handle Android app events in frontend/device code

Events have been passed to the frontend/device (or /input) code before.
Some of them have been handled in the FFI/input code, however. That
seems to be highly critical with regard to timing, though, so we just
let it enqueue the event for our code to process later. That way, a
mutex that locks the input event queue can be freed faster.

frontend/device/android/device.lua

@@ -1,6 +1,7 @@
 local Generic = require("device/generic/device")
 local isAndroid, android = pcall(require, "android")
 local ffi = require("ffi")
+local DEBUG = require("dbg")
 
 local function yes() return true end
 
@@ -18,8 +19,13 @@ function Device:init()
         device = self,
         event_map = require("device/android/event_map"),
         handleMiscEv = function(self, ev)
+            DEBUG("Android application event", ev.code)
             if ev.code == ffi.C.APP_CMD_SAVE_STATE then
                 return "SaveState"
+            elseif ev.code == ffi.C.APP_CMD_GAINED_FOCUS then
+                self.device.screen:refreshFull()
+            elseif ev.code == ffi.C.APP_CMD_WINDOW_REDRAW_NEEDED then
+                self.device.screen:refreshFull()
             end
         end,
     }

frontend/device/input.lua

@@ -120,8 +120,6 @@ function Input:init()
         screen = self.device.screen,
         input = self,
     }
-    -- allow access to device object in FFI API
-    input.device = self.device
 
     -- set up fake event map
     self.event_map[10000] = "IntoSS" -- go into screen saver