small change of UIManager:show(): No more automatic refresh

This eliminates the API difference between the extra parameters of
UIManager:show() and setDirty(). They work the same now.
Note that this also eliminates the automatic refresh that took place
before when using show() without refresh options. It always refreshed
the full screen, which led to too big refresh regions all over the
place. Thus, refresh has now explicitly to be asked for, hopefully
encouraging to implement it in the widget that gets shown (and is
aware about the screen region it covers).

Also add an event that is triggered when a widget is closed:
CloseWidget. So a widget can implement "onCloseWidget()" to trigger
actions upon closing - most commonly, this is a refresh for the area
previously taken by the widget. That way, the widget's user does not
have to take measures to ensure that the area is refreshed later.

frontend/ui/uimanager.lua

@@ -84,7 +84,7 @@ end
 -- register & show a widget
 -- modal widget should be always on the top
 -- for refreshtype & refreshregion see description of setDirty()
-function UIManager:show(widget, x, y, refreshtype, refreshregion)
+function UIManager:show(widget, refreshtype, refreshregion, x, y)
     DEBUG("show widget", widget.id)
     self._running = true
     local window = {x = x or 0, y = y or 0, widget = widget}
@@ -98,7 +98,7 @@ function UIManager:show(widget, x, y, refreshtype, refreshregion)
         end
     end
     -- and schedule it to be painted
-    self:setDirty(widget, refreshtype or "partial", refreshregion)
+    self:setDirty(widget, refreshtype, refreshregion)
     -- tell the widget that it is shown now
     widget:handleEvent(Event:new("Show"))
     -- check if this widget disables double tap gesture
@@ -120,6 +120,8 @@ function UIManager:close(widget, refreshtype, refreshregion)
     local dirty = false
     for i = #self._window_stack, 1, -1 do
         if self._window_stack[i].widget == widget then
+            -- tell the widget that it is closed now
+            widget:handleEvent(Event:new("CloseWidget"))
             table.remove(self._window_stack, i)
             dirty = true
         elseif self._window_stack[i].widget.disable_double_tap then
@@ -207,7 +209,6 @@ function UIManager:setDirty(widget, refreshtype, refreshregion)
         end
     end
     -- handle refresh information
-    if not refreshtype or refreshtype == "none" then return end
     if type(refreshtype) == "function" then
         -- callback, will be issued after painting
         table.insert(self._refresh_func_stack, refreshtype)