resolve ANR on hold and native light dialog

frontend/device/android/device.lua

@@ -362,13 +362,41 @@ function Device:canExecuteScript(file)
     end
 end
 
+--swallow all events
+local function processEvents()
+    local events = ffi.new("int[1]")
+    local source = ffi.new("struct android_poll_source*[1]")
+    local poll_state = android.lib.ALooper_pollAll(-1, nil, events, ffi.cast("void**", source))
+    if poll_state >= 0 then
+        if source[0] ~= nil then
+            if source[0].id == C.LOOPER_ID_MAIN then
+                local cmd = C.android_app_read_cmd(android.app)
+                C.android_app_pre_exec_cmd(android.app, cmd)
+                C.android_app_post_exec_cmd(android.app, cmd)
+            elseif source[0].id == C.LOOPER_ID_INPUT then
+                local event = ffi.new("AInputEvent*[1]")
+                while android.lib.AInputQueue_getEvent(android.app.inputQueue, event) >= 0 do
+                    if android.lib.AInputQueue_preDispatchEvent(android.app.inputQueue, event[0]) == 0 then
+                        android.lib.AInputQueue_finishEvent(android.app.inputQueue, event[0], 1)
+                    end
+                end
+            end
+        end
+    end
+end
+
 function Device:showLightDialog()
     local usleep = require("ffi/util").usleep
     local title = android.isEink() and _("Frontlight settings") or _("Light settings")
     android.lights.showDialog(title, _("Brightness"), _("Warmth"), _("OK"), _("Cancel"))
     repeat
+        processEvents() -- swallow all events, including the last one
         usleep(25000) -- sleep 25ms before next check if dialog was quit
     until (android.lights.dialogState() ~= C.ALIGHTS_DIALOG_OPENED)
+
+    local GestureDetector = require("device/gesturedetector")
+    GestureDetector:clearStates()
+
     local action = android.lights.dialogState()
     if action == C.ALIGHTS_DIALOG_OK then
         self.powerd.fl_intensity = self.powerd:frontlightIntensityHW()