feat(perf): Skip parsing when no text changes and in already parsed range

# Details

Issue: #115

After the change to parse only the visible range of a file along with
a debounce there was a performance degredation for simple cursor movements.

This is because cursor movements no longer had the benefit of using
cached marks, so are re-computed and feed into the same debounced method.
This can cause laggy behavior.

To fix this I have added back the caching behavior from before with some
updates to account for the new logic. Like before marks will not be parsed
for events that do not update the text. In addition to the simple event
check we also need to validate that the range of cached marks accounts
for everything in the users viewport, otherwise we still need to parse.

This should have the benefits of the snappy behavior from before along with
being able to handle essentially arbitrary file sizes. Have increased the
default max file size to 10MB since performance impact is minimal.

Author: MeanderingProgrammer

README.md

@@ -124,7 +124,7 @@ require('render-markdown').setup({
     enabled = true,
     -- Maximum file size (in MB) that this plugin will attempt to render
     -- Any file larger than this will effectively be ignored
-    max_file_size = 1.5,
+    max_file_size = 10.0,
     -- Milliseconds that must pass before updating marks, updates occur
     -- within the context of the visible window, not the entire buffer
     debounce = 100,

benches/medium_spec.lua

@@ -5,13 +5,13 @@ local util = require('benches.util')
 describe('medium.md', function()
     it('default', function()
         local base_marks = 46
-        util.between(20, 30, util.setup('temp/medium.md'))
+        util.less_than(util.setup('temp/medium.md'), 30)
         util.num_marks(base_marks)
 
-        util.between(0, 5, util.move_down(3))
+        util.less_than(util.move_down(3), 0.5)
         util.num_marks(base_marks + 2)
 
-        util.between(1, 15, util.insert_mode())
+        util.less_than(util.insert_mode(), 15)
         util.num_marks(base_marks + 2)
     end)
 end)

benches/medium_table_spec.lua

@@ -5,13 +5,13 @@ local util = require('benches.util')
 describe('medium-table.md', function()
     it('default', function()
         local base_marks = 468
-        util.between(80, 105, util.setup('temp/medium-table.md'))
+        util.less_than(util.setup('temp/medium-table.md'), 105)
         util.num_marks(base_marks)
 
-        util.between(1, 20, util.move_down(1))
+        util.less_than(util.move_down(1), 0.5)
         util.num_marks(base_marks + 2)
 
-        util.between(5, 30, util.insert_mode())
+        util.less_than(util.insert_mode(), 25)
         util.num_marks(base_marks + 2)
     end)
 end)

benches/readme_spec.lua

@@ -5,13 +5,13 @@ local util = require('benches.util')
 describe('README.md', function()
     it('default', function()
         local base_marks = 55
-        util.between(30, 50, util.setup('README.md'))
+        util.less_than(util.setup('README.md'), 50)
         util.num_marks(base_marks)
 
-        util.between(1, 5, util.move_down(1))
+        util.less_than(util.move_down(1), 0.5)
         util.num_marks(base_marks + 2)
 
-        util.between(10, 20, util.insert_mode())
+        util.less_than(util.insert_mode(), 20)
         util.num_marks(base_marks + 2)
     end)
 end)

benches/util.lua

@@ -50,11 +50,10 @@ function M.feed(keys)
     vim.api.nvim_feedkeys(escape, 'nx', false)
 end
 
----@param low integer
----@param high integer
 ---@param actual number
-function M.between(low, high, actual)
-    truthy(actual > low and actual < high, string.format('expected %d < %f < %d', low, actual, high))
+---@param max number
+function M.less_than(actual, max)
+    truthy(actual < max, string.format('expected %f < %f', actual, max))
 end
 
 ---@param expected integer

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*          For 0.10.0          Last change: 2024 August 02
+*render-markdown.txt*          For 0.10.0          Last change: 2024 August 04
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*
@@ -157,7 +157,7 @@ Full Default Configuration ~
         enabled = true,
         -- Maximum file size (in MB) that this plugin will attempt to render
         -- Any file larger than this will effectively be ignored
-        max_file_size = 1.5,
+        max_file_size = 10.0,
         -- Milliseconds that must pass before updating marks, updates occur
         -- within the context of the visible window, not the entire buffer
         debounce = 100,

lua/render-markdown/buffer_state.lua

@@ -3,6 +3,7 @@
 ---@field private timer uv_timer_t
 ---@field private running boolean
 ---@field state? 'default'|'rendered'
+---@field marks? render.md.Extmark[]
 local BufferState = {}
 BufferState.__index = BufferState
 
@@ -14,18 +15,19 @@ function BufferState.new(buf)
     self.timer = (vim.uv or vim.loop).new_timer()
     self.running = false
     self.state = nil
+    self.marks = nil
     return self
 end
 
 ---@param ms integer
----@param cb fun(buf: integer)
-function BufferState:debounce(ms, cb)
+---@param callback fun()
+function BufferState:debounce(ms, callback)
     self.timer:start(ms, 0, function()
         self.running = false
     end)
     if not self.running then
         self.running = true
-        vim.schedule_wrap(cb)(self.buf)
+        vim.schedule(callback)
     end
 end
 

lua/render-markdown/context.lua

@@ -3,7 +3,6 @@
 ---@field private win integer
 ---@field private top integer
 ---@field private bottom integer
----@field private conceallevel integer
 ---@field private conceal? table<integer, [integer, integer][]>
 ---@field private links table<integer, [integer, integer, string][]>
 local Context = {}
@@ -12,15 +11,16 @@ Context.__index = Context
 ---@param buf integer
 ---@param win integer
 ---@param offset integer
+---@return render.md.Context
 function Context.new(buf, win, offset)
     local self = setmetatable({}, Context)
     self.buf = buf
     self.win = win
     local top = vim.api.nvim_win_call(win, vim.fn.winsaveview).topline - 1
     local height = vim.api.nvim_win_get_height(win)
+    local lines = vim.api.nvim_buf_line_count(buf)
     self.top = math.max(top - offset, 0)
-    self.bottom = top + height + offset
-    self.conceallevel = vim.api.nvim_get_option_value('conceallevel', { scope = 'local', win = win })
+    self.bottom = math.min(top + height + offset, lines)
     self.conceal = nil
     self.links = {}
     return self
@@ -47,6 +47,12 @@ function Context:get_width()
     return vim.api.nvim_win_get_width(self.win)
 end
 
+---@param other render.md.Context
+---@return boolean
+function Context:contains_range(other)
+    return self.top <= other.top and self.bottom >= other.bottom
+end
+
 ---@return Range2
 function Context:range()
     return { self.top, self.bottom }
@@ -82,7 +88,8 @@ end
 ---@private
 ---@return table<integer, [integer, integer][]>
 function Context:compute_conceal()
-    if self.conceallevel == 0 then
+    local conceallevel = vim.api.nvim_get_option_value('conceallevel', { scope = 'local', win = self.win })
+    if conceallevel == 0 then
         return {}
     end
     local ranges = {}
@@ -137,6 +144,17 @@ function M.reset(buf, win)
     cache[buf] = Context.new(buf, win, 10)
 end
 
+---@param buf integer
+---@param win integer
+---@return boolean
+function M.contains_range(buf, win)
+    local context = cache[buf]
+    if context == nil then
+        return false
+    end
+    return context:contains_range(Context.new(buf, win, 0))
+end
+
 ---@param buf integer
 ---@return render.md.Context
 function M.get(buf)

lua/render-markdown/extmark.lua

@@ -0,0 +1,76 @@
+---@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
+---@return render.md.Extmark
+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 config render.md.BufferConfig
+---@param row? integer
+function Extmark:render(config, row)
+    if self:should_show(config, row) then
+        self:show()
+    else
+        self:hide()
+    end
+end
+
+---@private
+function Extmark:show()
+    if self.id == nil then
+        self.mark.opts.strict = false
+        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
+
+---@private
+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 config render.md.BufferConfig
+---@param row? integer
+---@return boolean
+function Extmark:should_show(config, row)
+    -- Anti-conceal is not enabled -> all marks should be shown
+    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_inline.lua

@@ -71,7 +71,7 @@ function M.shortcut(config, buf, info)
     if checkbox ~= nil then
         return M.checkbox(config, info, checkbox)
     end
-    local line = vim.api.nvim_buf_get_lines(buf, info.start_row, info.start_row + 1, true)[1]
+    local line = vim.api.nvim_buf_get_lines(buf, info.start_row, info.start_row + 1, false)[1]
     if line:find('[' .. info.text .. ']', 1, true) ~= nil then
         return M.wiki_link(config, info)
     end