feat(nvim): smooth scrolling plugin

1 files changed, 35 insertions, 0 deletions

diff --git a/plugin/50-smooth_scroll.lua b/plugin/50-smooth_scroll.lua
new file mode 100644
index 0000000..84824a3
--- /dev/null
+++ b/plugin/50-smooth_scroll.lua
@@ -0,0 +1,35 @@
+local Dir = {
+	UP = 1,
+	DOWN = 2,
+}
+
+local function smooth_scroll(dir)
+	local view, start_pos, buf_line_count, win_height =
+		vim.fn.winsaveview(),
+		vim.api.nvim_win_get_cursor(0),
+		vim.api.nvim_buf_line_count(0),
+		vim.api.nvim_win_get_height(0)
+	local duration, sleep_duration = 100, 16 -- 60 fps
+	local max_distance = dir == Dir.DOWN and buf_line_count - start_pos[1] or start_pos[1] - 1
+	local distance = math.min(max_distance, math.floor(win_height / 2))
+	local steps_number = math.ceil(duration / sleep_duration) -- We want a movement every `sleep_duration` msec
+	local step = distance / steps_number
+	for i = 1, steps_number do
+		vim.defer_fn(function()
+			local offset = math.ceil(step * i) * (dir == Dir.DOWN and 1 or -1)
+			local new_pos = { start_pos[1] + offset, start_pos[2] }
+			vim.api.nvim_win_set_cursor(0, new_pos)
+			local new_topline = math.max(1, view.topline + offset)
+			if buf_line_count - new_topline >= win_height then -- don't move viewport beyond eof (DOWN) or first line (UP)
+				vim.fn.winrestview({ lnum = view.lnum + offset, topline = new_topline }) -- move viewport
+			end
+		end, sleep_duration * i)
+	end
+end
+
+vim.api.nvim_create_user_command("ScrollSmoothDown", function()
+	smooth_scroll(Dir.DOWN)
+end, { desc = "Scroll down smoothly" })
+vim.api.nvim_create_user_command("ScrollSmoothUp", function()
+	smooth_scroll(Dir.UP)
+end, { desc = "Scroll up smoothly" })