use xpointer instead of read percent to mark read progress

frontend/ui/reader/readerrolling.lua

@@ -94,10 +94,21 @@ function ReaderRolling:onReadSettings(config)
 	if not soe then
 		self.show_overlap_enable = soe
 	end
-	self:gotoPercent(config:readSetting("last_percent") or 0)
-	-- we have to do a real pos change in self.ui.document._document to
-	-- update status information in CREngine.
-	self.ui.document:gotoPos(self.current_pos)
+	-- we read last_percent just for backward compatibility
+	local last_per = config:readSetting("last_percent")
+	if last_per then
+		self:gotoPercent(last_per)
+		-- we have to do a real pos change in self.ui.document._document to
+		-- update status information in CREngine.
+		self.ui.document:gotoPos(self.current_pos)
+	end
+	local last_xp = config:readSetting("last_xpointer")
+	if last_xp then
+		self:gotoXPointer(last_xp)
+		-- we have to do a real jump in self.ui.document._document to
+		-- update status information in CREngine.
+		self.ui.document:gotoXPointer(last_xp)
+	end
 	if self.view_mode == "page" then
 		self.ui:handleEvent(Event:new("PageUpdate", self.ui.document:getCurrentPage()))
 	end
@@ -106,7 +117,9 @@ end
 function ReaderRolling:onCloseDocument()
 	local cur_xp = self.ui.document:getXPointer()
 	local cur_pos = self.ui.document:getPosFromXPointer(cur_xp)
-	self.ui.doc_settings:saveSetting("last_percent", 10000 * cur_pos / self.doc_height)
+	-- remove last_percent config since its deprecated
+	self.ui.doc_settings:saveSetting("last_percent", nil)
+	self.ui.doc_settings:saveSetting("last_xpointer", self.ui.document:getXPointer())
 	self.ui.doc_settings:saveSetting("percent_finished", cur_pos / self.doc_height)
 end