vim-patch:8.2.{1535,1537,3545}: setcellwidths()

[zeertzjq]

vim-patch:8.2.1535: it is not possible to specify cell widths of characters

Problem: It is not possible to specify cell widths of characters.
Solution: Add setcellwidths().
vim/vim@08aac3c

Co-Authored-By: delphinus me@delphinus.dev

vim-patch:8.2.1537: memory acccess error when using setcellwidths()

Problem: Memory acccess error when using setcellwidths().
Solution: Use array and pointers correctly.
vim/vim@b06a6d5

vim-patch:8.2.3545: setcellwidths() may make 'listchars' or 'fillchars' invalid

Problem: setcellwidths() may make 'listchars' or 'fillchars' invalid.
Solution: Check the value and give an error. (closes vim/vim#9024)
vim/vim@94358a1

Cherry-pick f_setcellwidths() change from patch 9.0.0036.
Cherry-pick 'ambiwidth' docs update from runtime update 079ba76ae7a7.

[delphinus]

Thx for rebasing. Now Neovim's view is broken which Vim can draw validly. I confirmed this on this PR & my one (#13883).

# ℃ <- 0x2103
$ cat /tmp/aaa.txt
'℃'

on Neovim

$ nvim -N -u NONE -i NONE --noplugin +'call setcellwidths([[0x2103, 0x2103, 2]])' /tmp/aaa.txt

$ vim +'call setcellwidths([[0x2103, 0x2103, 2]])' /tmp/aaa.txt

On Neovim, it puts ' over the character ℃.Vim draws separatedly without fail.

[zeertzjq]

I think this is likely because Nvim's TUI is line-based, while Vim's TUI is char-based. Does iTerm2 also behave like this if you cat /tmp/aaa.txt?

[delphinus]

Yes. iTerm2 behaves similarly as U+2301 has 1 width because this option below is disabled in my box.

• Preferences → Profiles → Text → Ambiguous characters are double-width (default: OFF)

OFF	ON

I expect setcellwidths() should work as overwriting this...

I think this is likely because Nvim's TUI is line-based, while Vim's TUI is char-based.

We should adjust logic for win_line() in screen.c ?

[zeertzjq]

win_line() does not need change. It is likely that cursor_goto() and print_cell() in tui/tui.c may need change. Sorry, my previous comment does not make sense.

[zeertzjq]

If performance is not taken into consideration, you may fix this problem by making this small change:

diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index e2289eb9c..78281470d 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -788,6 +788,7 @@ static void cursor_goto(UI *ui, int row, int col)
 {
   TUIData *data = ui->data;
   UGrid *grid = &data->grid;
+  goto safe_move;
   if (row == grid->row && col == grid->col) {
     return;
   }

This change is not desirable as it disables a bunch of performance improvements.

[zeertzjq]

I have a solution to the problem mentioned above in #19686.