From a9394222c323143c0fea03848a3f1daf79017a00 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Fri, 2 Nov 2012 12:11:41 +0100
Subject: [PATCH] properly open and close processes

---
 dsl.py             | 19 +++++++++++++------
 gui.py             |  7 ++++++-
 zenity_dialogue.py |  7 +++----
 3 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/dsl.py b/dsl.py
index 890ea70..d13d0a0 100755
--- a/dsl.py
+++ b/dsl.py
@@ -78,13 +78,24 @@ def loadConfigFile(file):
 	# add some convencience get functions
 	return result
 
+# helper function: execute a process, return output as iterator, throw exception if there was an error
+# you *must* iterate to the end if you use this!
+def processOutputGen(*args):
+	p = subprocess.Popen(args, stdout=subprocess.PIPE)
+	for line in p.stdout:
+		yield line
+	p.wait() # wait for process to exit (it closed stdout, so it can't block anymore)
+	if p.returncode != 0:
+		raise Exception("Error executing "+str(args))
+def processOutputIt(*args):
+	return list(processOutputGen(*args)) # list() iterates over the generator
+
 # Run xrandr and return a dict of output names mapped to lists of available resolutions, each being a (width, height) pair.
 # An empty list indicates that the connector is disabled.
 def getXrandrInformation():
-	p = subprocess.Popen(["xrandr", "-q"], stdout=subprocess.PIPE)
 	connectors = {} # map of connector names to a list of resolutions
 	connector = None # current connector
-	for line in p.stdout:
+	for line in processOutputGen("xrandr", "-q"):
 		# screen?
 		m = re.search(r'^Screen [0-9]+: ', line)
 		if m is not None: # ignore this line
@@ -107,10 +118,6 @@ def getXrandrInformation():
 		# not fatal as my xrandr shows strange stuff when a display is enabled, but not connected
 		#raise Exception("Unknown line in xrandr output:\n"+line)
 		print "Warning: Unknown xrandr line %s" % line
-	# be sure to always proprly finish up with the xrandr
-	p.communicate()
-	# if everything succeededso far, check return code
-	if p.returncode != 0: raise Exception("Querying xrandr for data failed.")
 	return connectors
 
 # convert a (width, height) pair into a string accepted by xrandr as argument for --mode
diff --git a/gui.py b/gui.py
index b3929cb..6dabe0f 100644
--- a/gui.py
+++ b/gui.py
@@ -39,7 +39,12 @@ def qtAvailable():
 		return False
 
 def zenityAvailable():
-	return True # FIXME
+	try:
+		from dsl import processOutputIt
+		processOutputIt("zenity", "--version")
+		return True
+	except Exception:
+		return False
 
 # actual frontends
 if qtAvailable():
diff --git a/zenity_dialogue.py b/zenity_dialogue.py
index 69365e8..60d7827 100644
--- a/zenity_dialogue.py
+++ b/zenity_dialogue.py
@@ -15,14 +15,13 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 
-import subprocess
-from dsl import RelativeScreenPosition, ScreenSetup, res2user
+from dsl import RelativeScreenPosition, ScreenSetup, res2user, processOutputIt
 
 def userChoose (title, choices, returns, fallback):
 	assert len(choices) == len(returns)
-	p = subprocess.Popen(["zenity", "--list", "--text="+title, "--column="]+choices, stdout=subprocess.PIPE)
+	args = ["zenity", "--list", "--text="+title, "--column="]+choices
 	switch = dict (zip (choices,returns))
-	for line in p.stdout: # FIXME use p.communicate()[0] instead to get entire stdout and ensure the process terminates. also check p.returncode.
+	for line in processOutputIt(*args):
 		return switch.get(line.strip(), fallback)
 	return fallback
 
-- 
2.30.2