[feat, Kobo] Implement shutdown from suspend (#5280)

This allows to shutdown straight from suspend just like Nickel.

Fixes <https://github.com/koreader/koreader/issues/2431>.

frontend/device/input.lua

@@ -343,16 +343,10 @@ function Input:handleKeyBoardEv(ev)
     if keycode == "Power" then
         -- Kobo generates Power keycode only, we need to decide whether it's
         -- power-on or power-off ourselves.
-        if self.device.screen_saver_mode then
-            if ev.value == EVENT_VALUE_KEY_RELEASE then
-                return "Resume"
-            end
-        else
-            if ev.value == EVENT_VALUE_KEY_PRESS then
-                return "PowerPress"
-            elseif ev.value == EVENT_VALUE_KEY_RELEASE then
-                return "PowerRelease"
-            end
+        if ev.value == EVENT_VALUE_KEY_PRESS then
+            return "PowerPress"
+        elseif ev.value == EVENT_VALUE_KEY_RELEASE then
+            return "PowerRelease"
         end
     end
 

frontend/ui/uimanager.lua

@@ -109,12 +109,19 @@ function UIManager:init()
             end
         end
         self.event_handlers["PowerPress"] = function()
+            -- Always schedule power off.
+            -- Press the power button for 2+ seconds to shutdown directly from suspend.
             UIManager:scheduleIn(2, self.poweroff_action)
         end
         self.event_handlers["PowerRelease"] = function()
             if not self._entered_poweroff_stage then
                 UIManager:unschedule(self.poweroff_action)
-                self:suspend()
+                -- resume if we were suspended
+                if Device.screen_saver_mode then
+                    self:resume()
+                else
+                    self:suspend()
+                end
             end
         end
         -- Sleep Cover handling