Geert a écrit :
> Hi Alain, this sounds very interesting.
thanks
> I have never been a big fan of the
> current "Preference Browser".
The main problem with current preference system is that it makes uses of
globals (declared in the class side of Preferences) and that a lot of
packages depend on it.
The main goal of the refactoring is to make preferences local to the
packages in which they are declared.
Current preference browser is not that bad and could be reused.
> I am now trying to grasp (still learning
> here) how this new "Pharo Preference Mechanism" works.It would be great if
> the mechanism could be explained in detail in something like the new Pharo
> By Example manual :)
>
Each preference is stored by a PreferenceValue instance and each time a
PreferenceValue is updated (with a #value: message sent) an event is
sent to the class which defines the preference. The event sending is
standard:
PreferenceValue>>value: anObject
realValue ~= anObject
ifTrue: [realValue := anObject.
location triggerEvent: selector with: anObject]
realValue is the instance variable wich stores current preference value.
location is the class which declares the preference
selector is the selector of the preference (i.e. #gradientButtonLook)
So my proposition is to declare a preference locally. Let's take the
example of freetype monitorTypeLCD preference.
If we implement it the way it is now, as a boolean, it could be:
---------------
FreeTypeSettings class>>monitorTypeLCD
<preference: 'LCD monitor type' type: #Boolean set: #monitorTypeLCD:
defaultValue: false description: 'Use of a LCD...'>
^ MonitorTypeLCD
ifNil: [MonitorTypeLCD := PreferenceValue value: false location:
self selector: #monitorTypeLCD]
FreeTypeSettings class>>monitorTypeLCD: aBoolean
self monitorTypeLCD value: hintingFull
FreeTypeSettings class>>initialize
FreeTypeSettings when: #monitorTypeLCD send:
#monitorTypeLCDPreferenceChanged: to: self.
FreeTypeSettings class>>monitorTypeLCDPreferenceChanged: aBoolean
self current monitorTypeLCDPreferenceChanged: aBoolean
-------------
The pragma you see in FreeTypeSettings class>>monitorTypeLCD in only
here for UI tools such as PreferenceBrowser.
If a client object needs monitorTypeLCD value, it asks directly to its
provider which is FreeTypeSettings class:
...
useLCD := FreeTypeSettings monitorTypeLCD value.
...
but note that such a preference should be set as a choice between two
values #LCD or #CRT...
hope things are a little bit clearer now.
alain
>
> Alain Plantec wrote:
>
>> I've joined 4 packages :
>> - PrefCore contains PreferenceValue which is now the only mandatory class.
>>
>> 2 packages for testing:
>> - PrefProvider contains PrefProvider class which declares some preferences
>> - PrefUser contains PrefChangeListener (try PrefChangeListener test).
>>
>> 1 package for UI:
>> - PrefTool contains PreferenceCollector and PreferenceDefinition. They
>> are optional.
>>
>>
>
>
_______________________________________________
Pharo-project mailing list
[email protected]
http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
