[Bug] Can't get character level highlighting working

[xstoicunicornx]

Description

Firstly, thank you for this fork! Love having the diff1_inline view.

Secondly, this is very low priority issue.

I've been trying to get the character level highlighting mentioned in TIPS.md working in unified diff1_inline view but haven't been successful. Is seems like it doesn't work with tokyonight theme? Are there specific highlights I need to set to get it working?

It is working in diff2 views. Is it possible to apply the same background highlights to the diff1_inline unified view? Even when diff1_inline unified view is working it only does foreground highlights, it would be nice to be able to do background instead.

Expected behavior

character level diff highlighting works

Actual behavior

character level diff highlighting does not work, only line level is working.

Steps to reproduce

1. nvim --clean -u mini.lua
2. :DiffviewOpen (or :DiffviewFileHistory)

Health check

Output of :checkhealth diffview

diffview:                                                                 3 ⚠️

Checking plugin dependencies ~
- ✅ OK nvim-web-devicons installed.
- ⚠️ WARNING Optional dependency 'mini.icons' not found.

Checking VCS tools ~
- The plugin requires at least one of the supported VCS tools to be valid.
- ✅ OK Jujutsu found.
- ✅ OK Jujutsu is up-to-date. (0.40.0)
- ✅ OK Git found.
- ✅ OK Git is up-to-date. (2.39.5)
- ⚠️ WARNING Configured `hg_cmd` is not executable: 'hg'
- ⚠️ WARNING Configured `p4_cmd` is not executable: 'p4'

Log info

Relevant info from :DiffviewLog

############################
### PUT LOG CONTENT HERE ###
############################

Neovim version

NVIM v0.11.5
Build type: Release
LuaJIT 2.1.1765007043
Run "nvim -V1 -v" for more info

Operating system and version

macOS 15.7.7 24G720 arm64

Minimal config

local root = vim.fn.stdpath("run") .. "/nvim/diffview.nvim"
local plugin_dir = root .. "/plugins"
vim.fn.mkdir(plugin_dir, "p")

for _, name in ipairs({ "config", "data", "state", "cache" }) do
	vim.env[("XDG_%s_HOME"):format(name:upper())] = root .. "/" .. name
end

local plugins = {
	{ "nvim-web-devicons", url = "https://github.com/nvim-tree/nvim-web-devicons.git" },
	{ "diffview.nvim",     url = "https://github.com/dlyongemallo/diffview.nvim.git" },
	-- ##################################################################
	-- ### ADD PLUGINS THAT ARE _NECESSARY_ FOR REPRODUCING THE ISSUE ###
	-- ##################################################################
	{ "diffchar.vim",      url = "https://github.com/rickhowe/diffchar.vim.git" },
	{ "tokyonight.nvim",   url = "https://github.com/folke/tokyonight.nvim.git" }
}

for _, spec in ipairs(plugins) do
	local install_path = plugin_dir .. "/" .. spec[1]
	if vim.fn.isdirectory(install_path) ~= 1 then
		if spec.url then
			print(string.format("Installing '%s'...", spec[1]))
			vim.fn.system({ "git", "clone", "--depth=1", spec.url, install_path })
		end
	end
	vim.opt.runtimepath:append(spec.path or install_path)
end

require("diffview").setup({
	-- ##############################################################################
	-- ### ADD DIFFVIEW.NVIM CONFIG THAT IS _NECESSARY_ FOR REPRODUCING THE ISSUE ###
	-- ##############################################################################
	enhanced_diff_hl = true,
	view = {
		default = { layout = "diff1_inline" },
		inline = {
			deletion_highlight = "full_width",
			style = "unified",
		},
		file_history_view = { layout = "diff1_inline" },
		cycle_layouts = {
			default = { "diff1_inline", "diff2_horizontal", },
		},
	}

})

vim.opt.termguicolors = true
vim.cmd("colorscheme tokyonight")

-- ############################################################################
-- ### ADD INIT.LUA SETTINGS THAT ARE _NECESSARY_ FOR REPRODUCING THE ISSUE ###
-- ############################################################################

print("Ready!")

[dlyongemallo]

@xstoicunicornx The way the diff1_inline layout is implemented does not actually use vim's internal diff mode (for technical reasons), so diffchar.vim won't work on it. I've modified the TIPS.md to explain this, and also how to adjust the highlights in that case.

[xstoicunicornx]

Thanks @dlyongemallo ! That is helpful info but I don't think it explains why habamax color scheme has word level highlights in diff1_inline and tokyonight color scheme does not.

For example when I take the mini.lua above and change the theme back to habamax I see added word highlights on the modified lines.

[dlyongemallo]

Is #209 better? The difficulty is in setting sensible defaults which work for most colour schemes while allowing for flexible user overrides. tokyonight is popular enough that I want to support it "out of the box".

[xstoicunicornx]

When I add something like vim.api.nvim_set_hl(0, 'DiffviewDiffTextInline', { bg = '#ffffff' }) while loading your fork as the Diffview dependency I still don't see any change. Do you have a mini.lua you could share to show me how to use properly?

Tbh I still am not sure this is addressing root cause, as I don't think it is a matter of highlights blending into the background.

Using the mini.lua I provided above except with the habamax colorscheme:

This is the same lines except with the 'tokyonight' colorscheme (the diffChange background is very slightly changed but it is there):

I really appreciate you taking the time to get this working but I hesitate to advocate for such a large change when I can't get it to work on my end.

[dlyongemallo]

Did you change your minimal config to test against #209 (currently at commit 77d0341)? You need to set the branch name to diff1_inline_char_hl and then do something like this in your mini.lua:

              if spec.url then
                      print(string.format("Installing '%s'...", spec[1]))
                      local cmd = { "git", "clone", "--depth=1" }
                      if spec.branch then
                              vim.list_extend(cmd, { "--branch", spec.branch })
                      end
                      vim.list_extend(cmd, { spec.url, install_path })
                      vim.fn.system(cmd)
              end

You might have to delete diffview.nvim from the plugins directory first.

If you want to override the colour (though I think you shouldn't have to, with the above change):

require("diffview").setup({ ... })

vim.api.nvim_create_autocmd("ColorScheme", {
  callback = function()
    vim.api.nvim_set_hl(0, "DiffviewDiffTextInline", { bg = "#ffffff" })  -- for example
  end,
})

vim.opt.termguicolors = true
vim.cmd("colorscheme tokyonight")

Let me know if that works or not.

[xstoicunicornx]

Ok! I got it somewhat working but not entirely...

This works:

vim.api.nvim_set_hl(0, "DiffviewDiffTextInline", { fg = "#ffffff" })

None of these work:

vim.api.nvim_set_hl(0, "DiffviewDiffTextInline", { bg = "#ffffff" })
vim.api.nvim_set_hl(0, "DiffText", { fg = "#ffffff" })
vim.api.nvim_set_hl(0, "DiffText", { bg = "#ffffff" })

From the DiffviewDiffTextInline documentation it sounded like maybe fg won't work which is fair but from what it written it seems like bg should work? Also that it should pick up from DiffText?

[dlyongemallo]

Ah, my fix didn't work because of neovim/neovim#31151. I need to look into this some more.

[dlyongemallo]

@xstoicunicornx Can you try again at commit 4ea3fdd? I had to work around some neovim quirks.

[xstoicunicornx]

Success :)

So these all work as expected:

• tokyonight has character level diff highlighting for unified diff1_inline view out of the box
• tokyonight has character level diff highlighting for overleaf diff1_inline view out of the box
• setting DiffviewDiffTextInline highlights

However there were still some things that didn't work how I would have expected according to the documentation:

• when I override DiffText highlights those changes aren't picked up by the unified diff1_inline view (maybe just a limitation that needs to be documented? maybe just leave out of documentation specification as providing the DiffviewDiffTextInline highlight seems sufficient?)
• I couldn't get DiffviewDiffAddInline and DiffviewDiffDeleteInline highlights to work for overleaf diff1_inline view

For my own purposes I am not really interested in the overleaf style, but would hate to introduce bugs just to get my own thing fixed.

[dlyongemallo]

Merged as #209.

[xstoicunicornx]

Thank you @dlyongemallo !!