[core/theme] add xresources support

add support for reading foreground and background, and colors, from
xresources.py

many thanks to @Aliuakbar for the addition!

fixes #731

bumblebee_status/core/theme.py

@@ -7,6 +7,7 @@ import glob
 
 import core.event
 import util.algorithm
+import util.xresources
 
 log = logging.getLogger(__name__)
 
@@ -89,12 +90,20 @@ class Theme(object):
         try:
             if isinstance(name, dict):
                 return name
+
+            result = {}
             if name.lower() == "wal":
                 wal = self.__load_json("~/.cache/wal/colors.json")
-                result = {}
                 for field in ["special", "colors"]:
                     for key in wal.get(field, {}):
                         result[key] = wal[field][key]
+            if name.lower() == "xresources":
+                for key in ("background", "foreground"):
+                    result[key] = xresources.query(key)
+                for i in range(16):
+                    key = color + str(i)
+                    result[key] = xresources.query(key)
+
             return result
         except Exception as e:
             log.error("failed to load colors: {}", e)

bumblebee_status/util/xresources.py

@@ -0,0 +1,10 @@
+import subprocess
+import shutil
+
+def query(key):
+    if shutil.which("xgetres"):
+        return subprocess.run(["xgetres", key],
+                capture_output=True).stdout.decode("utf-8").strip()
+    else:
+        raise Exception("xgetres must be installed for this theme")
+