On 09.10.2009 09:32, Adrian Buehlmann wrote:
> On 09.10.2009 04:32, Steve Borho wrote:
>> On Thu, Oct 8, 2009 at 9:10 PM, Yuki KODAMA <endflow....@gmail.com> wrote:
>>> On Fri, Oct 9, 2009 at 11:00, TK Soh <teekay...@gmail.com> wrote:
>>>> On Thu, Oct 8, 2009 at 6:57 PM, Steve Borho <st...@borho.org> wrote:
>>>>> FYI
>>>>>
>>>>> I realized today that we need to explicitly 'return False' from all of our
>>>>> idle_add() callback routines.
>>>>> If the return result evaluates as True, the callback will be called
>>>>> endlessly.
>>>> I haven't checked, but it's not documented in PyGTK doc?
>>> Documented:
>>> "If callback returns FALSE it is automatically removed from the
>>> list of event sources and will not be called again."
>>> http://pygstdocs.berlios.de/pygobject-reference/glib-functions.html#function-glib--idle-add
>> I did verify this by taking a callback and adding a print and
>> returning True.. it gets called hundreds of time per second.
>>
>>> After all, for safety, we should return False explicitly.
>> The wrapper class Adrian suggested feels too heavy weight. A lambda
>> wouldn't be too bad, but simply returning False I feel would be the
>> most clear. It's good to know Python is saving us from obvious bugs.
>
> IMHO, adding 'return False' randomly in functions that happen to be
> used in idle_add is confusing and suboptimal for maintenance.
>
> We could package my approach in a function for example in
> hgtk.gtklib:
>
> def idle_add(f):
> class single_call(object):
> def __init__(self, f):
> self.f = f
> def __call__(self):
> self.f()
> return False
> gobject.idle_add(single_call(f))
>
> and then use it like this (example):
>
> gtklib.idle_add(self.realize_settings)
>
> This approach is even extensible, as it would allow to add
> parameters (which would be kept in the single_call object
> until f is called, just add an '*args').
>
> And it can be applied to every function.
Actually, I just found out that we do need parameters, so we would
need something like:
diff --git a/tortoisehg/hgtk/gtklib.py b/tortoisehg/hgtk/gtklib.py
--- a/tortoisehg/hgtk/gtklib.py
+++ b/tortoisehg/hgtk/gtklib.py
@@ -604,3 +604,22 @@ def hasspellcheck():
return True
except ImportError:
return False
+
+def idle_add(f, *args):
+ '''wrap function f for gobject.idle_add, so that f is guaranteed to be
+ called only once, independent of its return value'''
+
+ class single_call(object):
+ def __init__(self, f, args):
+ self.f = f
+ self.args = args
+ def __call__(self):
+ self.f(*args) # ignore return value of f
+ return False # return False to signal: don't call us again
+
+ # functions passed to gobject.idle_add must return False, or they
+ # will be called repeatedly. The single_call object wraps f and always
+ # returns False when called. So the return value of f doesn't matter,
+ # it can even return True (which would lead to gobject.idle_add
+ # calling the function again, if used without single_call).
+ gobject.idle_add(single_call(f, args))
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