> Question to the list; are there better techniques for exposing properties to
> a common element from a specific implementation - and be able to use such
> properties in the implementation effectively? Can attached properties be used
> for this without breaking the ability to deploy the App to a different
> platform that doesn't have this property?
We could provide some elements to handle these platform specific parts
in a more declarative way, using bindings and connections. A possible
approach would be as follows:
===
Button {
id: button
// active binding when platform is meego
PlatformProperty { target: button; platform: "meego"; name:
"color"; value: "red"; }
// active binding when platform is symbian
PlatformProperty { target: button; platform: "symbian"; name:
"foobar"; value: 1; }
PlatformProperty { target: button; platform: "symbian"; name:
"font.pixelSize"; value: 30; }
// listen for signals when platform is symbian
PlatformConnections { target: button; platform: "symbian";
onFooBarChanged: print(button.platform.foobar); }
}
===
So we could handle these 'ifdefs' in an more elegant way, providing a
portable source code.
Accessing these properties directly would result in a non-portable or
a non-declarative source code. Like the following:
===
Button {
platform.color: "red"
platform.foobar: 4 // this will crash on meego, since foobar does not exist
onFooBarChanged: {
// this will crash on meego, since foobar does not exist
}
}
Button {
Component.onCompleted: {
if (qt_components_platform == "meego")
platform.color = "red";
else if (qt_components_platform == "symbian")
platform.foobar = 4;
// handle specific connections
}
}
===
A possible implementation for the PlatformProperty can be as follows:
===
import Qt 4.7
Binding {
id: binding
property string name
property string platform
property: "platform." + name
when: binding.platform == qt_components_platform // global context
}
===
However, I dislike the idea of having to handle multiple platforms in
the source code. IMO Nokia needs to converge to a single API for all
platforms Symbian, Meego and future ones.
Currently, if the difference between these APIs are small. I would
prefer to have a few redundant properties/signals in the common API,
instead of having to handle these extensions in my code.
Br,
Adriano
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