Minimal example of using possession.nvim with alpha.nvim

possession_alpha_example.lua

-- HELPER FUNCTIONS --

-- https://github.com/goolord/alpha-nvim/blob/8a1477d8b99a931530f3cfb70f6805b759bebbf7/lua/alpha/themes/startify.lua#L28
local leader = 'SPC'
local function create_button(sc, txt, keybind, keybind_opts)
    local sc_ = sc:gsub("%s", ""):gsub(leader, "<leader>")

    local opts = {
        position = "left",
        shortcut = "[" .. sc .. "] ",
        cursor = 1,
        -- width = 50,
        align_shortcut = "left",
        hl_shortcut = { { "Operator", 0, 1 }, { "Number", 1, #sc + 1 }, { "Operator", #sc + 1, #sc + 2 } },
        shrink_margin = false,
    }
    if keybind then
        keybind_opts = vim.F.if_nil(keybind_opts, { noremap = true, silent = true, nowait = true })
        opts.keymap = { "n", sc_, keybind, { noremap = false, silent = true, nowait = true } }
    end

    local function on_press()
        -- local key = vim.api.nvim_replace_termcodes(keybind .. "<Ignore>", true, false, true)
        local key = vim.api.nvim_replace_termcodes(sc .. "<Ignore>", true, false, true)
        vim.api.nvim_feedkeys(key, "t", false)
    end

    return {
        type = "button",
        val = txt,
        on_press = on_press,
        opts = opts,
    }
end

local function pad_right(str, width)
    return str .. string.rep(' ', math.max(0, width - vim.fn.strdisplaywidth(str)))
end

-- Recursively traverse layout and modify all elements to be properly
-- centered to given width. This is a hacky way of achieving centering, see:
-- https://github.com/goolord/alpha-nvim/issues/18#issuecomment-991822664
local center_layout
center_layout = function(layout, width)
    local pad = function(str)
        return pad_right(str, width)
    end
    local wrap_fn = function(fn)
        return function()
            local val = fn()
            center_layout(val, width)
            return val
        end
    end
    for _, el in ipairs(layout) do
        if el.type == 'button' then
            el.opts = el.opts or {}
            el.opts.position = 'center'
            el.opts.width = width
        elseif el.type == 'text' then
            el.opts = el.opts or {}
            el.opts.position = 'center'
            if type(el.val) == 'table' then
                el.val = vim.tbl_map(pad, el.val)
            else
                el.val = pad(el.val)
            end
        elseif el.type == 'group' then
            if type(el.val) == 'function' then
                el.val = wrap_fn(el.val)
            else
                center_layout(el.val, width)
            end
        end
    end
end

-- Smart top padding
local top_padding = function(height_estimate)
    local cached
    return function()
        -- Use cached value if redrawing from another window
        local filetype = vim.api.nvim_buf_get_option(0, 'filetype')
        if cached and filetype ~= 'alpha' then
            return cached
        end
        local height = vim.api.nvim_win_get_height(0)
        local calculated = (height - height_estimate) / 2
        cached = math.ceil(math.max(1, calculated))
        return cached
    end
end

-- LAYOUT DEFINITION --

local query = require('possession.query')

local workspaces = {
    {
        'Workspace A',  -- title
        'a',            -- shortcuts prefix
        {
            '/root/directory/a',
            '/other/root/directory/',
        },
    },
    {
        'Workspace B',
        'b',
        '/root/directory/b',
    }
}
local get_layout = function()
    return query.alpha_workspace_layout(workspaces, create_button, {
        others_name = 'Sessions Without Workspace',
    })
end

-- use with the rest of sections for alpha.nvim, with throttling to avoid reading files on each redraw
local utils = require('possession.utils')
local layout = {
    { type = 'padding', val = top_padding(50) },
    { -- top buttons
        type = 'group',
        val = {
            create_button('e', 'New file', '<cmd>enew<cr>'),
        },
    },
    { type = 'padding', val = 1 },
    { -- sessions
        type = 'group',
        val = utils.throttle(get_layout, 5000),
    },
    { type = 'padding', val = 1 },
    { -- bottom buttons
        type = 'group',
        val = {
            create_button('q', 'Quit', '<cmd>quit<cr>')
        },
    },
    { type = 'group', val = {} }, -- footer
}

center_layout(layout, 86)

require('alpha').setup {
    layout = layout,
    opts = {},
}