no need to do full screen refresh when outof screensaver

since there is already one by the native system

frontend/device/emulator/device.lua

@@ -3,6 +3,7 @@ local util = require("ffi/util")
 local DEBUG = require("dbg")
 
 local function yes() return true end
+local function no() return false end
 
 local Device = Generic:new{
     model = "Emulator",
@@ -12,6 +13,7 @@ local Device = Generic:new{
     hasDPad = yes,
     hasFrontlight = yes,
     isTouchDevice = yes,
+    needsScreenRefreshAfterResume = no,
 }
 
 function Device:init()

frontend/device/generic/device.lua

@@ -2,6 +2,7 @@ local Event = require("ui/event")
 local util = require("ffi/util")
 local DEBUG = require("dbg")
 
+local function yes() return true end
 local function no() return false end
 
 local Device = {
@@ -34,6 +35,8 @@ local Device = {
     viewport = nil,
     -- enforce portrait orientation on display, no matter how configured at startup
     isAlwaysPortrait = no,
+    -- needs full screen refresh when resumed from screensaver?
+    needsScreenRefreshAfterResume = yes,
 }
 
 function Device:new(o)
@@ -132,7 +135,9 @@ end
 function Device:resume()
     local UIManager = require("ui/uimanager")
     UIManager:unschedule(self.suspend)
-    self.screen:refreshFull()
+    if self:needsScreenRefreshAfterResume() then
+        self.screen:refreshFull()
+    end
     self.screen_saver_mode = false
     self.powerd:refreshCapacity()
 end

frontend/device/kindle/device.lua

@@ -2,6 +2,7 @@ local Generic = require("device/generic/device")
 local DEBUG = require("dbg")
 
 local function yes() return true end
+local function no() return false end
 
 local Kindle = Generic:new{
     model = "Kindle",
@@ -71,6 +72,7 @@ local KindleVoyage = Kindle:new{
     hasKeys = yes,
     display_dpi = 300,
     touch_dev = "/dev/input/event1",
+    needsScreenRefreshAfterResume = no,
 }
 
 local KindlePaperWhite3 = Kindle:new{