customFolding.vim

" config for fold
" highlights: this costum function enable using both the 'indent' folding
"             and the custum '#<==' '#==>' 'Marker' folding
"#<==================================================================== 
"nnoremap <space> @=((foldclosed(line('.')) < 0) ? 'zc' :'zo')<CR>
nnoremap <space> za
set foldenable
"set foldmethod=indent foldignore=
set foldmethod=expr
set foldexpr=MyFold(v:lnum)
"inBlock count the stack depth of my maker pair
let b:inBlock=0
let b:lastLineNum=0
let b:lastLevel=0
let b:lastGoodLine=0
let b:lastGoodBlock=0
let b:startFoldingMark='^\s*.\?#<==*\|^\s*.\?#region'
let b:endFoldingMark='^\s*.\?#=*=>\|^\s*.\?#endregion'
function! MyFold(linenum)
    let linetext = getline(a:linenum)
    let level     = indent(a:linenum)   / &shiftwidth
    "the first line have 0 fold level
    if (a:linenum == 1)
        if linetext =~ b:startFoldingMark
            let b:inBlock = 1
            let b:lastLineNum=a:linenum
            let b:lastGoodLine=0
            let b:lastGoodBlock=0
            let b:lastLevel=level
            return level
        endif
        let b:inBlock=0
        let b:lastInBlock=0
        let b:lastLineNum=a:linenum
        let b:lastGoodLine=0
        let b:lastGoodBlock=b:inBlock
        "echom a:linenum ':' level+b:inBlock '=' level '+' b:inBlock
        let b:lastLevel=level + b:inBlock
        return level + b:inBlock
    endif

    " not calculate from the mid of text
    if ((b:lastLineNum+1) != a:linenum)
        let level     = indent(a:linenum)   / &shiftwidth
        let lastGoodNum = a:linenum-1
        while (lastGoodNum>1 && getline(lastGoodNum) =~? '\v^\s*$' )
        "while (lastGoodNum>1 && foldlevel(lastGoodNum) == -1 )
            "echom '    ' lastGoodNum ': ' foldlevel(lastGoodNum) ' ' lastGoodNum-1 ' : ' foldlevel(lastGoodNum-1)
            let lastGoodNum -= 1
        endwhile
        "echom 'lastGoodNum:' lastGoodNum 'lastGoodLine' b:lastGoodLine 'lastGoodBlock:' b:lastGoodBlock
        if  (foldlevel(lastGoodNum)==-1)
            let b:inBlock=b:lastGoodBlock
            "echom 'recovery inBlock with lastGoodBlock: ' b:inBlock
        else
            let lastlevel = indent(lastGoodNum)   / &shiftwidth
            let lastlinetext = getline(lastGoodNum)
            let lastlinelevel = foldlevel(lastGoodNum)
            if lastlinetext =~ b:startFoldingMark
                let b:inBlock = lastlinelevel - lastlevel + 1
                "echom 'recovery meet startFoldingMark ' b:inBlock
            elseif lastlinetext =~ b:endFoldingMark
                let b:inBlock = lastlinelevel - lastlevel - 1
                "echom 'recovery meet endFoldingMark' b:inBlock
            else
                let b:inBlock = lastlinelevel - lastlevel
            endif
            "echom 'recovery inBlock with line ' lastGoodNum 'to be: ' b:inBlock '=' lastlinelevel '-' lastlevel
        endif
    endif

    "blank lines have undefined fold level
    if getline(a:linenum) =~? '\v^\s*$'
        "echom '(' b:lastLineNum ':' foldlevel(b:lastLineNum) ')' a:linenum ':' -1
        let b:lastLineNum=a:linenum
        let b:lastLevel=-1
        return -1
    endif

    "if next line is a start of new marker block, inBlock ++
    if linetext =~ b:startFoldingMark
        "if b:lastLineNum != a:linenum
            let b:inBlock = b:inBlock + 1
        "endif
        "echom '(' b:lastLineNum ':' foldlevel(b:lastLineNum) ')' a:linenum ':' level '|' b:inBlock '(+=1)'
        let b:lastLineNum=a:linenum
        if (b:lastLevel != -1)
            let b:lastGoodLine=a:linenum
            let b:lastGoodBlock=b:inBlock
        endif
        let b:lastLevel=level + b:inBlock - 1
        return level + b:inBlock - 1
    "if next line is an end of new marker block, inBlock -
    elseif linetext =~ b:endFoldingMark
        let b:inBlock = b:inBlock - 1
        "echom '(' b:lastLineNum ':' foldlevel(b:lastLineNum) ')' a:linenum ':' level+b:inBlock+1 "|" b:inBlock '(-=1)'
        let b:lastLineNum=a:linenum
        "if (b:lastLevel != -1)
            let b:lastGoodLine=a:linenum
            let b:lastGoodBlock=b:inBlock
        "endif
        let b:lastLevel=level + b:inBlock + 1
        return level + b:inBlock + 1
    endif

    "echom '(' b:lastLineNum ':' foldlevel(b:lastLineNum) ')' a:linenum ':' level+b:inBlock '=' level '+' b:inBlock
    let b:lastLineNum=a:linenum
    if (b:lastLevel != -1)
        let b:lastGoodLine=a:linenum
        let b:lastGoodBlock=b:inBlock
    endif
    let b:lastLevel=level + b:inBlock
    return level+b:inBlock
endfunction
" function for debug, leave it
nnoremap <F2> :call Do_debug_folding()<CR>
function Do_debug_folding()
    exec "echom foldlevel(line('.')) b:lastLineNum"
endfunction

set foldcolumn=0
map ,fc :call Set_foldcolumn()<CR>
function Set_foldcolumn()
    if &foldcolumn=="0"
        set foldcolumn=3
            echo "foldcolumn set to 3"
        else
        set foldcolumn=0
            echo "foldcolumn set to 0"
    endif
endfunction

" ftplugin
" .vim/after/ftplugin/markdown/folding.vim
"#====================================================================>