Small BRLTTY driver improvements

* Mark the BRLTTY braille display driver as thread safe
* Improve availability check for BRLTTY braille display driver: only report as available if a named pipe for BrlAPI is present
* Add more BRLTTY key bindings (nvaccess#6483):
  * learn: toggle NVDA input help
  * prefmenu: open the NVDA menu
  * prefload/prefsave: Load/save NVDA configuration
  * time: Show time
  * say_line: Speak the current line where the review cursor is located
  * say_below: Say all using review cursor

source/brailleDisplayDrivers/brltty.py

@@ -1,9 +1,9 @@
-#brailleDisplayDrivers/brltty.py
-#A part of NonVisual Desktop Access (NVDA)
-#This file is covered by the GNU General Public License.
-#See the file COPYING for more details.
-#Copyright (C) 2008-2019 NV Access Limited, Babbage B.V>
+# A part of NonVisual Desktop Access (NVDA)
+# This file is covered by the GNU General Public License.
+# See the file COPYING for more details.
+# Copyright (C) 2008-2023 NV Access Limited, Babbage B.V, Bram Duvigneau
 
+import os
 import time
 import wx
 import braille
@@ -21,18 +21,38 @@
 
 KEY_CHECK_INTERVAL = 50
 
+# BRLAPI named pipes for local connections are numbered and all start with a common name.
+# This name is set on compile time and should be the same for all BRLTTY releases,
+# however, if a user compiles their own version this may differ
+BRLAPI_NAMED_PIPE_PREFIX = "BrlAPI"
+
 class BrailleDisplayDriver(braille.BrailleDisplayDriver):
 	"""brltty braille display driver.
 	"""
 	name = "brltty"
 	description = "brltty"
+	isThreadSafe = True
+
+	@classmethod
+	def _get_brlapi_pipes(cls) -> List[str]:
+		"""Get the BrlAPI named pipes
+
+		Every BRLTTY instance with the BrlAPI enabled will have it's own named pipe to accept API connections.
+		The brlapi.Connection constructor takes either a `host:port` argument or just `:port`.
+		If only a port is given, this corresponds to the number at the end of the named pipe.
+		"""
+		return [pipe.name for pipe in os.scandir("//./pipe/") if pipe.name.startswith(BRLAPI_NAMED_PIPE_PREFIX)]
 
 	@classmethod
 	def check(cls):
-		return bool(brlapi)
+		if not bool(brlapi):
+			return False
+		# Since this driver only supports local connections for now,
+		# we can mark it as unavailable if there are no BrlAPI named pipes present
+		return bool(cls.brlapi_pipes)
 
 	def __init__(self):
-		super(BrailleDisplayDriver, self).__init__()
+		super().__init__()
 		self._con = brlapi.Connection()
 		self._con.enterTtyModeWithPath()
 		self._keyCheckTimer = wx.PyTimer(self._handleKeyPresses)
@@ -42,7 +62,7 @@ def __init__(self):
 		self._con.ignoreKeys(brlapi.rangeType_type, (brlapi.KEY_TYPE_SYM,))
 
 	def terminate(self):
-		super(BrailleDisplayDriver, self).terminate()
+		super().terminate()
 		# Exceptions might be raised if initialisation failed. Just ignore them.
 		try:
 			self._keyCheckTimer.Stop()
@@ -100,6 +120,13 @@ def _onKeyPress(self, key):
 			"braille_previousLine": ("br(brltty):lnup",),
 			"braille_nextLine": ("br(brltty):lndn",),
 			"braille_routeTo": ("br(brltty):route",),
+			"toggleInputHelp": ("brl(brltty):learn"),
+			"showGui": ("brl(brltty):prefmenu",),
+			"revertConfiguration": ("brl(brltty):prefload",),
+			"saveConfiguration": ("brl(brltty):prefsave",),
+			"dateTime": ("brl(brltty):time",),
+			"review_currentLine": ("brl(brltty):say_line",),
+			"review_sayAll": ("brl(brltty):say_below",),
 		}
 	})
 
@@ -108,7 +135,7 @@ class InputGesture(braille.BrailleDisplayGesture):
 	source = BrailleDisplayDriver.name
 
 	def __init__(self, model, command, argument):
-		super(InputGesture, self).__init__()
+		super().__init__()
 		self.model = model
 		self.id = BRLAPI_CMD_KEYS[command]
 		if command == brlapi.KEY_CMD_ROUTE: