[orca] Add customization to check for AT-SPI2 registry crash and shutdown if detected

[Joanmarie Diggs <joanied src gnome org>]

commit 2dba547bcae49f25649c185498d402776a464ea5
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Mon May 30 23:49:11 2016 -0400

    Add customization to check for AT-SPI2 registry crash and shutdown if detected
    
    It appears that Orca may hang when the AT-SPI2 registry crashes. What is
    triggering the registry crash needs to be figured out. In the meantime,
    it's better to shutdown (and announce that we are doing so) than to hang.
    
    Note that because this is a hack, and an in-progress one at that, polling
    to verify the registry is still alive is disabled by default. It can be
    enabled at the moment by adding the following lines to orca_customizations.py:
    
    import orca.settings
    orca.settings.checkForRegistryCrash = True
    
    Note that this customization may change or go away at any time.

 src/orca/orca.py       |   32 ++++++++++++++++++++++++++++++++
 src/orca/orca_state.py |    2 ++
 src/orca/settings.py   |    3 +++
 3 files changed, 37 insertions(+), 0 deletions(-)
---
diff --git a/src/orca/orca.py b/src/orca/orca.py
index 7e3c76c..eb4ce86 100644
--- a/src/orca/orca.py
+++ b/src/orca/orca.py
@@ -38,6 +38,8 @@ import signal
 import subprocess
 import sys
 
+from gi.repository import GLib
+
 try:
     from gi.repository.Gio import Settings
     a11yAppSettings = Settings(schema_id='org.gnome.desktop.a11y.applications')
@@ -686,6 +688,30 @@ def abortOnSignal(signum, frame):
                   % signum)
     die(signum)
 
+def _getRegistryPIDs(uid):
+    try:
+        output = subprocess.check_output('pgrep -f at-spi2-registryd -u %s' % uid, shell=True)
+        pids = [int(p) for p in output.split()]
+    except:
+        msg = 'ERROR: Could not obtain registry PID'
+        debug.println(debug.LEVEL_INFO, msg, True)
+        return []
+
+    msg = 'ORCA: Registry PIDs FOR user id %s: %s' % (uid, pids)
+    debug.println(debug.LEVEL_INFO, msg, True)
+    return pids
+
+def _checkRegistry():
+    pids = _getRegistryPIDs(os.getuid())
+    if pids and orca_state.registryPID in pids:
+        return True
+
+    msg = 'FATAL: Registry PID %s is not in Registry PIDs for user %s' % (orca_state.registryPID, pids)
+    debug.println(debug.LEVEL_INFO, msg, True)
+    shutdown()
+
+    return False
+
 def main(cacheValues=True):
     """The main entry point for Orca.  The exit codes for Orca will
     loosely be based on signals, where the exit code will be the
@@ -709,6 +735,12 @@ def main(cacheValues=True):
         _settingsManager.setAccessibility(True)
 
     init(pyatspi.Registry)
+    registryPIDs = _getRegistryPIDs(os.getuid())
+    if registryPIDs:
+        orca_state.registryPID = registryPIDs[-1]
+
+    if settings.checkForRegistryCrash:
+        GLib.timeout_add(100, _checkRegistry)
 
     try:
         message = messages.START_ORCA
diff --git a/src/orca/orca_state.py b/src/orca/orca_state.py
index bb8bd49..8cff0fb 100644
--- a/src/orca/orca_state.py
+++ b/src/orca/orca_state.py
@@ -76,3 +76,5 @@ learnModeEnabled = False
 orcaOS = None
 
 listNotificationsModeEnabled = False
+
+registryPID = None
diff --git a/src/orca/settings.py b/src/orca/settings.py
index 2b1ffc3..8d054ee 100644
--- a/src/orca/settings.py
+++ b/src/orca/settings.py
@@ -376,3 +376,6 @@ layoutMode = True
 
 rewindAndFastForwardInSayAll = False
 structNavInSayAll = False
+
+# NOTE: This is temporary and could change or vanish at any time.
+checkForRegistryCrash = False