refactoring restoreScreenMode from readerview to filemanager

This should fix #983.

frontend/apps/filemanager/filemanager.lua

@@ -173,10 +173,13 @@ function FileManager:getDefaultDir()
     end
 end
 
+function FileManager:restoreScreenMode()
+    local screen_mode = G_reader_settings:readSetting("fm_screen_mode")
+    Screen:setScreenMode(screen_mode or "portrait")
+end
+
 function FileManager:showFiles(path)
     DEBUG("show home page")
-    local screen_mode = G_reader_settings:readSetting("fm_screen_mode") or "portrait"
-    Screen:setScreenMode(screen_mode)
     path = path or G_reader_settings:readSetting("lastdir") or self:getDefaultDir()
     G_reader_settings:saveSetting("lastdir", path)
     UIManager:show(FileManager:new{

frontend/apps/reader/modules/readermenu.lua

@@ -43,7 +43,10 @@ function ReaderMenu:init()
             callback = function()
                 self.ui:onClose()
                 self:onTapCloseMenu()
+                -- screen orientation is independent for docview and filemanager
+                -- so we need to restore the screen mode for the filemanager
                 local FileManager = require("apps/filemanager/filemanager")
+                FileManager:restoreScreenMode()
                 if not FileManager.is_running then
                     UIManager:quit()
                     FileManager:showFiles()

frontend/apps/reader/modules/readerview.lua

@@ -545,15 +545,6 @@ function ReaderView:onSetScreenMode(new_mode, rotation)
     return true
 end
 
--- for returning to FileManager
-function ReaderView:onRestoreScreenMode(old_mode)
-    if old_mode == "landscape" or old_mode == "portrait" then
-        Screen:setScreenMode(old_mode)
-        self.ui:handleEvent(Event:new("SetDimensions", Screen:getSize()))
-    end
-    return true
-end
-
 function ReaderView:onSetDimensions(dimensions)
     self:resetLayout()
     self.dimen = dimensions