-- TIME_STAMP   2022-03-17 10:43:14   v 0.1


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--[[
in...:  _line       A line of text whose TAB are to be replaced by spaces.
.....:  _tabsize    TAB size in number of characters. If it is omitted, 4 is used.
out..:  The line, with TAB replaced if necessary, and the number of replacements.
]]
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TabReplace_Line = function(_line, _tabsize)
    if _line:find('^[\r\n]+$') then return _line, 0 end -- only a line break
    if _line == '' then return _line, 0 end             -- only a empty string
    local posTab = _line:find('\t')
    if posTab == nil then return _line, 0 end           -- no TAB included
    _tabsize = _tabsize or 4                            -- default TAB width
    local tTab, s, sRep, iLen, sumLen = {}, ' ', '', 0, 0
    while posTab ~= nil do
        -- calculation replacement string, taking into account characters to be inserted
        iLen = (_tabsize - ((posTab + sumLen -1) % _tabsize))
        sumLen = sumLen + iLen -1                       -- total length of the replacements
        sRep = s:rep(iLen)                              -- create replacement string
        table.insert(tTab, sRep)                        -- save to table
        posTab = _line:find('\t', posTab +1)            -- find next TAB
    end
    local idx = 0
    _line = _line:gsub('\t', function() idx = idx +1 return tTab[idx] end)
    return _line, idx
end
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--[[
    Replaces all TAB in the file currently open in SciTE
]]
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TabReplace_FileInSciTE = function(_tabsize)
    local caret = editor.CurrentPos
    local fvl = editor.FirstVisibleLine
    local content = ''
    for i=0, editor.LineCount -1 do
        local line = editor:GetLine(i)
        line = TabReplace_Line(line, _tabsize)
        content = content..line
    end
    editor:BeginUndoAction()
    editor:ClearAll()
    editor:InsertText(0, content)
    editor:EndUndoAction()
    editor.CurrentPos = caret
    editor:SetSel(caret, caret)
    editor.FirstVisibleLine = fvl
end
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TabReplace_FileInSciTE(4)   -- If required: Change the TAB size here