Vim in Alacritty and inside tmux cannot display italic text

Question

I am trying to have a better visualization while editing Markdown file in vim, I try to visualize the italic and bold text. However, I found the bold italic text work, while the italic itself doesn't work. It happens outside and insde tmux. I have try use another font, while the italic text itself still not display properly. I don't why the bold italic text can work.

Version of OS, Vim and Terminal emulator:

MacOS : 12.6
Vim : 9.0
Alacritty : 0.11.0

inside alacritty.yml:

font:
  normal:
    family: Menlo 
  size: 14.0

Inside .vimrc:

set background=dark
if !has('gui_running') && &term =~ '^\%(screen\|tmux\)'
  let &t_8f = "\<Esc>[38;2;%lu;%lu;%lum"
  let &t_8b = "\<Esc>[48;2;%lu;%lu;%lum"
endif
syntax on
set termguicolors
colorscheme onedark

Inside .tmux.conf:

set -g default-terminal "tmux-256color"
set -ag terminal-overrides ",xterm-256color:RGB"

The terminal emulator does support italic:

Screenshot of the issue in markdown file:

---

Here is the lines in ~/.vim/colors/onedark.vim that related to markdown italic highlight.

Answer 1

It looks like your italic text shouldn't be blue to begin with, so I would investigate why this is the case.

You should probably start by identifying the actual highlight group used for _Italic text_.

1. Execute this command:

   :command! SS echo map(synstack(line('.'), col('.')), 'synIDattr(v:val, "name")')
   

2. Execute :SS with the cursor on _Italic text_.

   It should echo something like this:

   ['markdownItalic']
   

Report back with the actual output.

Answer 2

I have find a solution. Add highlight group to each items I want it in italic in the color scheme soruce file:

highlight foo cterm=italic

It seems like my color scheme cannot handle with italic text, which require me to add those lines manually. The color scheme I am using are onedark for Vim.