[Android] misc fixes (#4478)

* use product as device model
* print android version (codename + number) + api at launch
* exit the application properly
* fix fullscreen switching (and disable it on newer android versions)
* gettext: lower log level for message: cannot open translation file
* android common settings refactor

frontend/ui/elements/screen_android.lua

@@ -0,0 +1,52 @@
+local isAndroid, android = pcall(require, "android")
+local Device = require("device")
+local Geom = require("ui/geometry")
+local logger = require("logger")
+local Input = Device.input
+local Screen = Device.screen
+
+if not isAndroid then return end
+
+local ScreenHelper = {}
+
+-- toggle android status bar visibility
+function ScreenHelper:toggleFullscreen()
+    -- toggle android status bar visibility
+    local is_fullscreen = android.isFullscreen()
+    android.setFullscreen(not is_fullscreen)
+    logger.dbg(string.format("requesting fullscreen: %s", not is_fullscreen))
+
+    local screen_width = android.getScreenWidth()
+    local screen_height = android.getScreenHeight()
+    local status_bar_height = android.getStatusBarHeight()
+    local new_height = screen_height - status_bar_height
+
+    if not is_fullscreen and Screen.viewport then
+        status_bar_height = 0
+        -- reset touchTranslate to normal
+        Input:registerEventAdjustHook(
+            Input.adjustTouchTranslate,
+            {x = 0 + Screen.viewport.x, y = 0 + Screen.viewport.y})
+    end
+
+    local viewport = Geom:new{x=0, y=status_bar_height, w=screen_width, h=new_height}
+    logger.info(string.format("Switching viewport to new geometry [x=%d,y=%d,w=%d,h=%d]",
+        0, status_bar_height, screen_width, new_height))
+
+    Screen:setViewport(viewport)
+
+    if is_fullscreen and Screen.viewport then
+        Input:registerEventAdjustHook(
+            Input.adjustTouchTranslate,
+            {x = 0 - Screen.viewport.x, y = 0 - Screen.viewport.y})
+    end
+end
+
+-- toggle android wakelock support
+function ScreenHelper:toggleWakelock()
+    local is_wakelock = not G_reader_settings:isTrue("disable_android_wakelock")
+    android.setWakeLock(not is_wakelock)
+    G_reader_settings:saveSetting("disable_android_wakelock", is_wakelock)
+end
+
+return ScreenHelper