only perform color lookup for colored terminals

2 files changed, 14 insertions, 12 deletions

diff --git a/blessings/__init__.py b/blessings/__init__.py
index 9d37889..ca6a035 100644
--- a/blessings/__init__.py
+++ b/blessings/__init__.py
@@ -385,6 +385,8 @@ class Terminal(object):
         # bright colors at 8-15:
         offset = 8 if 'bright_' in color else 0
         base_color = color.rsplit('_', 1)[-1]
+        if self.number_of_colors == 0:
+            return NullCallableString()
         return self._formatting_string(
             color_cap(getattr(curses, 'COLOR_' + base_color.upper()) + offset))
 
diff --git a/blessings/tests.py b/blessings/tests.py
index 7dda746..a61b73e 100644
--- a/blessings/tests.py
+++ b/blessings/tests.py
@@ -137,23 +137,23 @@ def test_null_fileno():
 
 def test_mnemonic_colors():
     """Make sure color shortcuts work."""
-    def color(num):
-        return unicode_parm('setaf', num)
+    def color(t, num):
+        return t.number_of_colors and unicode_parm('setaf', num) or ''
 
-    def on_color(num):
-        return unicode_parm('setab', num)
+    def on_color(t, num):
+        return t.number_of_colors and unicode_parm('setab', num) or ''
 
     # Avoid testing red, blue, yellow, and cyan, since they might someday
     # change depending on terminal type.
     t = TestTerminal()
-    eq_(t.white, color(7))
-    eq_(t.green, color(2))  # Make sure it's different than white.
-    eq_(t.on_black, on_color(0))
-    eq_(t.on_green, on_color(2))
-    eq_(t.bright_black, color(8))
-    eq_(t.bright_green, color(10))
-    eq_(t.on_bright_black, on_color(8))
-    eq_(t.on_bright_green, on_color(10))
+    eq_(t.white, color(t, 7))
+    eq_(t.green, color(t, 2))  # Make sure it's different than white.
+    eq_(t.on_black, on_color(t, 0))
+    eq_(t.on_green, on_color(t, 2))
+    eq_(t.bright_black, color(t, 8))
+    eq_(t.bright_green, color(t, 10))
+    eq_(t.on_bright_black, on_color(t, 8))
+    eq_(t.on_bright_green, on_color(t, 10))
 
 
 def test_callable_numeric_colors():