Re: [Development] Question about QtDeclarative Internals
Hi Ulf,
Thanks for the advice. I think I got it working.
Patch submitted on Gerrit:
https://codereview.qt-project.org/c/qt/qtdeclarative/+/345339
It includes documentation and a test, and it works with named imports (i.e.
import { version } from "info")
Mostly it was just storing the QJSValues as PersistentValues, then
converting them to StaticValues when needed.
There were some other things, like telling the engine to skip calling
loadModule in the ExecutionUnit if it's already been registered in
nativeModules.
It works for any QJSValue, but one thing that might make this feature more
useful in the future is exposing functions or methods as a QJSValue.
One way might just be to have a std::function constructor (for a lambda)
Another might be to have QJSValue act as an intermediary between an
imported function in JavaScript and a slot in a QObject. That might require
some internal changes though.
But that's a whole different discussion. For now, I hope this works.
Thanks for your advice,
Alex
On Thu, Apr 22, 2021 at 1:55 AM Ulf Hermann wrote:
> Hi Alex,
>
> the simplest way I can see here would not be a compilation unit. The
> compilation unit is only needed if you want to run JavaScript. The place
> where the imports of a script are saved is
> QV4::CompiledData::CompilationUnitBase::imports of the _importing_ unit.
> That's an array QV4::StaticValue*. Imports are always resolved
> statically when loading the script that does the import.
>
> You need a way to tell the engine "Hey, here is my implementation of
> foobar, use that when importing foobar in JavaScript". Then you can just
> provide a QV4::Value (that has been protected against garbage collection
> in some way) as that will fit the bill for the imports array.
>
> You might store those values as a hash of QUrl to QV4::PersistentValue
> in QV4::ExecutionEngine. Then you can query them in addition to the
> compilation units whenever something is imported. In a second step, the
> original modules hash may be changed to store some abstraction over both
> variations.
>
> This of course does involve some changes in the QML engine itself.
> However, better integration of C++ into JavaScript (as opposed to QML)
> has been on my list for a long time. This would be a welcome addition.
> Don't hesitate to ask me if you have further questions. You can also
> find me on freenode IRC in the #qt-v4vm channel.
>
> best regards,
> Ulf
>
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Re: [Development] Question about QtDeclarative Internals
Hi Alex, the simplest way I can see here would not be a compilation unit. The compilation unit is only needed if you want to run JavaScript. The place where the imports of a script are saved is QV4::CompiledData::CompilationUnitBase::imports of the _importing_ unit. That's an array QV4::StaticValue*. Imports are always resolved statically when loading the script that does the import. You need a way to tell the engine "Hey, here is my implementation of foobar, use that when importing foobar in JavaScript". Then you can just provide a QV4::Value (that has been protected against garbage collection in some way) as that will fit the bill for the imports array. You might store those values as a hash of QUrl to QV4::PersistentValue in QV4::ExecutionEngine. Then you can query them in addition to the compilation units whenever something is imported. In a second step, the original modules hash may be changed to store some abstraction over both variations. This of course does involve some changes in the QML engine itself. However, better integration of C++ into JavaScript (as opposed to QML) has been on my list for a long time. This would be a welcome addition. Don't hesitate to ask me if you have further questions. You can also find me on freenode IRC in the #qt-v4vm channel. best regards, Ulf ___ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
Re: [Development] Question about QtDeclarative Internals
Hello Fabian,
Thanks for replying.
The QJSValue represents any basic JS type that could be exported from a
regular module.
For example:
export const MAGIC = 6;
export default {
name: "Qt6",
version: "6.1.3"
}
In C++:
QJSValue magic(6);
QJSValue name("Qt6");
QJSValue version("6.1.3");
QJSValue obj = myEngine.newObject();
obj.setProperty("name", name);
obj.setProperty("version", version);
myEngine.registerModule("magic", magic);
myEngine.registerModule("qt_info", obj);
Then in JS:
import MAGIC from "magic";
import { version } from "qt_info";
Basically, it's like CreateSyntheticModule from V8.
I think something like this could be useful for applications using JS as a
scripting language.
There might be other ways to do what I need than converting QJSValue to an
ExecutableCompilationUnit;
I just thought this might be the most straightforward.
Thanks,
Alex
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Re: [Development] Question about QtDeclarative Internals
Hi, there is certainly no straightforward way from QV4::Value to ExecutableCompilationUnit, especially considering that the Value can be anything, from a primitive like bool or undefined to basically arbitrary objects managed on the engine's heap. Could you expand a bit more how exactly you envision registerModule to work? What is your QJSValue supposed to contain: - A string with the JS code of the module? - An URL? - A C++ object which ought to provide methods that can then be used in the JS engine? Regards, Fabian -- Fabian Kosmale Software Engineer The Qt Company GmbH Erich-Thilo-Str. 10 D-12489 Berlin fabian.kosm...@qt.io +49 1638686070 http://qt.io Geschäftsführer: Mika Pälsi, Juha Varelius, Jouni Lintunen Sitz der Gesellschaft: Berlin Registergericht: Amtsgericht Charlottenburg, HRB 144331 B -- Von: Development im Auftrag von Alex Shaw Gesendet: Mittwoch, 21. April 2021 16:18 An: development@qt-project.org Betreff: [Development] Question about QtDeclarative Internals Hello, In QtDeclarative, can a QV4::ReturnedValue or a QV4::Value be converted into an ExecutableCompilationUnit? I'm trying to work on a patch for QJSEngine to allow importing modules from C++ (similar to Node.js: import fs from "fs") The planned method is something along the lines of: void QJSEngine::registerModule(const QString , const QJSValue ) I can see that behind the scenes, loadModule compiles a URL to an ExecutableCompilationUnit, then saves it to a list of modules for future lookup. I thought the easiest way to do what I need is to convert a QJSValue to an internal QV4::Value, and from there into an ExecutableCompilationUnit. Is there any way of doing that? Thanks. ___ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
Re: [Development] Question about QtDeclarative Internals
> Hello, > > In QtDeclarative, can a QV4::ReturnedValue or a QV4::Value be converted into > an ExecutableCompilationUnit? > > I'm trying to work on a patch for QJSEngine to allow importing modules from > C++ (similar to Node.js: import fs from "fs") > The planned method is something along the lines of: > void QJSEngine::registerModule(const QString , const QJSValue > ) > > I can see that behind the scenes, loadModule compiles a URL to an > ExecutableCompilationUnit, then saves it to a list of modules for future > lookup. > I thought the easiest way to do what I need is to convert a QJSValue to an > internal QV4::Value, and from there into an ExecutableCompilationUnit. > Is there any way of doing that? This may not be what you asked for, but having done NodeJS, I would probably just recommend importing a Qt QObject as a Singleton to expose the functions under the fa import. See qmlRegisterSingletonType(). import org.mine.fs 1.0 ... var file = fs.openFileSync(...); ... ___ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
[Development] Question about QtDeclarative Internals
Hello, In QtDeclarative, can a QV4::ReturnedValue or a QV4::Value be converted into an ExecutableCompilationUnit? I'm trying to work on a patch for QJSEngine to allow importing modules from C++ (similar to Node.js: import fs from "fs") The planned method is something along the lines of: void QJSEngine::registerModule(const QString , const QJSValue ) I can see that behind the scenes, loadModule compiles a URL to an ExecutableCompilationUnit, then saves it to a list of modules for future lookup. I thought the easiest way to do what I need is to convert a QJSValue to an internal QV4::Value, and from there into an ExecutableCompilationUnit. Is there any way of doing that? Thanks. ___ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
