[*] 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)

layout.lua

@@ -1,4 +1,4 @@
-local BASE = (...):gsub('layout', '')
+local BASE = (...):gsub('layout$', '')
 
 local Widget = require(BASE..'widget')
 local core = require(BASE..'core')
@@ -9,7 +9,9 @@ local isinstance = gear.meta.isinstance
 local rectunion = gear.rect.union
 local pointinrect = gear.rect.pointinside
 
-local Layout = setmetatable({}, Widget)
+local Layout = setmetatable({
+    __call = function(cls, args) return cls.new(args) end
+}, Widget)
 Layout.__index = Layout
 
 
@@ -113,21 +115,6 @@ function Layout:layoutWidgets()
     self.h = math.max(rh, 0)
 end
 
-function Layout:onPointerInput(px,py, clicked, down)
-    local stack = self.stack
-
-    -- Propagate pointer event from topmost widget to bottom
-    for i = #stack,1,-1 do
-        local widget = stack[i]
-        local x,y,w,h = widget.x,widget.y,widget.w,widget.h
-
-        if pointinrect(px,py, x,y,w,h) then
-            widget:onPointerInput(px,py, clicked, down)
-            break
-        end
-    end
-end
-
 -- Find layout's child containing the provided widget.
 local function childof(layout, widget)
     local parent = widget.parent
@@ -137,98 +124,27 @@ local function childof(layout, widget)
     end
     return widget
 end
-local function findfirst(widget)
-    while isinstance(widget, Layout) do
-        -- Find first element accepting focus
-        for i = 1,#widget do
-            if not widget[i].nofocus then
-                widget = widget[i]
-                break
-            end
+local function scanforward(layout, from)
+    from = from or 1
+
+    for i = from,#layout do
+        local w = layout[i]
+
+        if not w.nofocus then
+            return isinstance(w, Layout) and scanforward(w) or w
         end
     end
-    return widget
 end
-local function findnext(layout, widget)
-    local child = childof(layout, widget)
+local function scanbackwards(layout, from)
+    from = from or #layout
 
-    for i,w in ipairs(layout) do
-        if w == child then
-            -- Search to the right, wraparound to the left
-            for j = i+1,#layout do
-                if not layout[j].nofocus then
-                    return findfirst(layout[j])
-                end
-            end
-            for j = 1,i-1 do
-                if not layout[j].nofocus then
-                    return findfirst(layout[j])
-                end
-            end
+    for i = from,1,-1 do
+        local w = layout[i]
+
+        if not w.nofocus then
+            return isinstance(w, Layout) and scanforward(w) or w
         end
     end
-    return widget
-end
-local function findprev(layout, widget)
-    local child = childof(layout, widget)
-
-    for i,w in ipairs(layout) do
-        if w == child then
-            -- Search to the left, wraparound to the right
-            for j = i-1,1,-1 do
-                if not layout[j].nofocus then
-                    return findfirst(layout[j])
-                end
-            end
-            for j = #layout,i+1,-1 do
-                if not layout[j].nofocus then
-                    return findfirst(layout[j])
-                end
-            end
-        end
-    end
-    return widget
-end
-
-function Layout:firstFocusableWidget()
-    return findfirst(self)
-end
-function Layout:nextFocusableWidget()
-    return findnext(self, self.ui.focused)
-end
-function Layout:previousFocusableWidget()
-    return findprev(self, self.ui.focused)
-end
-
-function Layout:onActionInput(action)
-    local handled = false
-
-    if action[self.next] then
-        local n = self:nextFocusableWidget()
-
-        n:grabFocus()
-        handled = true
-    end
-    if action[self.prev] then
-        local p = self:previousFocusableWidget()
-
-        p:grabFocus()
-        handled = true
-    end
-    return handled
-end
-
-function Layout:update(dt)
-    for _,widget in ipairs(self.stack) do
-        widget:update(dt)
-    end
-end
-
-function Layout:draw()
-    -- Draw all children according to their order (topmost last)
-    for _,widget in ipairs(self.stack) do
-        widget:draw()
-    end
 end
 
 function Layout.new(args)
@@ -245,7 +161,70 @@ function Layout.new(args)
             break
         end
     end
+
     return self
 end
 
+--- Find first widget in layout accepting focus.
+function Layout:first()
+    return scanforward(self)
+end
+
+--- Find last widget in layout accepting focus.
+function Layout:last()
+    return scanbackwards(self)
+end
+
+--- Find next focusable widget after the provided one.
+function Layout:after(widget)
+    widget = childof(self, widget)
+
+    for i = 1,#self do
+        if self[i] == widget then
+            -- Search to the right/down
+            return scanforward(self, i+1)
+        end
+    end
+end
+
+--- Find previous focusable widget before the provided one.
+function Layout:before(widget)
+    widget = childof(self, widget)
+
+    for i = 1,#self do
+        if self[i] == widget then
+            -- Search to the left/up
+            return scanbackwards(self, i-1)
+        end
+    end
+end
+
+function Layout:onPointerInput(px,py, clicked, down)
+    local stack = self.stack
+
+    -- Propagate pointer event from topmost widget to bottom
+    for i = #stack,1,-1 do
+        local widget = stack[i]
+        local x,y,w,h = widget.x,widget.y,widget.w,widget.h
+
+        if pointinrect(px,py, x,y,w,h) then
+            widget:onPointerInput(px,py, clicked, down)
+            break
+        end
+    end
+end
+
+function Layout:update(dt)
+    for _,widget in ipairs(self.stack) do
+        widget:update(dt)
+    end
+end
+
+function Layout:draw()
+    -- Draw all children according to their order (topmost last)
+    for _,widget in ipairs(self.stack) do
+        widget:draw()
+    end
+end
+
 return Layout