[*] 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)

ui.lua

@@ -2,6 +2,8 @@ local BASE = (...):gsub('ui$', '')
 
 local Widget = require(BASE..'widget')
 local Layout = require(BASE..'layout')
+local Columns = require(BASE..'columns')
+local Rows = require(BASE..'rows')
 
 local gear = require 'lib.gear'
 
@@ -50,24 +52,6 @@ local function resolveautofocus(widget)
     return firstfocus, cancelfocus
 end
 
-local function propagateaction(ui, action)
-    local focused = ui.focused
-    if focused.grabkeyboard then
-        -- A widget stealing input
-        -- explicitly consumes any action.
-        return true
-    end
-    while focused ~= nil do
-        if focused:onActionInput(action) then
-            return true  -- action consumed
-        end
-
-        focused = focused.parent
-    end
-
-    return false
-end
-
 function Ui.new(args)
     local self = setmetatable(args, Ui)
     assert(#self == 1, "Ui.new() must have exactly one root widget.")
@@ -98,7 +82,7 @@ function Ui.new(args)
     local firstfocus, cancelfocus = resolveautofocus(root)
     if firstfocus == nil then
         firstfocus = isinstance(root, Layout) and
-                     root:firstFocusableWidget() or
+                     root:first() or
                      root
     end
 
@@ -138,28 +122,136 @@ function Ui:textedited(text, start, length)
     end
 end
 
-function Ui:update(dt)
-    local root = self[1]
-    local x,y,w,h = root.x,root.y,root.w,root.h
-    local snap = self.device:snapshot()
+local function actionpropagate(widget, action)
+    while widget ~= nil do
+        if widget:onActionInput(action) then
+            return true  -- action consumed
+        end
 
-    self.timer:update(dt)
+        widget = widget.parent
+    end
+
+    return false
+end
+
+local navs = { 'cancel', 'up', 'down', 'left', 'right' }
+
+local function globalactions(ui, snap)
+    for _,nav in ipairs(navs) do
+        if snap[nav] then
+            ui:navigate(nav)
+            break  -- discard other directions, if any
+        end
+    end
+end
+
+local function eventpropagate(ui, snap)
+    -- 1. Pointer events
+    if snap.pointer and not ui.grabpointer then
+        local root = ui[1]
+        local x,y,w,h = root.x,root.y,root.w,root.h
 
-    -- Propagate pointer events in focus order
-    if self.pointerActive then
         if snap.pointer and pointinrect(snap.px,snap.py, x,y,w,h) then
             root:onPointerInput(snap.px,snap.py, snap.clicked, snap.pointing)
         end
     end
 
-    -- Propagate actions from focused widget up
-    if snap.action and not propagateaction(self, snap) then
-        -- Take global actions if nobody consumed the event
-        if snap.cancel and self.cancelfocus then
-            -- Focus on the last widget with 'cancelfocus'
-            self.cancelfocus:grabFocus()
+    -- 2. Actions (keyboard/buttons)
+    if snap.action and not ui.grabkeyboard then
+        local consumed = actionpropagate(ui.focused, snap)
+
+        if not consumed then
+            -- 3. If no widget consumed action,
+            --    take global actions (e.g. navigation).
+            globalactions(ui, snap)
         end
     end
+end
+
+-- cls may be Rows, Columns or Layout in general
+local function containerof(widget, cls)
+    repeat
+        widget = widget.parent
+        if isinstance(widget, cls) then
+            return widget
+        end
+    until widget == nil
+end
+
+local function findprev(ui, cls, widget)
+    local child = widget
+
+    while true do
+        local container = containerof(child, cls)
+        if container == nil then
+            -- All the way up, either return the original
+            -- widget or wraparound to the bottom
+            return isinstance(child, cls) and child:last() or widget
+        end
+
+        local w = container:before(child)
+        if w ~= nil then
+            return w
+        end
+
+        child = container  -- move up into the hierarchy
+    end
+end
+
+-- Specular to findprev()
+local function findnext(ui, cls, widget)
+    local child = widget
+
+    while true do
+        local container = containerof(child, cls)
+        if container == nil then
+            return isinstance(child, cls) and child:first() or widget
+        end
+
+        local w = container:after(child)
+        if w ~= nil then
+            return w
+        end
+
+        child = container
+    end
+end
+
+--- Move focus to the given direction.
+--
+-- @param where (string) Direction to move to,
+--                       one of: 'up', 'down', 'left', 'right', 'cancel'.
+function Ui:navigate(where)
+    local nextfocus = nil
+
+    if where == 'cancel' then
+        nextfocus = self.cancelfocus
+    elseif where == 'up' then
+        nextfocus = findprev(self, Rows, self.focused)
+    elseif where == 'down' then
+        nextfocus = findnext(self, Rows, self.focused)
+    elseif where == 'left' then
+        nextfocus = findprev(self, Columns, self.focused)
+    elseif where == 'right' then
+        nextfocus = findnext(self, Columns, self.focused)
+    else
+        error("Bad direction: "..tostring(where))
+    end
+
+    if nextfocus ~= nil then
+        nextfocus:grabFocus()
+    end
+end
+
+function Ui:update(dt)
+    local root = self[1]
+    local snap = self.device:snapshot()
+
+    -- Update timer related effects
+    self.timer:update(dt)
+
+    -- Regular event propagation
+    eventpropagate(self, snap)
 
     -- Perform regular lifetime updates
     root:update(dt)