region,
even if they don't begin or end here.
Therefore the marktree needs to be augmented with the information covers
a point, not just what marks begin or end there. To do this, we augment
each node with a field "intersect" which is a set the ids of the
marks which overlap this node, but only if it is not part of the set of
any parent. This ensures the number of nodes that need to be explicitly
marked grows only logarithmically with the total number of explicitly
nodes (and thus the number of of overlapping marks).
Thus we can quickly iterate all marks which overlaps any query position
by looking up what leaf node contains that position. Then we only need
to consider all "start" marks within that leaf node, and the "intersect"
set of that node and all its parents.
Now, and the major source of complexity is that the tree restructuring
operations (to ensure that each node has T-1 <= size <= 2*T-1) also need
to update these sets. If a full inner node is split in two, one of the
new parents might start to completely overlap some ranges and its ids
will need to be moved from its children's sets to its own set.
Similarly, if two undersized nodes gets joined into one, it might no
longer completely overlap some ranges, and now the children which do
needs to have the have the ids in its set instead. And then there are
the pivots! Yes the pivot operations when a child gets moved from one
parent to another.
Problem:
* The guessed botline might be smaller than the actual botline e.g. when
there are folds and the user is typing in insert mode. This may result
in incorrect treesitter highlights for injections.
* botline can be larger than the last line number of the buffer, which
results in errors when placing extmarks.
Solution:
* Take a more conservative approximation. I am not sure if it is
sufficient to guarantee correctness, but it seems to be good enough
for the case mentioned above.
* Clamp it to the last line number.
Co-authored-by: Lewis Russell <me@lewisr.dev>
Problem: Wrong cursor position with virtual text before double-width
char at window edge.
Solution: Check for double-width char before adding virtual text size.
closes: vim/vim#12977ac2d8815ae
Problem: Wrong cursor position with virtual text before a whitespace
character and 'linebreak'.
Solution: Always set "col_adj" to "size - 1" and apply 'linebreak' after
adding the size of 'breakindent' and 'showbreak'.
closes: vim/vim#129566e55e85f92
N/A patches:
vim-patch:9.0.1826: keytrans() doesn't translate recorded key typed in a GUI
