set ambiwidth=double will cause display error

[Alaskra]

Neovim version (nvim -v)

NVIM v0.7.0 Build type: Release

Vim (not Nvim) behaves the same?

no, vim8.2

Operating system/version

manjaro

Terminal name/version

terminator

$TERM environment variable

xterm-256color

Installation

AUR

How to reproduce the issue

1. nvim --clean
2. paste this line: 因此如果您在网页版的坚果云发现同一个目录下有两个名称为“Nutstore”和“nutstore”（小写的“n”）的文件/文件夹，在Windows/Mac系统上其中一个文件/文件夹后面会加上“大小写冲突”的字样
3. :set ambiwidth=double
4. mouse drag to change terminal window width, you will see the symbol > which break a line misdisplay.
   

Expected behavior

there won't any character in the right of the symbol >.

Actual behavior

there are some character in the right of the symbol >.

[zeertzjq]

Related: #15898

[zeertzjq]

This small change may "fix" the problem:

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;
   }

But this "fix" just disables a bunch of performance improvements.

[zeertzjq]

A less drastic solution is to only force repositioning cursor after printing an ambiguous width character:

diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index e2289eb9c..2490104b6 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -748,6 +748,9 @@ static void print_cell(UI *ui, UCell *ptr)
   update_attrs(ui, ptr->attr);
   out(ui, ptr->data, strlen(ptr->data));
   grid->col++;
+  if (utf_ambiguous_width(utf_ptr2char(ptr->data))) {
+    grid->row = -1;
+  }
   if (data->immediate_wrap_after_last_column) {
     // Printing at the right margin immediately advances the cursor.
     final_column_wrap(ui);
@@ -1439,6 +1442,9 @@ static void tui_raw_line(UI *ui, Integer g, Integer linerow, Integer startcol, I
     grid->cells[linerow][c].attr = attrs[c - startcol];
   }
   UGRID_FOREACH_CELL(grid, (int)linerow, (int)startcol, (int)endcol, {
+    if (cell->data[0] == NUL && grid->row == -1) {
+      continue;
+    }
     cursor_goto(ui, (int)linerow, curcol);
     print_cell(ui, cell);
   });