Characters disappear when NERDTree pane opens

[cyril-s]

Describe the bug
Some characters disappear when toggling NERDTree pane open, notably lines where NERDTree displays directories are affected.

Technical information:

• OS: Debian sid
• Neovim version: NVIM v0.4.4
• Neovim-Gtk build version: 925382a
• Build dependencies

||/ Name                       Version       Architecture Description
+++-==========================-=============-============-===================================================
ii  libatk1.0-dev:amd64        2.36.0-2      amd64        Development files for the ATK accessibility toolkit
ii  libcairo2-dev:amd64        1.16.0-4      amd64        Development files for the Cairo 2D graphics library
ii  libgdk-pixbuf2.0-dev:amd64 2.40.0+dfsg-5 amd64        GDK Pixbuf library (development files)
ii  libglib2.0-dev:amd64       2.64.4-1      amd64        Development files for the GLib library
ii  libgtk-3-dev:amd64         3.24.22-1     amd64        development files for the GTK library
ii  libpango1.0-dev:amd64      1.46.1-1      amd64        Development files for the Pango

• Rustc version: rustc 1.46.0 (04488afe3 2020-08-24)

Reverting libpango to 1.44 fixes the issue

[jacobmischka]

I'm willing to bet #254 is related to this as well. I haven't dug into it yet, but I hope to soon (maybe not until hacktoberfest, though).

[pitbuster]

Hi @jacobmischka, have you had any chance to look into this?

I can help if needed (by running test, debugging, etc).

[jacobmischka]

I haven't, sorry.

[theHamsta]

I only had a short browse around the code base. What makes me a bit suspicious is this double_width. Could it be that neovim-gtk does not support triple-width, 4-byte characters? But it's only a guess since I didn't review it in detail It's just for ligatures

#[derive(Clone)]
pub struct Cell {
    pub hl: Rc<Highlight>,
    pub ch: String,
    pub dirty: bool,
    pub double_width: bool,
}

impl Cell {
    pub fn new_empty() -> Cell {
        Cell {
            hl: Rc::new(Highlight::new()),
            ch: String::new(),
            dirty: true,
            double_width: false,
        }
    }

    pub fn clear(&mut self, hl: Rc<Highlight>) {
        self.ch.clear();
        self.hl = hl;
        self.dirty = true;
        self.double_width = false;
    }
}

one usage

        for (cell_idx, cell) in line.line.iter().enumerate() {
            if cell.double_width {
                continue;
            }

            if !cell.ch.is_empty() {
                line_str.push_str(&cell.ch);
            } else {
                line_str.push(' ');
            }
            let len = line_str.len() - byte_offset;

            for _ in 0..len {
                cell_to_byte.push(cell_idx);
            }

            let next = style_attr.next(byte_offset, byte_offset + len, cell, hl);
            if let Some(next) = next {
                style_attr.insert_into(&attr_list);
                style_attr = next;
            }

            byte_offset += len;
        }

Could also be that those are double_with ligatures to be drawn. neovim-gtk has at least two character ligatures as -> . Should take a more detailed look.

  let len = line_str.len() - byte_offset;

But I suppose it has to be a byte != str.len issue.

[cyril-s]

After system upgrade the issue is fixed for me

cairo 1.17.4-3
glib2 2.66.4-2
gtk3 1:3.24.24-2
pango 1:1.48.1-1