restore KeyCodesFilter, somehow dropped during refactoring

subiquity/core.py

@@ -31,6 +31,7 @@ from subiquitycore.async_helpers import (
     run_in_thread,
     schedule_task,
     )
+from subiquitycore.screen import is_linux_tty
 from subiquitycore.tuicontroller import Skip
 from subiquitycore.tui import TuiApplication
 from subiquitycore.snapd import (
@@ -45,6 +46,10 @@ from subiquity.common.errorreport import (
     ErrorReportKind,
     )
 from subiquity.journald import journald_listener
+from subiquity.keycodes import (
+    DummyKeycodesFilter,
+    KeyCodesFilter,
+    )
 from subiquity.lockfile import Lockfile
 from subiquity.models.subiquity import SubiquityModel
 from subiquity.ui.frame import SubiquityUI
@@ -124,6 +129,11 @@ class Subiquity(TuiApplication):
         if not opts.bootloader == 'none' and platform.machine() != 's390x':
             self.controllers.remove("Zdev")
 
+        if is_linux_tty():
+            self.input_filter = KeyCodesFilter()
+        else:
+            self.input_filter = DummyKeycodesFilter()
+
         self.journal_fd, self.journal_watcher = journald_listener(
             ["subiquity"], self.subiquity_event, seek=True)
         self.help_menu = HelpMenu(self)
@@ -266,6 +276,9 @@ class Subiquity(TuiApplication):
         super().new_event_loop()
         self.aio_loop.add_reader(self.journal_fd, self.journal_watcher)
 
+    def extra_urwid_loop_args(self):
+        return dict(input_filter=self.input_filter.filter)
+
     def run(self):
         try:
             if self.opts.autoinstall is not None:

subiquity/keycodes.py

@@ -0,0 +1,108 @@
+# Copyright 2020 Canonical, Ltd.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import fcntl
+import logging
+import os
+import struct
+import sys
+
+log = logging.getLogger('subiquity.keycodes')
+
+# /usr/include/linux/kd.h
+K_RAW = 0x00
+K_XLATE = 0x01
+K_MEDIUMRAW = 0x02
+K_UNICODE = 0x03
+K_OFF = 0x04
+
+KDGKBMODE = 0x4B44  # gets current keyboard mode
+KDSKBMODE = 0x4B45  # sets current keyboard mode
+
+
+class KeyCodesFilter:
+    """input_filter that can pass (medium) raw keycodes to the application
+
+    See http://lct.sourceforge.net/lct/x60.html for terminology.
+
+    Call enter_keycodes_mode()/exit_keycodes_mode() to switch into and
+    out of keycodes mode. In keycodes mode, the only events passed to
+    the application are "press $N" / "release $N" where $N is the
+    keycode the user pressed or released.
+
+    Much of this is cribbed from the source of the "showkeys" utility.
+    """
+
+    def __init__(self):
+        self._fd = os.open("/proc/self/fd/"+str(sys.stdin.fileno()), os.O_RDWR)
+        self.filtering = False
+
+    def enter_keycodes_mode(self):
+        log.debug("enter_keycodes_mode")
+        self.filtering = True
+        # Read the old keyboard mode (it will proably always be K_UNICODE but
+        # well).
+        o = bytearray(4)
+        fcntl.ioctl(self._fd, KDGKBMODE, o)
+        self._old_mode = struct.unpack('i', o)[0]
+        # Set the keyboard mode to K_MEDIUMRAW, which causes the keyboard
+        # driver in the kernel to pass us keycodes.
+        fcntl.ioctl(self._fd, KDSKBMODE, K_MEDIUMRAW)
+
+    def exit_keycodes_mode(self):
+        log.debug("exit_keycodes_mode")
+        self.filtering = False
+        fcntl.ioctl(self._fd, KDSKBMODE, self._old_mode)
+
+    def filter(self, keys, codes):
+        # Luckily urwid passes us the raw results from read() we can
+        # turn into keycodes.
+        if self.filtering:
+            i = 0
+            r = []
+            n = len(codes)
+            while i < len(codes):
+                # This is straight from showkeys.c.
+                if codes[i] & 0x80:
+                    p = 'release '
+                else:
+                    p = 'press '
+                if i + 2 < n and (codes[i] & 0x7f) == 0:
+                    if (codes[i + 1] & 0x80) != 0:
+                        if (codes[i + 2] & 0x80) != 0:
+                            kc = (((codes[i + 1] & 0x7f) << 7) |
+                                  (codes[i + 2] & 0x7f))
+                            i += 3
+                else:
+                    kc = codes[i] & 0x7f
+                    i += 1
+                r.append(p + str(kc))
+            return r
+        else:
+            return keys
+
+
+class DummyKeycodesFilter:
+    # A dummy implementation of the same interface as KeyCodesFilter
+    # we can use when not running in a linux tty.
+
+    def enter_keycodes_mode(self):
+        pass
+
+    def exit_keycodes_mode(self):
+        pass
+
+    def filter(self, keys, codes):
+        return keys