Merge pull request #214 from abadger/fix-edit-change-signal

Emit postchange after text is updated

2 files changed, 24 insertions, 7 deletions

diff --git a/urwid/widget.py b/urwid/widget.py
index 9a732e7..98c1905 100644
--- a/urwid/widget.py
+++ b/urwid/widget.py
@@ -1101,11 +1101,22 @@ class Edit(Text):
     deletion.  A caption may prefix the editing area.  Uses text class
     for text layout.
 
-    Users of this class to listen for ``"change"`` events
-    sent when the value of edit_text changes.  See :func:``connect_signal``.
+    Users of this class may listen for ``"change"`` or ``"postchange"``
+    events.  See :func:``connect_signal``.
+
+    * ``"change"`` is sent just before the value of edit_text changes.
+      It receives the new text as an argument.  Note that ``"change"`` cannot
+      change the text in question as edit_text changes the text afterwards.
+    * ``"postchange"`` is sent after the value of edit_text changes.
+      It receives the old value of the text as an argument and thus is
+      appropriate for changing the text.  It is possible for a ``"postchange"``
+      event handler to get into a loop of changing the text and then being
+      called when the event is re-emitted.  It is up to the event
+      handler to guard against this case (for instance, by not changing the
+      text if it is signaled for for text that it has already changed once).
     """
     # (this variable is picked up by the MetaSignals metaclass)
-    signals = ["change"]
+    signals = ["change", "postchange"]
 
     def valid_char(self, ch):
         """
@@ -1160,6 +1171,7 @@ class Edit(Text):
         self.allow_tab = allow_tab
         self._edit_pos = 0
         self.set_caption(caption)
+        self._edit_text = ''
         self.set_edit_text(edit_text)
         if edit_pos is None:
             edit_pos = len(edit_text)
@@ -1355,9 +1367,11 @@ class Edit(Text):
         text = self._normalize_to_caption(text)
         self.highlight = None
         self._emit("change", text)
+        old_text = self._edit_text
         self._edit_text = text
         if self.edit_pos > len(text):
             self.edit_pos = len(text)
+        self._emit("postchange", old_text)
         self._invalidate()
 
     def get_edit_text(self):
diff --git a/urwid/wimp.py b/urwid/wimp.py
index 25e70c1..ea73fb4 100755
--- a/urwid/wimp.py
+++ b/urwid/wimp.py
@@ -109,7 +109,7 @@ class CheckBox(WidgetWrap):
     # allow users of this class to listen for change events
     # sent when the state of this widget is modified
     # (this variable is picked up by the MetaSignals metaclass)
-    signals = ["change"]
+    signals = ["change", 'postchange']
 
     def __init__(self, label, state=False, has_mixed=False,
              on_state_change=None, user_data=None):
@@ -121,7 +121,7 @@ class CheckBox(WidgetWrap):
                                 function call for a single callback
         :param user_data: user_data for on_state_change
 
-        Signals supported: ``'change'``
+        Signals supported: ``'change'``, ``"postchange"``
 
         Register signal handler with::
 
@@ -233,7 +233,8 @@ class CheckBox(WidgetWrap):
 
         # self._state is None is a special case when the CheckBox
         # has just been created
-        if do_callback and self._state is not None:
+        old_state = self._state
+        if do_callback and old_state is not None:
             self._emit('change', state)
         self._state = state
         # rebuild the display widget with the new state
@@ -241,6 +242,8 @@ class CheckBox(WidgetWrap):
             ('fixed', self.reserve_columns, self.states[state] ),
             self._label ] )
         self._w.focus_col = 0
+        if do_callback and old_state is not None:
+            self._emit('postchange', old_state)
 
     def get_state(self):
         """Return the state of the checkbox."""
@@ -335,7 +338,7 @@ class RadioButton(CheckBox):
         This function will append the new radio button to group.
         "first True" will set to True if group is empty.
 
-        Signals supported: ``'change'``
+        Signals supported: ``'change'``, ``"postchange"``
 
         Register signal handler with::