feat(perf): Improve hiding marks under cursor

## Details

Currently on every cursor movement we clear all buffer marks
then add all the marks back one at a time avoiding the ones
at the current cursor position.

Instead what we can do is avoid touching marks that are unaffected,
i.e. all of the ones that remain rendered, render any previously
removed marks, and remove the relevant marks for the current line.

To accomplish this have added an Extmark class that wraps the raw
mark information from our parsers. These marks store the id of the
extmark from the call to nvim_buf_set_extmark. Now when we attempt
to render a mark we check if we should, i.e. is it on the current
row or not.

- If we should render the mark only do it if it does not have an
  id set and then we set the id
- If we should not render the mark only do it if it does have an
  id set and then we unset the id

By doing this we still loop through all the marks but we only touch
marks that change from shown -> hidden or from hidden -> shown.

Other minor changes:

- Rename `request` module to `context`
- Add benchmark for medium table

Author: MeanderingProgrammer

benches/medium_spec.lua

@@ -7,7 +7,7 @@ describe('medium.md', function()
         util.between(25, 75, util.setup('temp/medium.md'))
         util.num_marks(2998)
 
-        util.between(1, 5, util.move_down(3))
+        util.between(0, 1, util.move_down(3))
         util.num_marks(3000)
 
         util.between(25, 50, util.insert_mode())

benches/medium_table_spec.lua

@@ -0,0 +1,16 @@
+---@module 'luassert'
+
+local util = require('benches.util')
+
+describe('medium-table.md', function()
+    it('default', function()
+        util.between(450, 600, util.setup('temp/medium-table.md'))
+        util.num_marks(30012)
+
+        util.between(1, 5, util.move_down(1))
+        util.num_marks(30014)
+
+        util.between(400, 550, util.insert_mode())
+        util.num_marks(30014)
+    end)
+end)

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*           For 0.10.0           Last change: 2024 July 30
+*render-markdown.txt*           For 0.10.0           Last change: 2024 July 31
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*

lua/render-markdown/context.lua

@@ -0,0 +1,87 @@
+local util = require('render-markdown.util')
+
+---@class render.md.ContextCache
+local cache = {
+    ---@type table<integer, table<integer, [integer, integer][]>>
+    conceal = {},
+    ---@type table<integer, table<integer, [integer, integer, string][]>>
+    inline_links = {},
+}
+
+---@class render.md.Context
+local M = {}
+
+---@param buf integer
+function M.reset_buf(buf)
+    cache.conceal[buf] = {}
+    cache.inline_links[buf] = {}
+end
+
+---@param buf integer
+---@param parser vim.treesitter.LanguageTree
+function M.compute_conceal(buf, parser)
+    local ranges = {}
+    if util.get_win(util.buf_to_win(buf), 'conceallevel') > 0 then
+        parser:for_each_tree(function(tree, language_tree)
+            local nodes = M.get_conceal_nodes(buf, language_tree:lang(), tree:root())
+            for _, node in ipairs(nodes) do
+                local row, start_col, _, end_col = node:range()
+                if ranges[row] == nil then
+                    ranges[row] = {}
+                end
+                table.insert(ranges[row], { start_col, end_col })
+            end
+        end)
+    end
+    cache.conceal[buf] = ranges
+end
+
+---@private
+---@param buf integer
+---@param language string
+---@param root TSNode
+---@return TSNode[]
+function M.get_conceal_nodes(buf, language, root)
+    if not vim.tbl_contains({ 'markdown', 'markdown_inline' }, language) then
+        return {}
+    end
+    local query = vim.treesitter.query.get(language, 'highlights')
+    if query == nil then
+        return {}
+    end
+    local nodes = {}
+    for _, node, metadata in query:iter_captures(root, buf) do
+        if metadata.conceal ~= nil then
+            table.insert(nodes, node)
+        end
+    end
+    return nodes
+end
+
+---@param buf integer
+---@param row integer
+---@return [integer, integer][]
+function M.concealed(buf, row)
+    return cache.conceal[buf][row] or {}
+end
+
+---@param buf integer
+---@param info render.md.NodeInfo
+---@param icon string
+function M.add_inline_link(buf, info, icon)
+    local inline_links = cache.inline_links[buf]
+    local row = info.start_row
+    if inline_links[row] == nil then
+        inline_links[row] = {}
+    end
+    table.insert(inline_links[row], { info.start_col, info.end_col, icon })
+end
+
+---@param buf integer
+---@param row integer
+---@return [integer, integer, string][]
+function M.inline_links(buf, row)
+    return cache.inline_links[buf][row] or {}
+end
+
+return M

lua/render-markdown/extmark.lua

@@ -0,0 +1,74 @@
+local state = require('render-markdown.state')
+
+---@class render.md.Extmark
+---@field private namespace integer
+---@field private buf integer
+---@field private mark render.md.Mark
+---@field private id? integer
+local Extmark = {}
+Extmark.__index = Extmark
+
+---@param namespace integer
+---@param buf integer
+---@param mark render.md.Mark
+function Extmark.new(namespace, buf, mark)
+    local self = setmetatable({}, Extmark)
+    self.namespace = namespace
+    self.buf = buf
+    self.mark = mark
+    self.id = nil
+    return self
+end
+
+---@param row? integer
+function Extmark:render(row)
+    if self:should_show(row) then
+        self:show()
+    else
+        self:hide()
+    end
+end
+
+---@private
+function Extmark:show()
+    if self.id == nil then
+        self.id = vim.api.nvim_buf_set_extmark(
+            self.buf,
+            self.namespace,
+            self.mark.start_row,
+            self.mark.start_col,
+            self.mark.opts
+        )
+    end
+end
+
+function Extmark:hide()
+    if self.id ~= nil then
+        vim.api.nvim_buf_del_extmark(self.buf, self.namespace, self.id)
+        self.id = nil
+    end
+end
+
+---Render marks based on anti-conceal behavior and current row
+---@private
+---@param row? integer
+---@return boolean
+function Extmark:should_show(row)
+    -- Anti-conceal is not enabled -> all marks should be shown
+    local config = state.get_config(self.buf)
+    if not config.anti_conceal.enabled then
+        return true
+    end
+    -- Row is not known means buffer is not active -> all marks should be shown
+    if row == nil then
+        return true
+    end
+    -- Mark is not concealable -> mark should always be shown
+    if not self.mark.conceal then
+        return true
+    end
+    -- Show mark if it is not on the current row
+    return self.mark.start_row ~= row
+end
+
+return Extmark

lua/render-markdown/handler/markdown.lua

@@ -1,10 +1,10 @@
 local colors = require('render-markdown.colors')
 local component = require('render-markdown.component')
+local context = require('render-markdown.context')
 local icons = require('render-markdown.icons')
 local list = require('render-markdown.list')
 local logger = require('render-markdown.logger')
 local pipe_table_parser = require('render-markdown.parser.pipe_table')
-local request = require('render-markdown.request')
 local state = require('render-markdown.state')
 local str = require('render-markdown.str')
 local ts = require('render-markdown.ts')
@@ -726,7 +726,7 @@ end
 ---@param info render.md.NodeInfo
 ---@return integer
 function M.concealed(buf, info)
-    local ranges = request.concealed(buf, info.start_row)
+    local ranges = context.concealed(buf, info.start_row)
     if #ranges == 0 then
         return 0
     end
@@ -751,7 +751,7 @@ end
 ---@return integer
 function M.table_visual_offset(buf, info)
     local result = M.concealed(buf, info)
-    local icon_ranges = request.inline_links(buf, info.start_row)
+    local icon_ranges = context.inline_links(buf, info.start_row)
     for _, icon_range in ipairs(icon_ranges) do
         if info.start_col < icon_range[2] and info.end_col > icon_range[1] then
             result = result - str.width(icon_range[3])

lua/render-markdown/handler/markdown_inline.lua

@@ -1,7 +1,7 @@
 local component = require('render-markdown.component')
+local context = require('render-markdown.context')
 local list = require('render-markdown.list')
 local logger = require('render-markdown.logger')
-local request = require('render-markdown.request')
 local state = require('render-markdown.state')
 local str = require('render-markdown.str')
 local ts = require('render-markdown.ts')
@@ -132,7 +132,7 @@ function M.link(config, buf, info)
     if icon == nil then
         return nil
     end
-    request.add_inline_link(buf, info, icon)
+    context.add_inline_link(buf, info, icon)
     ---@type render.md.Mark
     return {
         conceal = true,