[Qt-qml] Settings / State Saving proposal for QML

[João Abecasis]

Adriano Rezende wrote:
> 2011/11/17 João Abecasis <joao.abecasis at nokia.com>:
>> The API is pretty minimal, here's example usage:
>> 
>>    Rectangle {
>>        id: main
>>        height: 480
>>        width: 640
>>        color: settings.color
>> 
>>        Settings {
>>            id: settings
>>            property string color: "blue"
>>            property alias height: main.height
>>            property alias width: main.width
>>        }
>>    }
>> 
>> I pushed the code to a clone of the Desktop Components repository over on gitorious. There's some further information in the commit message:
>> 
>>    https://qt.gitorious.org/~biochimia/qt-components/biochimias-desktop/commit/c1ac32929065f24783f4d254d1786dce8202b274
>> 
>> While this needs further refinement and exploration (e.g., ignore the fact that it is using QSettings underneath ;-), what do people around here think of this approach?
> 
> I like the API and the alias approach. It's very handy to keep simple
> data persistence.
> 
> I think the implementation needs just some adjustments though; if the
> object dies before the 500 ms, which is the storage delay, the data is
> not stored on disk. Basically, calling store() in the destructor would
> be enough, but that would not work with aliases depending on the
> object hierarchy. So you need to cache the data or just remove the
> delay, which is also ok I think, since QSettings already merge updates
> behind the scenes.

It's a known issue. Width and height get changed to 0 (zero) before the destructor is called (I get notifications for those changes as well), making the example useless.

Another issue that I just realized is open is validation of settings when reading from external sources. For now, only the type is checked.

Cheers,


João