Adding support for CPU graph in FreeBSD

This commit adds support for CPUGraph in FreeBSD. And to make tests
complete in FreeBSD I also added support for the MemoryGraph.

There are other means of getting cpu and mem stats, but this is the
most similar to the vanilla graph.

For this to work in FreeBSD linprocfs needs to be mounted.

Since linprocfs uses an older model of the kernel not all
fields are available, hence removing some of the fields
for FreeBSD.

In FreeBSD /proc stuff is located in
/compat/linux/proc , but it lacks some of the features
of a modern linux kernel. Hence the platform.system(checks).

This should maintain compatibility with Linux, but please test
it so I don't break anything.

Cheers!

Closes #796

libqtile/widget/graph.py

@@ -36,6 +36,7 @@
 from . import base
 from os import statvfs
 import time
+import platform
 
 __all__ = [
     'CPUGraph',
@@ -200,7 +201,11 @@ def __init__(self, **config):
         self.oldvalues = self._getvalues()
 
     def _getvalues(self):
-        with open('/proc/stat') as file:
+        proc = '/proc/stat'
+        if platform.system() == "FreeBSD":
+            proc = '/compat/linux' + proc
+
+        with open(proc) as file:
             lines = file.readlines()
 
             # default to all cores (first line)
@@ -214,8 +219,10 @@ def _getvalues(self):
 
                 if not line.startswith("cpu%s" % self.core):
                     raise ValueError("No such core: %s" % self.core)
-
-            name, user, nice, sys, idle, iowait, tail = line.split(None, 6)
+            if platform.system() == 'FreeBSD':
+                name, user, nice, sys, idle = line.split(None, 4)
+            else:
+                name, user, nice, sys, idle, iowait, tail = line.split(None, 6)
 
             return (int(user), int(nice), int(sys), int(idle))
 
@@ -237,12 +244,19 @@ def update_graph(self):
 
 
 def get_meminfo():
-    with open('/proc/meminfo') as file:
-        val = {}
+    val = {}
+    proc = '/proc/meminfo'
+    if platform.system() == "FreeBSD":
+        proc = "/compat/linux" + proc
+    with open(proc) as file:
         for line in file:
-            key, tail = line.split(':')
-            uv = tail.split()
-            val[key] = int(uv[0])
+            if line.lstrip().startswith("total"):
+                pass
+            else:
+                key, tail = line.strip().split(':')
+                uv = tail.split()
+                val[key] = int(uv[0])
+    val['MemUsed'] = val['MemTotal'] - val['MemFree']
     return val