Neoscroll: a smooth scrolling neovim plugin written in lua

Demo

https://user-images.githubusercontent.com/41967813/121818668-7b36c800-cc80-11eb-8c3a-45a4767b8f05.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.
• Scroll any window.
• 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.
• Scroll any window by window-ID

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'

• With lazy.nvim, create the file ~/.config/nvim/lua/plugins/neoscroll.lua:

  return {
    "karb94/neoscroll.nvim",
    config = function ()
      require('neoscroll').setup({})
    end
  }

Options

Read :help neoscroll-options for a detailed description of all the options.

setup() with all the options and their default values:

require('neoscroll').setup({
  mappings = {                 -- Keys to be mapped to their corresponding default scrolling animation
    '<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
  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 = 'linear',           -- 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.
  ignored_events = {           -- Events ignored while scrolling
      'WinScrolled', 'CursorMoved'
  },
})

You can map a smaller set of default mappings:

require('neoscroll').setup({ mappings = {'<C-u>', '<C-d>', '<C-b>', '<C-f>'} })

Or you can disable all default mappings by passing an empty list:

require('neoscroll').setup({ mappings = {} })

The section below explains how to create your own custom mappings.

Custom mappings

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

• scroll(lines, opts)
• ctrl_u
• ctrl_d
• ctrl_b
• ctrl_f
• zt(opts)
• zz(opts)
• zb(opts)

Read :help neoscroll.scroll() and :help neoscroll-helper-functions for more details.

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

neoscroll = require('neoscroll')
local keymap = {
  ["<C-u>"] = function() neoscroll.ctrl_u({ duration = 250 }) end;
  ["<C-d>"] = function() neoscroll.ctrl_d({ duration = 250 }) end;
  ["<C-b>"] = function() neoscroll.ctrl_b({ duration = 450 }) end;
  ["<C-f>"] = function() neoscroll.ctrl_f({ duration = 450 }) end;
  ["<C-y>"] = function() neoscroll.scroll(-0.1, { move_cursor=false; duration = 100 }) end;
  ["<C-e>"] = function() neoscroll.scroll(0.1, { move_cursor=false; duration = 100 }) end;
  ["zt"]    = function() neoscroll.zt({ half_win_duration = 250 }) end;
  ["zz"]    = function() neoscroll.zz({ half_win_duration = 250 }) end;
  ["zb"]    = function() neoscroll.zb({ half_win_duration = 250 }) end;
}
local modes = { 'n', 'v', 'x' }
for key, func in pairs(keymap) do
  vim.keymap.set(modes, key, func)
end

Easing functions

By default the scrolling animation has a constant speed (linear), i.e. the time between each line scroll is constant. If you want to smooth the start and 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: linear, 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:

neoscroll = require('neoscroll')
neoscroll.setup({
  -- Default easing function used in any animation where
  -- the `easing` argument has not been explicitly supplied
  easing = "quadratic"
})
local keymap = {
  -- Use the "sine" easing function
  ["<C-u>"] = function() neoscroll.ctrl_u({ duration = 250; easing = 'sine' }) end;
  ["<C-d>"] = function() neoscroll.ctrl_d({ duration = 250; easing = 'sine' }) end;
  -- Use the "circular" easing function
  ["<C-b>"] = function() neoscroll.ctrl_b({ duration = 450; easing = 'circular' }) end;
  ["<C-f>"] = function() neoscroll.ctrl_f({ duration = 450; easing = 'circular' }) end;
  -- When no value is passed the `easing` option supplied in `setup()` is used
  ["<C-y>"] = function() neoscroll.scroll(-0.1, { move_cursor=false; duration = 100 }) end;
  ["<C-e>"] = function() neoscroll.scroll(0.1, { move_cursor=false; duration = 100 }) end;
}
local modes = { 'n', 'v', 'x' }
for key, func in pairs(keymap) do
    vim.keymap.set(modes, key, func)
end

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 keymap = {
  ["<C-u>"] = function() neoscroll.ctrl_u({ duration = 250; info = 'cursorline' }) end;
  ["<C-d>"] = function() neoscroll.ctrl_d({ duration = 250; info = 'cursorline' }) end;
}
local modes = { 'n', 'v', 'x' }
for key, func in pairs(keymap) do
  vim.keymap.set(modes, key, func)
end

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

• <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!