jralls at ceridwen.us
Sat Feb 16 15:59:37 EST 2013
On Feb 16, 2013, at 12:30 PM, Herbert Thoma <herbert.thoma at iis.fraunhofer.de> wrote:
> Am 16.02.2013 17:06, schrieb John Ralls:
>> On Feb 16, 2013, at 5:06 AM, Herbert Thoma <herbert.thoma at iis.fraunhofer.de> wrote:
>>> forgot CC list ...
>>> Am 15.02.2013 21:06, schrieb John Ralls:
>>>>>> Why hard to say? MVC isn't exactly cutting-edge design. It's been
>>>>>> around since 1988 and 7 years later GoF thought it so well-understood
>>>>>> that it's the "how to use patterns" example in the introduction.
>>>>> Well, the point is that every time the user leaves a field you need to
>>>>> parse all the input fields and process them in the controller/model as
>>>>> part of the validation, even if the user hasn't asked to 'save' yet.
>>>>> I guess it all depends on your controller APIs. (In the RoR world this
>>>>> is harder to do, because the view is in the browser, but the model and
>>>>> controllers are on the server -- and there is no "verify this model" API
>>>>> in the controller. At least not directly. The client-side-validations
>>>>> gem adds some support for this).
>>>> We already do that for the account type listbox: We connect to a signal
>>>> (don't know offhand which one) in the parent accounts GtkTreeView that tells
>>>> us that the user has selected a parent account, retrieve that account, run
>>>> xaccAccountGetCompatibleTypes() on it, and populate the account type listbox
>>>> with the result.
>>>> That's a pretty standard way for UI View objects to communicate with their
>>>> controller objects, though there are others. Wx has a specific "Validator"
>>>> class that lets you register a callback to test control input as it happens.
>>>> It also has a signals mechanism (which they rather confusingly call Events)
>>>> to support other interactivity needs. Qt is well-known for its "signals and slots"
>>>> feature, which I imagine is used for this purpose much like Gtk's signals are, but
>>>> I've never written anything for Qt so I don't actually know.
>>> Yes, you can use signals and slots this way. I personally like Qt very much. For me
>>> it is the best GUI toolkit I have ever worked with (I worked with Motif, MFC,
>>> GTK and Qt, but always only small projects or patches to GnuCash).
>>> However, I would still be hesitant to use signals and slots in the engine. Earlier
>>> in this thread it was stated that the engine depends heavily on Glib and that this
>>> is bad for portability. Do we want to replace the Glib dependency with a Qt
>> See Geert's and my responses about where the "slots" go.
> OK, thanks. I think I got it. I only just know enough C++ to be dangerous ...
>> Does Qt have another mechanism for validating user input as he types? How does it handle spell checking? ("Magic" is a reasonable answer here: I know in detail how Gtk handles spell checking because it's an add-on that I've contributed to, but Apple handles it inside the toolkit so that application devs needn't do anything about it.)
> Qt has a QValidator class. http://qt-project.org/doc/qt-4.8/qvalidator.html
> I don't think that this is used for spell checking, though.
Looks similar to Wx's.
It also links to http://qt-project.org/doc/qt-4.8/widgets-lineedits.html which shows signals and slots being used to perform the interactive features we've been discussing. They're even used to fire off the validator.
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