Add focus/UI modes and clean up event generation.

UI controls occasionally trap focus and make navigation impossible. Now, Ctrl+escape toggles a mode that attempts to intercept and generate UI focus events and bypass the control's own handling. This can probably be refined, but for now it allows escaping of `TextEdit` via tab. It also won't work everywhere--inn particular, arrowing around still traps focus in trees. But it is at least possible to tab out of most traps.

Further, event generation was cleaned up some. We specifically need to generate `KeyEvents` under Android because, IIRC, it wasn't enough to simply create and send some types of events. We now have two distinct generation strategies. These can probably be combined and streamlined, but for now this works.

ScreenReader.gd

@@ -19,6 +19,8 @@ export var tap_execute_interval = 125
 
 export var explore_by_touch_interval = 200
 
+export var enable_focus_mode = false
+
 var focus_restore_timer
 
 
@@ -117,7 +119,7 @@ func _enter_tree():
 	connect("swipe_down", self, "swipe_down")
 
 
-func press_and_release(action):
+func _press_and_release(action):
 	var event = InputEventAction.new()
 	event.action = action
 	event.pressed = true
@@ -126,28 +128,40 @@ func press_and_release(action):
 	get_tree().input_event(event)
 
 
-func _ui_focus_next():
-	for event in InputMap.get_action_list("ui_focus_next"):
+func _send_via_keyboard(action):
+	for event in InputMap.get_action_list(action):
 		if event is InputEventKey:
 			event.pressed = true
-			Input.action_press("ui_focus_next")
+			Input.action_press(action)
 			get_tree().input_event(event)
 			event.pressed = false
-			Input.action_release("ui_focus_next")
+			Input.action_release(action)
 			get_tree().input_event(event)
 			return
 
 
+func _ui_left():
+	_send_via_keyboard("ui_left")
+
+
+func _ui_right():
+	_send_via_keyboard("ui_right")
+
+
+func _ui_up():
+	_send_via_keyboard("ui_up")
+
+
+func _ui_down():
+	_send_via_keyboard("ui_down")
+
+
+func _ui_focus_next():
+	_send_via_keyboard("ui_focus_next")
+
+
 func _ui_focus_prev():
-	for event in InputMap.get_action_list("ui_focus_prev"):
-		if event is InputEventKey:
-			event.pressed = true
-			Input.action_press("ui_focus_prev")
-			get_tree().input_event(event)
-			event.pressed = false
-			Input.action_release("ui_focus_prev")
-			get_tree().input_event(event)
-			return
+	_send_via_keyboard("ui_focus_prev")
 
 
 func swipe_right():
@@ -178,10 +192,56 @@ var explore_by_touch = false
 
 var tap_count = 0
 
+var focus_mode = false
+var in_focus_mode_handler = false
+
 
 func _input(event):
 	if not enabled:
 		return
+	if enable_focus_mode:
+		if (
+			event is InputEventKey
+			and Input.is_key_pressed(KEY_ESCAPE)
+			and Input.is_key_pressed(KEY_CONTROL)
+			and not event.echo
+		):
+			get_tree().set_input_as_handled()
+			if focus_mode:
+				focus_mode = false
+				TTS.speak("UI mode", true)
+				return
+			else:
+				focus_mode = true
+				TTS.speak("Focus mode", true)
+				return
+		if focus_mode:
+			if (
+				Input.is_action_just_pressed("ui_left")
+				or Input.is_action_just_pressed("ui_right")
+				or Input.is_action_just_pressed("ui_up")
+				or Input.is_action_just_pressed("ui_down")
+				or Input.is_action_just_pressed("ui_focus_next")
+				or Input.is_action_just_pressed("ui_focus_prev")
+			):
+				if in_focus_mode_handler:
+					return
+				in_focus_mode_handler = true
+				if Input.is_action_just_pressed("ui_left"):
+					_ui_left()
+				elif Input.is_action_just_pressed("ui_right"):
+					_ui_right()
+				elif Input.is_action_just_pressed("ui_up"):
+					_ui_up()
+				elif Input.is_action_just_pressed("ui_down"):
+					_ui_down()
+				elif Input.is_action_just_pressed("ui_focus_prev"):
+					_ui_focus_prev()
+				elif Input.is_action_just_pressed("ui_focus_next"):
+					_press_and_release("ui_focus_next")
+				get_tree().set_input_as_handled()
+				in_focus_mode_handler = false
+				return
 	if event is InputEventScreenTouch:
 		get_tree().set_input_as_handled()
 		if touch_index and event.index != touch_index:
@@ -234,7 +294,7 @@ func _process(delta):
 	):
 		touch_stop_time = null
 		if tap_count == 2:
-			press_and_release("ui_accept")
+			_press_and_release("ui_accept")
 		tap_count = 0
 	if focus_restore_timer and focus_restore_timer.time_left <= 0:
 		var focus = find_focusable_control(get_tree().root)