[Development] qqmlengine/qqmlimport access

[Simon Hausmann]

On Tuesday, June 02, 2015 03:44:59 PM rpzrpzrpz at gmail.com wrote:
> On 5/29/2015 9:53 AM, mark diener wrote:
> > Hello dev list:
> > 
> > Qt 5.4.1.
> > 
> > At the top of qqmlimport_p.h, it discusses how it is NOT part of the QT
> > API and subject to change.
> > 
> > In qqmlengine.h, there is addImportPath( ) to allow qqmlimport to
> > resolve types using a module/qmldir file.
> > 
> > But ByteArray derived components have no equivalent treatment:
> > 
> > 
> > QByteArray  gbytes("import  QtQuick  2.4\n  Rectangle  { 
> > objectName:\"myRecto\"\n  color:  \"blue\"  }");
> > 
> > QQmlComponent  gcomponent(&gengine)  ;
> > 
> > gcomponent.setData(gbytes,QUrl("Myrectangle.qml"));
> > 
> > 
> > How to add the QQmlComponent in the QQmlEngine import database so that
> > QQmlImports::addImplicitImport( ) can resolve component type?
> > 
> > There is no new C++ type here, just a new component defined in QML, so
> > qmlRegisterType<C++type>(bla,bla,bla) is a fail.
> > 
> > Or maybe there is a non-qmldir file method to use importExtension with
> > QQmlComponent?  (qmldir file alternative)
> > 
> > Does QQmlEngine have a public access way to achieve the following:
> > 
> > QQmlEngine::addImportComponent(QString gname,QQmlComponent& gcomponent) ;
> > QQmlEngine::removeImportComponent(QString gname) ;
> > 
> > In QML, I could either have an importExtension()  OR an implicitImport()
> > in qqmlimports.
> > 
> > Thanks,
> > 
> > Mark
> 
> Simon:
> 
> I think the absence of responses from the dev list indicates I have
> touched on a topic dead zone that resides in your area as QML/core
> maintainer.
> 
>  From what I can tell, the QML component cache and import mechanisms
> lack any public access members for direct query,loading, and removal.

Yes.
 
> There are the blunt force methods of QQmlEngine->clearComponentCache()
> and QQmlEngine->trimComponentCache().
> 
> Maybe after the 5.5 release, I would like to explore adding public
> access member functions to QQmlEngine.h/cpp:
> 
> int QQmlEngine::loadComponent(QQmlComponent& component, QString&
> importQmlName);
> 
> int QQmlEngine::clearComponent(QString& importQmlName);
> 
> bool QQmlEngine::isComponentLoaded(QString& component);
> 
> The biggest concern I see is the caveat warnings given by qqmlimport.h

I'm wondering what the specific use-cases are. More specifically what criteria 
would be used to call these functions?

If you'd like to "pre-load" components, then I agree that we could have 
dedicated API for this, although you can already do this today by creating an 
async QQmlComponent and just not call create() on it.
 
> Another concern I have is the Render Thread issues VS Gui thread issues.
> 
> What group of devs is current this?
> 
> Does that group even talk to strangers?

Hehe.


Simon