Programmatic Tab Color based on CWD; And other Tab Title Customization

[KyleKing]

When moving between tabs, I wanted to more clearly see when I change project directories. I've cobbled together a few scripts I've found online to customize the tab. Along with setting the color, the tab will have the process name or icon (e.g. [python3.8] or a font awesome icon for vim, lazygit, etc.). See a quick demo:

Screen.Recording.2024-02-03.at.04.36.25.mov

(Note: you may need to refresh the page to view the video)

local wezterm = require("wezterm")

-- Custom title and icon based on: https://github.com/protiumx/.dotfiles/blob/854d4b159a0a0512dc24cbc840af467ac84085f8/stow/wezterm/.config/wezterm/wezterm.lua#L291-L319
local process_icons = {
    ["bash"] = wezterm.nerdfonts.cod_terminal_bash,
    ["btm"] = wezterm.nerdfonts.mdi_chart_donut_variant,
    ["cargo"] = wezterm.nerdfonts.dev_rust,
    ["curl"] = wezterm.nerdfonts.mdi_flattr,
    ["docker"] = wezterm.nerdfonts.linux_docker,
    ["docker-compose"] = wezterm.nerdfonts.linux_docker,
    ["gh"] = wezterm.nerdfonts.dev_github_badge,
    ["git"] = wezterm.nerdfonts.fa_git,
    ["go"] = wezterm.nerdfonts.seti_go,
    ["htop"] = wezterm.nerdfonts.mdi_chart_donut_variant,
    ["kubectl"] = wezterm.nerdfonts.linux_docker,
    ["kuberlr"] = wezterm.nerdfonts.linux_docker,
    ["lazydocker"] = wezterm.nerdfonts.linux_docker,
    ["lazygit"] = wezterm.nerdfonts.oct_git_compare,
    ["lua"] = wezterm.nerdfonts.seti_lua,
    ["make"] = wezterm.nerdfonts.seti_makefile,
    ["node"] = wezterm.nerdfonts.mdi_hexagon,
    ["nvim"] = wezterm.nerdfonts.custom_vim,
    ["psql"] = "󱤢",
    ["ruby"] = wezterm.nerdfonts.cod_ruby,
    ["stern"] = wezterm.nerdfonts.linux_docker,
    ["sudo"] = wezterm.nerdfonts.fa_hashtag,
    ["usql"] = "󱤢",
    ["vim"] = wezterm.nerdfonts.dev_vim,
    ["wget"] = wezterm.nerdfonts.mdi_arrow_down_box,
    ["zsh"] = wezterm.nerdfonts.dev_terminal,
}

-- Return the Tab's current working directory
local function get_cwd(tab)
    return tab.active_pane.current_working_dir.file_path or ""
end

-- Remove all path components and return only the last value
local function remove_abs_path(path) return path:gsub("(.*[/\\])(.*)", "%2") end

-- Return the pretty path of the tab's current working directory
local function get_display_cwd(tab)
    local current_dir = get_cwd(tab)
    local HOME_DIR = string.format("file://%s", os.getenv("HOME"))
    return current_dir == HOME_DIR and "~/" or remove_abs_path(current_dir)
end

-- Return the concise name or icon of the running process for display
local function get_process(tab)
    if not tab.active_pane or tab.active_pane.foreground_process_name == "" then return "[?]" end

    local process_name = remove_abs_path(tab.active_pane.foreground_process_name)
    if process_name:find("kubectl") then process_name = "kubectl" end

    return process_icons[process_name] or string.format("[%s]", process_name)
end

-- Pretty format the tab title
local function format_title(tab)
    local cwd = get_display_cwd(tab)
    local process = get_process(tab)

    local active_title = tab.active_pane.title
    if active_title:find("- NVIM") then active_title = active_title:gsub("^([^ ]+) .*", "%1") end

    local description = (not active_title or active_title == cwd) and "~" or active_title
    return string.format(" %s %s/ %s ", process, cwd, description)
end

-- Determine if a tab has unseen output since last visited
local function has_unseen_output(tab)
    if not tab.is_active then
        for _, pane in ipairs(tab.panes) do
            if pane.has_unseen_output then return true end
        end
    end
    return false
end

-- Returns manually set title (from `tab:set_title()` or `wezterm cli set-tab-title`) or creates a new one
local function get_tab_title(tab)
    local title = tab.tab_title
    if title and #title > 0 then return title end
    return format_title(tab)
end

-- Convert arbitrary strings to a unique hex color value
-- Based on: https://stackoverflow.com/a/3426956/3219667
local function string_to_color(str)
    -- Convert the string to a unique integer
    local hash = 0
    for i = 1, #str do
        hash = string.byte(str, i) + ((hash << 5) - hash)
    end

    -- Convert the integer to a unique color
    local c = string.format("%06X", hash & 0x00FFFFFF)
    return "#" .. (string.rep("0", 6 - #c) .. c):upper()
end

local function select_contrasting_fg_color(hex_color)
    -- Note: this could use `return color:complement_ryb()` instead if you prefer or other builtins!

    local color = wezterm.color.parse(hex_color)
    ---@diagnostic disable-next-line: unused-local
    local lightness, _a, _b, _alpha = color:laba()
    if lightness > 55 then
        return "#000000" -- Black has higher contrast with colors perceived to be "bright"
    end
    return "#FFFFFF" -- White has higher contrast
end

-- Inline tests
local testColor = string_to_color("/Users/kyleking/Developer/ProjectA")
assert(testColor == "#EBD168", "Unexpected color value for test hash (" .. testColor .. ")")
assert(select_contrasting_fg_color("#494CED") == "#FFFFFF", "Expected higher contrast with white")
assert(select_contrasting_fg_color("#128b26") == "#FFFFFF", "Expected higher contrast with white")
assert(select_contrasting_fg_color("#58f5a6") == "#000000", "Expected higher contrast with black")
assert(select_contrasting_fg_color("#EBD168") == "#000000", "Expected higher contrast with black")

-- On format tab title events, override the default handling to return a custom title
-- Docs: https://wezfurlong.org/wezterm/config/lua/window-events/format-tab-title.html
---@diagnostic disable-next-line: unused-local
wezterm.on("format-tab-title", function(tab, tabs, panes, config, hover, max_width)
    local title = get_tab_title(tab)
    local color = string_to_color(get_cwd(tab))

    if tab.is_active then
        return {
            { Attribute = { Intensity = "Bold" } },
            { Background = { Color = color } },
            { Foreground = { Color = select_contrasting_fg_color(color) } },
            { Text = title },
        }
    end
    if has_unseen_output(tab) then
        return {
            { Foreground = { Color = "#EBD168" } },
            { Text = title },
        }
    end
    return title
end)

The full file is here: https://github.com/KyleKing/dotfiles/blob/39d1634456ad978f6aa59c8229a6194c02113499/dot_wezterm.lua

Update: based on @wez's advice, I've updated the function to use Wezterm's built-in color logic!

[wez]

Neat! For the color math, consider using:

• https://wezfurlong.org/wezterm/config/lua/wezterm.color/parse.html to parse the color
• https://wezfurlong.org/wezterm/config/lua/color/hsla.html to get the luminance

You could get more thorough or exotic by using the other color functions:

• https://wezfurlong.org/wezterm/config/lua/color/contrast_ratio.html
• https://wezfurlong.org/wezterm/config/lua/color/complement_ryb.html
• or the others at https://wezfurlong.org/wezterm/config/lua/color/index.html

[ro0gr]

Great, Exactly what I was looking for! Thank you for sharing!