Ability to use different highlight groups for labels depending on its content (character)

[Andrew15-5]

I've noticed that I have a hard time quickly distinguishing some of the lower and upper case letters with just a primary highlight group. Is it possible to make it more customizable and, for example, make all uppercase letters red, and the rest of characters — green?

[ggandor]

It just occurred to me that we can do things like that with on_beacons:

-- `on_beacons` is an unofficial hook, called every time Leap updates
-- the screen. See #65 and `beacons.fnl`.
require('leap').opts.on_beacons = function (targets, _, _)
  for _, target in ipairs(targets) do
    -- In this example, if the label character is uppercase, we set the
    -- highlight group to our custom one.
    if target.label and target.beacon then
      -- target.beacon looks like: { <offset>, <extmark_opts> }
      -- extmark_opts looks like: { virt_text = {{ <char>, <hl-group> }} }
      --   see `:help nvim_buf_set_extmark()`
      local vtext = target.beacon[2].virt_text[1]
      local char, hl_group = unpack(vtext)
      if hl_group == 'LeapLabel' then
        local condition = (char == char:upper())  -- <<< put your custom conditional logic here
        if condition then
          vtext[2] = 'LeapLabelSpecial'  -- <<< and your desired tweaks here
        end
      end
    end
  end
  -- We do not want to completely override the original logic; returning
  -- true tells Leap to continue with the native function body (i.e., do
  -- everything else as usual, with the above tweaks).
  return true
end

-- If you want to define the custom highlight group based on the current values
-- of LeapLabel, instead of doing it from scratch for every color scheme:
vim.api.nvim_create_autocmd('ColorScheme', {
  group = vim.api.nvim_create_augroup('LeapCustomHighlight', {}),
  callback = function ()
    local leap_label_special = vim.deepcopy(vim.api.nvim_get_hl(0, {
      name = 'LeapLabel', link = false
    }))
    leap_label_special.bold = true  -- <<< do modifications to the group here
    vim.api.nvim_set_hl(0, 'LeapLabelSpecial', leap_label_special)
  end
})

[Andrew15-5]

Which version of plugin and Neovim it supposed to work with? I'm on 346a16e and 0.10.4.

E5108: Error executing lua: /home/user/.config/nvim/lua/custom/configs/leap.lua:149: attempt to index field 'virt_text' (a nil value)
stack traceback:
        /home/user/.config/nvim/lua/custom/configs/leap.lua:149: in function 'on_beacons'
        ...ew/.local/share/nvim/lazy/leap.nvim/lua/leap/beacons.lua:172: in function 'f'
        ...ndrew/.local/share/nvim/lazy/leap.nvim/lua/leap/main.lua:312: in function 'with_highlight_chores'
        ...ndrew/.local/share/nvim/lazy/leap.nvim/lua/leap/main.lua:416: in function 'get_second_pattern_input'
        ...ndrew/.local/share/nvim/lazy/leap.nvim/lua/leap/main.lua:702: in function 'leap'
        .../user/.local/share/nvim/lazy/leap.nvim/plugin/init.lua:60: in function <.../user/.local/share/nvim/lazy/leap.nvim/plugin/init.lua:60>

[ggandor]

Update Leap (6bec01e changed the structure of target.beacon), stable Neovim is fine.

[Andrew15-5]

Thanks, it works. I'm not a heavy Neovim coder, so idk why the colorscheme automatic command didn't work.

  vim.api.nvim_create_autocmd("ColorScheme", {
    group = vim.api.nvim_create_augroup("LeapCustomHighlight", {}),
    callback = function()
      local leap_label_special = vim.deepcopy(vim.api.nvim_get_hl(0, {
        name = "LeapLabel",
        link = false,
      }))
      -- leap_label_special.bold = true -- <<< do modifications to the group here
      -- leap_label_special.bg = "LeapLabel"
      -- leap_label_special.bg = "#ccff88"
      -- leap_label_special.bg = 1
      -- vim.api.nvim_set_hl(0, "LeapLabelSpecial", leap_label_special)
      -- vim.api.nvim_set_hl(0, "LeapLabelSpecial", { fg = "Black", bg = "#fcaf88", bold = true })
    end,
  })

But putting this outside just works:

vim.api.nvim_set_hl(0, "LeapLabel", { fg = "Black", bg = "#ccff88", bold = true })
vim.api.nvim_set_hl(0, "LeapLabelSpecial", { fg = "Black", bg = "#fcaf88", bold = true })

So I think for now I'll use this:

-- https://github.com/ggandor/leap.nvim/issues/259#issuecomment-2952599204
local function upper_lower_highlight_groups()
  ---@diagnostic disable-next-line: deprecated
  local unpack = table.unpack or unpack
  -- `on_beacons` is an unofficial hook, called every time Leap updates
  -- the screen. See #65 and `beacons.fnl`.
  require("leap").opts.on_beacons = function(targets, _, _)
    for _, target in ipairs(targets) do
      -- In this example, if the label character is uppercase (non-lowercase),
      -- we set the highlight group to our custom one.
      if target.label and target.beacon then
        -- target.beacon looks like: { <offset>, <extmark_opts> }
        -- extmark_opts looks like: { virt_text = {{ <char>, <hl-group> }} }
        --   see `:help nvim_buf_set_extmark()`
        local vtext = target.beacon[2].virt_text[1]
        local char, hl_group = unpack(vtext)
        if hl_group == "LeapLabel" then
          local condition = (char ~= char:lower()) -- upper() selects "/" too
          if condition then
            vtext[2] = "LeapLabelSpecial"
          end
        end
      end
    end
    -- We do not want to completely override the original logic; returning
    -- true tells Leap to continue with the native function body (i.e., do
    -- everything else as usual, with the above tweaks).
    return true
  end
end

upper_lower_highlight_groups()

vim.api.nvim_set_hl(0, "LeapLabel", { fg = "Black", bg = "#ccff88", bold = true })
vim.api.nvim_set_hl(0, "LeapLabelSpecial", { fg = "Black", bg = "#fcaf88", bold = true })

I think just from a few tries, it feels very helpful, but only real test drive can say for sure.

Will it eventually be shipped as some neat callback setting? Or added to docs.

[ggandor]

idk why the colorscheme automatic command didn't work

It should work, but you only see the result if you actually change (or reload) the color scheme. (Or restart Neovim.)

[Andrew15-5]

Nothing will happen if I don't restart the editor.

[ggandor]

Will it eventually be shipped as some neat callback setting? Or added to docs.

Now it struck me that we can easily set rainbow-colored labels for treesitter selection too, that would be worth documenting somewhere.