Neoscroll: a smooth scrolling neovim plugin written in lua

Demo

demo.mp4

Features

• Smooth scrolling for window movement commands (mappings optional): <C-u>, <C-d>, <C-b>, <C-f>, <C-y>, <C-e>, zt, zz, zb.
• Takes into account folds.
• A single scrolling function that accepts either the number of lines or the percentage of the window to scroll.
• Cursor is hidden while scrolling (optional) for a more pleasing scrolling experience.
• Customizable scrolling behaviour.
• You can use predefined easing functions for the scrolling animation.
• Performance mode that turns off syntax highlighting while scrolling for slower machines or files with heavy regex syntax highlighting.
• Cancel scroll by scrolling in the opposite direction.
• Simulated "stop on key release" when holding down a key to scroll.

Installation

You will need neovim 0.5 for this plugin to work. Install it using your favorite plugin manager:

• With Packer: use 'karb94/neoscroll.nvim'

• With vim-plug: Plug 'karb94/neoscroll.nvim'

IMPORTANT: Neoscroll uses the value of the scrolloff option to behave as expected. If the local scope of this variable is not explicitly set it will store a garbage random value instead of inheriting the global value of the option. This is a reported Neovim bug. Therefore Neoscroll will use the global scrolloff value by default. If you want Neoscroll to use the local scrolloff value then set the Neoscroll option use_local_scrolloff to true but make sure you set the local scrolloff explicitly either in you init file or at runtime.

Quickstart

Add the setup() function to your init file.

For init.lua:

require('neoscroll').setup()

For init.vim:

lua require('neoscroll').setup()

Options

Setup function with all the options and their default values:

require('neoscroll').setup({
    -- All these keys will be mapped to their corresponding default scrolling animation
    mappings = {'<C-u>', '<C-d>', '<C-b>', '<C-f>',
                '<C-y>', '<C-e>', 'zt', 'zz', 'zb'},
    hide_cursor = true,          -- Hide cursor while scrolling
    stop_eof = true,             -- Stop at <EOF> when scrolling downwards
    use_local_scrolloff = false, -- Use the local scope of scrolloff instead of the global scope
    respect_scrolloff = false,   -- Stop scrolling when the cursor reaches the scrolloff margin of the file
    cursor_scrolls_alone = true, -- The cursor will keep on scrolling even if the window cannot scroll further
    easing_function = nil,       -- Default easing function
    pre_hook = nil,              -- Function to run before the scrolling animation starts
    post_hook = nil,             -- Function to run after the scrolling animation ends
    performance_mode = false,    -- Disable "Performance Mode" on all buffers.
})

Custom mappings

You can create your own scrolling mappings using the following lua functions:

• scroll(lines, move_cursor, time[, easing])
• zt(half_win_time[, easing])
• zz(half_win_time[, easing])
• zb(half_win_time[, easing])

Read the documentation for more details on how to use each function.

You can use the following syntactic sugar in your init.lua to define lua function mappings in normal, visual and select modes:

require('neoscroll').setup({
    -- Set any options as needed
})

local t = {}
-- Syntax: t[keys] = {function, {function arguments}}
t['<C-u>'] = {'scroll', {'-vim.wo.scroll', 'true', '250'}}
t['<C-d>'] = {'scroll', { 'vim.wo.scroll', 'true', '250'}}
t['<C-b>'] = {'scroll', {'-vim.api.nvim_win_get_height(0)', 'true', '450'}}
t['<C-f>'] = {'scroll', { 'vim.api.nvim_win_get_height(0)', 'true', '450'}}
t['<C-y>'] = {'scroll', {'-0.10', 'false', '100'}}
t['<C-e>'] = {'scroll', { '0.10', 'false', '100'}}
t['zt']    = {'zt', {'250'}}
t['zz']    = {'zz', {'250'}}
t['zb']    = {'zb', {'250'}}

require('neoscroll.config').set_mappings(t)

Easing functions

By default the scrolling animation has a constant speed, i.e. the time between each line scroll is constant. If you want to smooth the start and/or end of the scrolling animation you can pass the name of one of the easing functions that Neoscroll provides to the scroll() function. You can use any of the following easing functions: quadratic, cubic, quartic, quintic, circular, sine. Neoscroll will then adjust the time between each line scroll using the selected easing function. This dynamic time adjustment can make animations more pleasing to the eye.

To learn more about easing functions here are some useful links:

• Microsoft documentation
• easings.net
• febucci.com

Examples

Using the same syntactic sugar introduced in Custom mappings we can write the following config:

require('neoscroll').setup({
    easing_function = "quadratic" -- Default easing function
    -- Set any other options as needed
})

local t = {}
-- Syntax: t[keys] = {function, {function arguments}}
-- Use the "sine" easing function
t['<C-u>'] = {'scroll', {'-vim.wo.scroll', 'true', '350', [['sine']]}}
t['<C-d>'] = {'scroll', { 'vim.wo.scroll', 'true', '350', [['sine']]}}
-- Use the "circular" easing function
t['<C-b>'] = {'scroll', {'-vim.api.nvim_win_get_height(0)', 'true', '500', [['circular']]}}
t['<C-f>'] = {'scroll', { 'vim.api.nvim_win_get_height(0)', 'true', '500', [['circular']]}}
-- Pass "nil" to disable the easing animation (constant scrolling speed)
t['<C-y>'] = {'scroll', {'-0.10', 'false', '100', nil}}
t['<C-e>'] = {'scroll', { '0.10', 'false', '100', nil}}
-- When no easing function is provided the default easing function (in this case "quadratic") will be used
t['zt']    = {'zt', {'300'}}
t['zz']    = {'zz', {'300'}}
t['zb']    = {'zb', {'300'}}

require('neoscroll.config').set_mappings(t)

pre_hook and post_hook functions

Set pre_hook and post_hook functions to run custom code before and/or after the scrolling animation. The function will be called with the info parameter which can be optionally passed to scroll() (or any of the provided wrappers). This can be used to conditionally run different hooks for different types of scrolling animations.

For example, if you want to hide the cursorline only for <C-d>/<C-u> scrolling animations you can do something like this:

require('neoscroll').setup({
    pre_hook = function(info) if info == "cursorline" then vim.wo.cursorline = false end end,
    post_hook = function(info) if info == "cursorline" then vim.wo.cursorline = true end end
})
local t = {}
t['<C-u>'] = { 'scroll', { '-vim.wo.scroll', 'true', '350', 'sine', [['cursorline']] } }
t['<C-d>'] = { 'scroll', {  'vim.wo.scroll', 'true', '350', 'sine', [['cursorline']] } }
require('neoscroll.config').set_mappings(t)

Keep in mind that the info variable is not restricted to a string. It can also be a table with multiple key-pair values.

Known issues

• Because of a Neovim bug Neoscroll has to use the global scrolloff value by default. Related issues: #11 and #28. Read the IMPORTANT note under the Installation section.
• <C-u>, <C-d>, <C-b>, <C-f> mess up macros (issue).

Acknowledgements

This plugin was inspired by vim-smoothie and neo-smooth-scroll.nvim. Big thank you to their authors!