[Development] QtQml Loader API

Martin Jones martin.jones at qinetic.com.au
Tue Dec 11 05:15:02 CET 2012

On Tue, Dec 11, 2012 at 1:32 PM, Alan Alpert <416365416c at gmail.com> wrote:
> Finally Qt 5 brings better QtQml and QtQuick separation! Better, not
> perfect. The main things I've heard are missing is dynamic
> instantiation of non-Items. What I propose is a new element for the
> QtQml module which provides that functionality. Note that while some
> people have suggested that Repeater and Loader could just accept
> non-Item delegates, they both provide visual item related
> functionality. For example, Repeater assigns items to the
> Item::children property and Loader has visual sizing behavior. We
> can't just disable that functionality if the delegate is non-visual,
> because (aside from being a terrible API) we want the functionality in
> the QtQml import.

It should be noted that since e8206bf6ab6ef62b5dd24bf002aa56edecbcec97
Loader can instantiate non-Item types, so you do have some of this
functionality available now, though, as you've noted above not in the
right place.

> So lets start thinking about the potential API for
> this functionality. Here's my first thoughts.
> Prototype API of the Instantiator element:
> QtObject {
>     property bool active: true
> property
>     property model model: 1
>     property Component delegate //Note Component is in the QtQml module
>     property QtObject object //Convenience for objects[0]
>     property list<QtObject> objects
> }
> The big question about this API is whether it's better served with two
> elements. I'm thinking it could be done with just a single element,
> but maybe it's worth duplicating it to have a Loader-like one (with
> just object) and a Repeater-like one (with just objects). Note that
> Repeater and Loader have some GUI functionality that is different for
> groups versus single objects - Repeater visually reparents all
> children (only really useful for groups) and Loader controls the size
> of its one object (only really feasible for one). Is it worth making
> two separate types?

I definitely think it's worth two types.  The status property,
onLoaded handler, etc. of Loader are quite useful, but don't make
sense for a multi-object loader.


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