Only format widgets when it's time to write

This saves a lot of CPU time when there's a lot of updates
during an update period. Obnam, for example, does that,
and ttystatus was visible in its benchmarks.

1 files changed, 11 insertions, 10 deletions

diff --git a/ttystatus/status.py b/ttystatus/status.py
index 24f369b..54c6049 100644
--- a/ttystatus/status.py
+++ b/ttystatus/status.py
@@ -77,16 +77,17 @@ class TerminalStatus(object):
     def __setitem__(self, key, value):
         '''Set value for key.'''
         self._values[key] = value
-        width = self._m.width
-        if width != self._latest_width:
-            widgets = self._widgets
-            self._latest_width = width
-        else:
-            widgets = self._interests.get(key, []) + self._wildcards
-        for w in widgets:
-            w.update(self, width)
-            width -= len(str(w))
-        self._m.write(''.join(str(w) for w in self._widgets))
+        if self._m.time_to_write():
+            width = self._m.width
+            if width != self._latest_width:
+                widgets = self._widgets
+                self._latest_width = width
+            else:
+                widgets = self._interests.get(key, []) + self._wildcards
+            for w in widgets:
+                w.update(self, width)
+                width -= len(str(w))
+            self._m.write(''.join(str(w) for w in self._widgets))
     
     def increase(self, key, delta):
         '''Increase value for a key by a given amount.'''