Just save settings that really were changed

And not also settings that are different from the ones loaded.
This prevents Koreader from overwriting your complete persistent.defaults.settings when you started Koreader with a malformated persistent.defaults.settings file and choose "save settings". In such a malformated case you just can edit the damaged setting and save it back (although you can't see which one is damaged since the defaults settings are taken)

frontend/apps/filemanager/filemanagersetdefaults.lua

@@ -14,7 +14,8 @@ local SetDefaults = InputContainer:new{
     defaults_value = {},
     results = {},
     defaults_menu = {},
-    already_read = false
+    already_read = false,
+    changed = {}
 }
 
 local function settype(b,t)
@@ -111,6 +112,7 @@ function SetDefaults:init()
     end
 
     for i=1,#self.defaults_name do
+        self.changed[i] = false
         local settings_type = type(_G[self.defaults_name[i]])
         if settings_type == "boolean" then
             table.insert(self.results, {
@@ -134,10 +136,9 @@ function SetDefaults:init()
                                     enabled = true,
                                     callback = function()
                                         self.defaults_value[i] = true
-                                        if not _G[self.defaults_name[i]] then
-                                            _G[self.defaults_name[i]] = true
-                                            settings_changed = true
-                                        end
+                                        _G[self.defaults_name[i]] = true
+                                        settings_changed = true
+                                        self.changed[i] = true
                                         self.results[i].text = self:build_setting(i)
                                         self:close()
                                         self.defaults_menu:swithItemTable("Defaults", self.results, i)
@@ -149,10 +150,9 @@ function SetDefaults:init()
                                     enabled = true,
                                     callback = function()
                                         self.defaults_value[i] = false
-                                        if _G[self.defaults_name[i]] then
-                                            _G[self.defaults_name[i]] = false
-                                            settings_changed = true
-                                        end
+                                        _G[self.defaults_name[i]] = false
+                                        settings_changed = true
+                                        self.changed[i] = true
                                         self.results[i].text = self:build_setting(i)
                                         self.defaults_menu:swithItemTable("Defaults", self.results, i)
                                         self:close()
@@ -192,14 +192,13 @@ function SetDefaults:init()
                                     enabled = true,
                                     callback = function()
                                         if type(_G[self.defaults_name[i]]) == "table" then
-                                            settings_changed = true
                                             self.defaults_value[i] = self.set_dialog:getInputText()
                                         elseif _G[self.defaults_name[i]] ~= settype(self.set_dialog:getInputText(),settings_type) then
                                             _G[self.defaults_name[i]] = settype(self.set_dialog:getInputText(),settings_type)
-                                            settings_changed = true
                                             self.defaults_value[i] = _G[self.defaults_name[i]]
                                         end
-                                        
+                                        settings_changed = true
+                                        self.changed[i] = true
                                         self.results[i].text = self:build_setting(i)
                                         self:close()
                                         self.defaults_menu:swithItemTable("Defaults", self.results, i)
@@ -315,10 +314,14 @@ function SetDefaults:SaveSettings()
     self.filldefaults()
     local done = {}
 
+    for j=1,#SetDefaults.defaults_name do
+        if not self.changed[j] then done[j] = true end
+    end
+
     -- handle case "found in persistent", replace it
     for i = 1,#dpl do
         for j=1,#SetDefaults.defaults_name do
-            if string.find(dpl[i],SetDefaults.defaults_name[j] .. " ") == 1 then
+            if not done[j] and string.find(dpl[i],SetDefaults.defaults_name[j] .. " ") == 1 then
                 dpl[i] = self:build_setting(j)
                 done[j] = true
             end
@@ -328,7 +331,7 @@ function SetDefaults:SaveSettings()
     -- handle case "exists identical in non-persistent", ignore it
     for i = 1,#dl do
         for j=1,#SetDefaults.defaults_name do
-            if dl[i]:gsub("1/4","0.25"):gsub("2/4","0.5"):gsub("3/4","0.75"):gsub("4/4","1"):gsub("1/8","0.125"):gsub("2/8","0.25"):gsub("3/8","0.375"):gsub("4/8","0.5"):gsub("5/8","0.625"):gsub("6/8","0.75"):gsub("7/8","0.875"):gsub("8/8","1"):gsub("1/16","0.0625"):gsub("15/16","0.9375"):gsub("1024[*]1024[*]10","10485760"):gsub("1024[*]1024[*]30","31457280"):gsub("[.]0$",""):gsub("([.][0-9]+)0","%1") == self:build_setting(j) then
+            if not done[j] and dl[i]:gsub("1/4","0.25"):gsub("2/4","0.5"):gsub("3/4","0.75"):gsub("4/4","1"):gsub("1/8","0.125"):gsub("2/8","0.25"):gsub("3/8","0.375"):gsub("4/8","0.5"):gsub("5/8","0.625"):gsub("6/8","0.75"):gsub("7/8","0.875"):gsub("8/8","1"):gsub("1/16","0.0625"):gsub("15/16","0.9375"):gsub("1024[*]1024[*]10","10485760"):gsub("1024[*]1024[*]30","31457280"):gsub("[.]0$",""):gsub("([.][0-9]+)0","%1") == self:build_setting(j) then
                 done[j] = true
             end
         end