Add SayoDevice support, 15 key pads and theme styles

Second protocol family (8089:000b) behind a new backend seam, 15 key and 3 knob pads, Knobs North plus the style and colour grid, Windows import fix, window resize fix.

macropad_gui/actions.py

@@ -20,7 +20,6 @@ the desktop; it just gets a copy.
 """
 
 import errno
-import fcntl
 import glob
 import json
 import os
@@ -31,6 +30,14 @@ import signal
 import subprocess
 import sys
 import time
+
+try:
+    import fcntl
+except ImportError:
+    # Windows has none. Everything that needs it is Linux only anyway, and
+    # each use checks. Importing this module must not fail, because app.py
+    # imports it to build the window.
+    fcntl = None
 from dataclasses import dataclass
 from pathlib import Path
 
@@ -265,9 +272,17 @@ class VirtualKeyboard:
     and the first paste would otherwise go missing.
     """
 
-    def __init__(self, path=UINPUT, _open=os.open, _ioctl=fcntl.ioctl,
+    def __init__(self, path=UINPUT, _open=os.open, _ioctl=None,
                  _write=os.write, _sleep=time.sleep):
         import struct
+        # Resolved here, not in the signature: a default argument is
+        # evaluated when the module is imported, which on Windows would
+        # crash before the window ever got a chance to open.
+        if _ioctl is None:
+            if fcntl is None:
+                raise OSError("a virtual keyboard needs /dev/uinput, which "
+                              "this system hasn't got")
+            _ioctl = fcntl.ioctl
         self._struct, self._write, self._sleep = struct, _write, _sleep
         self.fd = _open(path, os.O_WRONLY | os.O_NONBLOCK)
         _ioctl(self.fd, _UI_SET_EVBIT, _EV_KEY)
@@ -570,6 +585,10 @@ def listen(debug=False, log=print):
     """
     lock_path = runtime_dir() / LOCK
     lock_path.parent.mkdir(parents=True, exist_ok=True)
+    if fcntl is None:
+        log("Background actions are Linux only for now: they need /dev/uinput "
+            "to type, and a file lock to keep one copy running.")
+        return 1
     lock = open(lock_path, "a+")
     try:
         fcntl.flock(lock, fcntl.LOCK_EX | fcntl.LOCK_NB)