[*] General code improvement.

* Rework navigation allowing direct management and triggering for grabkeyboard widgets.
* Navigation code now behaves better with deeply nested layouts.
* Allow widget hierarchies deeper than 2 (__call() is implemented for every Widget metatable).
* Make BASE locals more secure (match '<filename>$' in regexp)

input.lua

@@ -1,12 +1,15 @@
-local BASE = (...):gsub('input', '')
+local BASE = (...):gsub('input$', '')
 
 local Widget = require(BASE..'widget')
 local core = require(BASE..'core')
 
 local utf8 = require 'utf8'
 
--- Grabs keyboard on focus
-local Input = setmetatable({ grabkeyboard = true }, Widget)
+-- NOTE: Input manages keyboard directly.
+local Input = setmetatable({
+    grabkeyboard = true,
+    __call = function(cls, args) return cls.new(args) end
+}, Widget)
 Input.__index = Input
 
 
@@ -28,6 +31,18 @@ function Input.new(args)
     return self
 end
 
+-- NOTE: Input steals keyboard input on focus.
+function Input:gainFocus()
+    love.keyboard.setTextInput(true, self.x,self.y,self.w,self.h)
+    love.keyboard.setKeyRepeat(true)
+end
+function Input:loseFocus()
+    if love.system.getOS() == 'Android' or love.system.getOS() == 'iOS' then
+        love.keyboard.setTextInput(false)
+    end
+    love.keyboard.setKeyRepeat(false)
+end
+
 function Input:onPointerInput(px,py, clicked)
     if clicked then
         self:grabFocus()
@@ -92,9 +107,12 @@ function Input:keyreleased(key)
             self.cursor = 1
         elseif key == 'end' then
             self.cursor = utf8.len(self.text)+1
-        elseif key == 'return' then
-            self:onChange(self.text)
-            self.cursor = 1
+        elseif key == 'up' or key == 'down' then
+            self.ui:navigate(key)
+        elseif key == 'tab' or key == 'return' then
+            self.ui:navigate('right')
+        elseif key == 'escape' then
+            self.ui:navigate('cancel')
         end
     end
 end