From 6764c57a44362da5ce0bf142f996c45e63b0a581 Mon Sep 17 00:00:00 2001
From: Hiroshi Shirosaki <h.shirosaki@gmail.com>
Date: Fri, 8 Jan 2016 20:41:57 +0900
Subject: [PATCH 1/1] Improve performance of folding

Folding is very slow for large files.
Drop `s:effective_line()` to reduce call of `s:is_mkdCode()`.
---
 after/ftplugin/markdown.vim | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/after/ftplugin/markdown.vim b/after/ftplugin/markdown.vim
index 1d0572c..d965a71 100644
--- a/after/ftplugin/markdown.vim
+++ b/after/ftplugin/markdown.vim
@@ -10,24 +10,19 @@ function! s:is_mkdCode(lnum)
     return synIDattr(synID(a:lnum, 1, 0), 'name') == 'mkdCode'
 endfunction
 
-function! s:effective_line(lnum)
-    let line = getline(a:lnum)
-    return (line !~ '^[=-#]' || s:is_mkdCode(a:lnum)) ? '' : line
-endfunction
-
 if get(g:, "vim_markdown_folding_style_pythonic", 0)
     function! Foldexpr_markdown(lnum)
-        let l2 = s:effective_line(a:lnum+1)
-        if  l2 =~ '^==\+\s*'
+        let l2 = getline(a:lnum+1)
+        if  l2 =~ '^==\+\s*' && !s:is_mkdCode(a:lnum+1)
             " next line is underlined (level 1)
             return '>0'
-        elseif l2 =~ '^--\+\s*'
+        elseif l2 =~ '^--\+\s*' && !s:is_mkdCode(a:lnum+1)
             " next line is underlined (level 2)
             return '>1'
         endif
 
-        let l1 = s:effective_line(a:lnum)
-        if l1 =~ '^#'
+        let l1 = getline(a:lnum)
+        if l1 =~ '^#' && !s:is_mkdCode(a:lnum)
             " current line starts with hashes
             return '>'.(matchend(l1, '^#\+') - 1)
         elseif a:lnum == 1
@@ -52,17 +47,17 @@ if get(g:, "vim_markdown_folding_style_pythonic", 0)
     endfunction
 else
     function! Foldexpr_markdown(lnum)
-        let l2 = s:effective_line(a:lnum+1)
-        if  l2 =~ '^==\+\s*'
+        let l2 = getline(a:lnum+1)
+        if  l2 =~ '^==\+\s*' && !s:is_mkdCode(a:lnum+1)
             " next line is underlined (level 1)
             return '>1'
-        elseif l2 =~ '^--\+\s*'
+        elseif l2 =~ '^--\+\s*' && !s:is_mkdCode(a:lnum+1)
             " next line is underlined (level 2)
             return '>2'
         endif
 
-        let l1 = s:effective_line(a:lnum)
-        if l1 =~ '^#'
+        let l1 = getline(a:lnum)
+        if l1 =~ '^#' && !s:is_mkdCode(a:lnum)
             " don't include the section title in the fold
             return '-1'
         endif
@@ -70,9 +65,9 @@ else
         if (a:lnum == 1)
             let l0 = ''
         else
-            let l0 = s:effective_line(a:lnum-1)
+            let l0 = getline(a:lnum-1)
         endif
-        if l0 =~ '^#'
+        if l0 =~ '^#' && !s:is_mkdCode(a:lnum-1)
             " current line starts with hashes
             return '>'.matchend(l0, '^#\+')
         else
-- 
2.39.5