Implement numeric collator (natural sorting) in file manager (#6378)

frontend/apps/filemanager/filemanager.lua

@@ -951,6 +951,7 @@ function FileManager:getSortingMenuTable()
     local fm = self
     local collates = {
         strcoll = {_("filename"), _("Sort by filename")},
+        numeric = {_("numeric"), _("Sort by filename (natural sorting)")},
         strcoll_mixed = {_("name mixed"), _("Sort by name – mixed files and folders")},
         access = {_("date read"), _("Sort by last read date")},
         change = {_("date added"), _("Sort by date added")},
@@ -992,6 +993,7 @@ function FileManager:getSortingMenuTable()
             set_collate_table("modification"),
             set_collate_table("size"),
             set_collate_table("type"),
+            set_collate_table("numeric"),
             {
                 text_func =  get_collate_percent,
                 checked_func = function()

frontend/ui/widget/filechooser.lua

@@ -193,6 +193,16 @@ function FileChooser:genItemTableFromPath(path)
 
             return a.percent_finished < b.percent_finished
         end
+    elseif self.collate == "numeric" then
+        -- adapted from: http://notebook.kulchenko.com/algorithms/alphanumeric-natural-sorting-for-humans-in-lua
+        local function addLeadingZeroes(d)
+            local dec, n = string.match(d, "(%.?)0*(.+)")
+            return #dec > 0 and ("%.12f"):format(d) or ("%s%03d%s"):format(dec, #n, n)
+        end
+        sorting = function(a, b)
+            return tostring(a.name):gsub("%.?%d+", addLeadingZeroes)..("%3d"):format(#b.name)
+                    < tostring(b.name):gsub("%.?%d+",addLeadingZeroes)..("%3d"):format(#a.name)
+        end
     else
         sorting = function(a, b)
             return a.name < b.name