From 98eaab239d5e5bfcf7449086f8d840a0a5f320e3 Mon Sep 17 00:00:00 2001
From: wongxy <xiyao.wong@foxmail.com>
Date: Fri, 15 Apr 2022 12:09:19 +0800
Subject: [PATCH] improve: remove unnecessary caches, use timer for TextChanged

---
 plugin/virt-column.lua | 80 ++++++++++++++++++++----------------------
 1 file changed, 39 insertions(+), 41 deletions(-)

diff --git a/plugin/virt-column.lua b/plugin/virt-column.lua
index f478495..1b4d539 100644
--- a/plugin/virt-column.lua
+++ b/plugin/virt-column.lua
@@ -1,7 +1,6 @@
 --- vim.g.virtcolumn_char: ▕ by default
 
 local api = vim.api
-local fn = vim.fn
 local ffi = require "ffi"
 
 ffi.cdef "int curwin_col_off(void);"
@@ -10,35 +9,20 @@ local curwin_col_off = ffi.C.curwin_col_off
 
 local NS = api.nvim_create_namespace "virt-column"
 
-local function _refresh()
-    local bufnr = api.nvim_get_current_buf()
-    if not api.nvim_buf_is_loaded(bufnr) then
-        return
-    end
-
-    local virtcolumn = vim.b.virtcolumn or vim.w.virtcolumn
-
-    local local_cc = vim.wo.cc
-    if not virtcolumn or local_cc ~= "" then
-        virtcolumn = local_cc
-        vim.wo.cc = ""
-    end
-
-    vim.b.virtcolumn = virtcolumn
-    vim.w.virtcolumn = virtcolumn
-
+---@param cc string
+---@return number[]
+local function parse_items(cc)
+    local textwidth = vim.o.textwidth
     ---@type number[]
     local items = {}
-
-    local textwidth = vim.opt.textwidth:get()
-    for _, c in ipairs(vim.split(virtcolumn, ",")) do
+    for _, c in ipairs(vim.split(cc, ",")) do
         local item
         if c and c ~= "" then
             if vim.startswith(c, "+") then
                 if textwidth ~= 0 then
                     item = textwidth + tonumber(c:sub(2))
                 end
-            elseif vim.startswith(virtcolumn, "-") then
+            elseif vim.startswith(cc, "-") then
                 if textwidth ~= 0 then
                     item = textwidth - tonumber(c:sub(2))
                 end
@@ -53,21 +37,38 @@ local function _refresh()
     table.sort(items, function(a, b)
         return a > b
     end)
+    return items
+end
 
-    api.nvim_buf_clear_namespace(bufnr, NS, 0, -1)
+local function _refresh()
+    local curbuf = api.nvim_get_current_buf()
+    if not api.nvim_buf_is_loaded(curbuf) then
+        return
+    end
+
+    local items = vim.b.virtcolumn_items or vim.w.virtcolumn_items
+    local local_cc = vim.wo.cc
+    if not items or local_cc ~= "" then
+        items = parse_items(local_cc)
+        vim.wo.cc = ""
+    end
+    vim.b.virtcolumn_items = items
+    vim.w.virtcolumn_items = items
+
+    api.nvim_buf_clear_namespace(curbuf, NS, 0, -1)
 
     if #items == 0 then
         return
     end
 
-    local win_lines = vim.o.lines
+    local debounce = math.floor(api.nvim_win_get_height(0) * 0.6)
     local offset = vim.fn.line "w0"
     -- Avoid flickering caused by winscrolled_timer
-    offset = offset <= win_lines and 1 or offset - win_lines
+    offset = (offset <= debounce and 1 or offset - debounce) - 1 -- convert to 0-based
 
-    --                                                  Avoid flickering caused by winscrolled_timer
-    --                                                                       ↓↓↓↓↓↓↓↓↓↓↓
-    local lines = api.nvim_buf_get_lines(bufnr, offset - 1, vim.fn.line "w$" + win_lines, false)
+    --                                                Avoid flickering caused by winscrolled_timer
+    --                                                                    ↓↓↓↓↓↓↓↓↓↓↓
+    local lines = api.nvim_buf_get_lines(curbuf, offset, vim.fn.line "w$" + debounce, false)
     local width = api.nvim_win_get_width(0) - curwin_col_off()
     local tabstop = vim.opt.tabstop:get()
     local char = vim.g.virtcolumn_char or "▕"
@@ -76,7 +77,7 @@ local function _refresh()
         for _, item in ipairs(items) do
             local line = lines[i]:gsub("\t", string.rep(" ", tabstop))
             if width > item and api.nvim_strwidth(line) < item then
-                api.nvim_buf_set_extmark(bufnr, NS, i + offset - 2, 0, {
+                api.nvim_buf_set_extmark(curbuf, NS, i + offset - 1, 0, {
                     virt_text = { { char, "VirtColumn" } },
                     virt_text_pos = "overlay",
                     hl_mode = "combine",
@@ -88,8 +89,9 @@ local function _refresh()
     end
 end
 
--- Avoid unnecessary refreshing as much as possible
+-- Avoid unnecessary refreshing as much as possible lcoallfdafffadf
 local winscrolled_timer
+local textchanged_timer
 local function refresh(args)
     ---@type string
     local event = args.event or ""
@@ -98,14 +100,13 @@ local function refresh(args)
             winscrolled_timer:stop()
             winscrolled_timer:close()
         end
-        winscrolled_timer = vim.defer_fn(_refresh, 100)
+        winscrolled_timer = vim.defer_fn(_refresh, 150)
     elseif event:match "TextChanged" then
-        local lines_count = fn.line "$"
-        local need_refresh = vim.b.virtcolumn_lines_count ~= lines_count
-        vim.b.virtcolumn_lines_count = lines_count
-        if need_refresh then
-            _refresh()
+        if textchanged_timer and textchanged_timer:is_active() then
+            textchanged_timer:stop()
+            textchanged_timer:close()
         end
+        textchanged_timer = vim.defer_fn(_refresh, 500)
     else
         _refresh()
     end
@@ -119,7 +120,6 @@ local function set_hl()
         vim.cmd [[hi default link VirtColumn NonText]]
     end
 end
-set_hl()
 
 local group = api.nvim_create_augroup("virtcolumn", {})
 api.nvim_create_autocmd({
@@ -130,11 +130,9 @@ api.nvim_create_autocmd({
     "InsertLeave",
     "InsertEnter",
     "FileChangedShellPost",
-}, {
-    group = group,
-    callback = refresh,
-})
+}, { group = group, callback = refresh })
 api.nvim_create_autocmd("OptionSet", { group = group, callback = refresh, pattern = "colorcolumn" })
 api.nvim_create_autocmd("ColorScheme", { group = group, callback = set_hl })
 
+pcall(set_hl)
 pcall(_refresh)