Patchwork [1/2] Rework how the devshell functions

diff --git a/meta/classes/devshell.bbclass b/meta/classes/devshell.bbclass
index 5f262f4..95c29f3 100644
--- a/meta/classes/devshell.bbclass
+++ b/meta/classes/devshell.bbclass
@@ -1,22 +1,17 @@ 
-do_devshell[dirs] = "${S}"
-do_devshell[nostamp] = "1"
+inherit terminal
 
-XAUTHORITY ?= "${HOME}/.Xauthority"
 
-devshell_do_devshell() {
-	export DISPLAY='${DISPLAY}'
-	export DBUS_SESSION_BUS_ADDRESS='${DBUS_SESSION_BUS_ADDRESS}'
-	export XAUTHORITY='${XAUTHORITY}'
-	export TERMWINDOWTITLE="Bitbake Developer Shell"
-	export EXTRA_OEMAKE='${EXTRA_OEMAKE}'
-	export SHELLCMDS="bash"
-	${TERMCMDRUN}
-	if [ $? -ne 0 ]; then
-	    echo "Fatal: '${TERMCMD}' not found. Check TERMCMD variable."
-	    exit 1
-	fi
+export XAUTHORITY ?= "${HOME}/.Xauthority"
+export SHELL ?= "bash"
+export DBUS_SESSION_BUS_ADDRESS
+export DISPLAY
+export EXTRA_OEMAKE
+
+python do_devshell () {
+    oe_terminal(d.getVar('SHELL', True), 'OpenEmbedded Developer Shell', d)
 }
-addtask devshell after do_patch
 
-EXPORT_FUNCTIONS do_devshell
+addtask devshell after do_patch
 
+do_devshell[dirs] = "${S}"
+do_devshell[nostamp] = "1"
diff --git a/meta/classes/terminal.bbclass b/meta/classes/terminal.bbclass
new file mode 100644
index 0000000..93646f7
--- /dev/null
+++ b/meta/classes/terminal.bbclass
@@ -0,0 +1,30 @@ 
+OE_TERMINAL ?= 'auto'
+OE_TERMINAL[type] = 'choice'
+OE_TERMINAL[choices] = 'auto none \
+                        ${@" ".join(o.name \
+                                    for o in oe.terminal.prioritized())}'
+
+
+def oe_terminal(command, title, d):
+    import oe.data
+    import oe.terminal
+
+    terminal = oe.data.typed_value('OE_TERMINAL', d).lower()
+    if terminal == 'none':
+        bb.fatal('Devshell usage disabled with OE_TERMINAL')
+    elif terminal != 'auto':
+        try:
+            oe.terminal.spawn(terminal, command, title)
+            return
+        except oe.terminal.UnsupportedTerminal:
+            bb.warn('Unsupported terminal "%s", defaulting to "auto"' %
+                    terminal)
+        except oe.terminal.ExecutionError as exc:
+            bb.fatal('Unable to spawn terminal %s: %s' % (terminal, exc))
+
+    try:
+        oe.terminal.spawn_preferred(command, title)
+    except oe.terminal.NoSupportedTerminals:
+        bb.fatal('No valid terminal found, unable to open devshell')
+    except oe.terminal.ExecutionError as exc:
+        bb.fatal('Unable to spawn terminal %s: %s' % (terminal, exc))
diff --git a/meta/lib/oe/terminal.py b/meta/lib/oe/terminal.py
new file mode 100644
index 0000000..5336167
--- /dev/null
+++ b/meta/lib/oe/terminal.py
@@ -0,0 +1,102 @@ 
+import logging
+import os
+import oe.classutils
+import shlex
+from bb.process import Popen, ExecutionError
+
+logger = logging.getLogger('BitBake.OE.Terminal')
+
+
+class UnsupportedTerminal(StandardError):
+    pass
+
+class NoSupportedTerminals(StandardError):
+    pass
+
+
+class Registry(oe.classutils.ClassRegistry):
+    command = None
+
+    def __init__(cls, name, bases, attrs):
+        super(Registry, cls).__init__(name.lower(), bases, attrs)
+
+    @property
+    def implemented(cls):
+        return bool(cls.command)
+
+
+class Terminal(Popen):
+    __metaclass__ = Registry
+
+    def __init__(self, command, title=None):
+        self.format_command(command, title)
+        logger.debug(1, "%s: running %s", self.name, self.command)
+
+        try:
+            Popen.__init__(self, self.command, shell=False)
+        except OSError as exc:
+            import errno
+            if exc.errno == errno.ENOENT:
+                raise UnsupportedTerminal(self.name)
+            else:
+                raise
+
+    def format_command(self, command, title):
+        fmt = {'title': title or 'Terminal', 'command': command}
+        if isinstance(self.command, basestring):
+            self.command = shlex.split(self.command.format(**fmt))
+        else:
+            self.command = [element.format(**fmt) for element in self.command]
+
+class XTerminal(Terminal):
+    def __init__(self, command, title=None):
+        Terminal.__init__(self, command, title)
+        if not os.environ.get('DISPLAY'):
+            raise UnsupportedTerminal(self.name)
+
+class Gnome(XTerminal):
+    command = 'gnome-terminal --disable-factory -t "{title}" -x {command}'
+    priority = 2
+
+class Konsole(XTerminal):
+    command = 'konsole -T "{title}" -e {command}'
+    priority = 2
+
+class XTerm(XTerminal):
+    command = 'xterm -T "{title}" -e {command}'
+    priority = 1
+
+class Rxvt(XTerminal):
+    command = 'rxvt -T "{title}" -e {command}'
+    priority = 1
+
+class Screen(Terminal):
+    command = 'screen -D -m -t "{title}" {command}'
+
+
+def prioritized():
+    return Registry.prioritized()
+
+def spawn_preferred(command, title=None):
+    """Spawn the first supported terminal, by priority"""
+    for terminal in prioritized():
+        try:
+            spawn(terminal.name, command, title)
+            break
+        except UnsupportedTerminal:
+            continue
+    else:
+        raise NoSupportedTerminals()
+
+def spawn(name, command, title=None):
+    """Spawn the specified terminal, by name"""
+    logger.debug(1, 'Attempting to spawn terminal "%s"', name)
+    try:
+        terminal = Registry.registry[name]
+    except KeyError:
+        raise UnsupportedTerminal(name)
+
+    pipe = terminal(command, title)
+    output = pipe.communicate()[0]
+    if pipe.returncode != 0:
+        raise ExecutionError(pipe.command, pipe.returncode, output)