add cursor functionality

frontend/util.lua

@@ -1,3 +1,5 @@
+local BaseUtil = require("ffi/util")
+
 --[[--
 Miscellaneous helper functions for KOReader frontend.
   ]]
@@ -94,4 +96,31 @@ function util.lastIndexOf(string, ch)
     if i == nil then return -1 else return i - 1 end
 end
 
+
+-- Split string into a list of UTF-8 chars.
+-- @text: the string to be splitted.
+-- @tab: the table to store the chars sequentially, must not be nil.
+function util.splitToChars(text, tab)
+	if text == nil then return end
+    -- clear
+    for k, v in pairs(tab) do
+		tab[k] = nil
+	end
+	print("table", tab)
+    local prevcharcode, charcode = 0
+    for uchar in string.gfind(text, "([%z\1-\127\194-\244][\128-\191]*)") do
+        charcode = BaseUtil.utf8charcode(uchar)
+        if prevcharcode then -- utf8
+            table.insert(tab, uchar)
+        end
+        prevcharcode = charcode
+    end
+	print(table.concat(tab, ","))
+end
+
+-- Test whether a string could be separated by a char for multi-line rendering
+function util.isSplitable(c)
+	return #c > 1 or c == " " or string.match(c, "%p") ~= nil
+end
+
 return util