AutoSuspend: Unbreak scheduling & settings across instances

Plugins are loaded *once*, but torn-down/instantiated multiple times,
and sometimes in the reverse order.

As such, if we use a public function member as the scheduled task, we're
always pointing to the same function, and going from FM to RD
effectively *un*schedules it.

Instead, use an instance-specific closure, so that each instance
schedules & unschedules don't affect each other.

In the same vein, settings ought to be read at instantiation, not at
loading, otherwise, changing a setting in the FM, then switching to the
reader will not pick up the changes.

plugins/autosuspend.koplugin/main.lua

@@ -24,10 +24,11 @@ local default_auto_suspend_timeout_seconds = 60*60
 local AutoSuspend = WidgetContainer:new{
     name = "autosuspend",
     is_doc_only = false,
-    autoshutdown_timeout_seconds = G_reader_settings:readSetting("autoshutdown_timeout_seconds") or default_autoshutdown_timeout_seconds,
-    auto_suspend_timeout_seconds = G_reader_settings:readSetting("auto_suspend_timeout_seconds") or default_auto_suspend_timeout_seconds,
-    last_action_tv = TimeVal:now(),
+    autoshutdown_timeout_seconds = default_autoshutdown_timeout_seconds,
+    auto_suspend_timeout_seconds = default_auto_suspend_timeout_seconds,
+    last_action_tv = TimeVal.zero,
     standby_prevented = false,
+    task = nil,
 }
 
 function AutoSuspend:_enabled()
@@ -67,18 +68,20 @@ function AutoSuspend:_schedule(shutdown_only)
     else
         if self:_enabled() and not shutdown_only then
             logger.dbg("AutoSuspend: scheduling next suspend check in", delay_suspend)
-            UIManager:scheduleIn(delay_suspend, self._schedule, self, shutdown_only)
+            UIManager:scheduleIn(delay_suspend, self.task)
         end
         if self:_enabledShutdown() then
             logger.dbg("AutoSuspend: scheduling next shutdown check in", delay_shutdown)
-            UIManager:scheduleIn(delay_shutdown, self._schedule, self, shutdown_only)
+            UIManager:scheduleIn(delay_shutdown, self.task)
         end
     end
 end
 
 function AutoSuspend:_unschedule()
-    logger.dbg("AutoSuspend: unschedule")
-    UIManager:unschedule(self._schedule)
+    if self.task then
+        logger.dbg("AutoSuspend: unschedule")
+        UIManager:unschedule(self.task)
+    end
 end
 
 function AutoSuspend:_start()
@@ -103,8 +106,15 @@ end
 function AutoSuspend:init()
     logger.dbg("AutoSuspend: init")
     if Device:isPocketBook() and not Device:canSuspend() then return end
+    self.autoshutdown_timeout_seconds = G_reader_settings:readSetting("autoshutdown_timeout_seconds") or default_autoshutdown_timeout_seconds
+    self.auto_suspend_timeout_seconds = G_reader_settings:readSetting("auto_suspend_timeout_seconds") or default_auto_suspend_timeout_seconds
+
     UIManager.event_hook:registerWidget("InputEvent", self)
-    self:_unschedule()
+    -- We need an instance-specific function reference to schedule, because when going from FM to RD,
+    -- we instantiate the RD instance *before* tearing down the old FM instance.
+    self.task = function(shutdown_only)
+        self:_schedule(shutdown_only)
+    end
     self:_start()
     -- self.ui is nil in the testsuite
     if not self.ui or not self.ui.menu then return end
@@ -116,6 +126,7 @@ function AutoSuspend:onCloseWidget()
     logger.dbg("AutoSuspend: onCloseWidget")
     if Device:isPocketBook() and not Device:canSuspend() then return end
     self:_unschedule()
+    self.task = nil
 end
 
 function AutoSuspend:onInputEvent()