Re: [Qt-jambi-interest] Request for contributors
Is there any willing to contribute? We should try to compile a list of what has to be done to get the first community release on Qt 4.6 going. On the top of my head: 1. Get the development packages up and running on the main Linux distros in addition to a tar.gz archive. 2. Get a Windows 7 release packaged. 3. Hopefully get someone on with a Mac to contribute with a release here. 4. Get the javadoc working again (I've managed to compile it, but it's lot of stuff missing which is found in the Qt doc). 5. Get the examples working and bundle them in the various packages. 6. Get in control of the Qt Jambi generator. Hi! I would like to join in the fun. I can help contribute to a Mac release. My particular interest is in making the Generator work better, so it can be run independently. Though it sounds like Francis may have already started working on that, which is great. I'm on vacation at the moment, so things are a little crazy but as a start, I'll try to take a look at what is involved in getting a Mac release going. -Adam Batkin ___ Qt-jambi-interest mailing list Qt-jambi-interest@trolltech.com http://lists.trolltech.com/mailman/listinfo/qt-jambi-interest
Re: [Qt-jambi-interest] Jambi and JNI Integration
Initializing my QApplication first does in fact solve the problem. I'm not sure how I missed that (*smacks forehead*). Mostly because I was doing this in a 4-line test harness and not an actual program (which would of course have initialized QT since using QT Jambi is the whole point of this exercise!) You mentioned being able to move some code around to fix this particular issue but that wouldn't be a general fix; I would say that even better (if possible) would be to warn that you have to initialize QT first. I mention this because some classes do in fact print warnings if you try to use them without initializing QT first (for example when I was testing and I created an empty QPixmap, it yelled at me). In other words, what I did was wrong, but it would have been helpful to get a warning or something (since JVM crashes aren't the easiest things to debug) Anyway, thanks for the help! -Adam Batkin Eskil Abrahamsen Blomfeldt wrote: Adam Batkin wrote: Anyway, I've now set out to write my own JNI code to do what I want, instead of using the Jambi Generator. Everything was working nicely until trying to transfer a QImage from C++ to a Java/Jambi QImage. Back in February, Gunnar suggested stealing some logic from the generated Jambi code, in particular QPixmap::toImage(): jobject jimg = qtjambi_from_object(env, image, QImage, com/trolltech/qt/gui/, true); This works -- almost. I get back a valid Java QImage object (System.err.println(image) prints something like [EMAIL PROTECTED]) but when I try to do anything with it (like call image.width()), the JVM crashes. Hi, Adam. Has Qt Jambi been properly initialized at this point? I.e. you need to initialize each of the libraries you use before they can be used, otherwise Qt Jambi won't know e.g. that it has to copy the QImage into a new object before linking it into a Java object, and you will get a Java object with a pointer into the stack. The initialization of Qt Jambi libraries is done the first time a class from the library is loaded by the virtual machine. In your case, I think you are calling the conversion code before loading any Jambi GUI classes. The conversion code itself will resolve and load the QImage class, thus initializing the GUI library, but unfortunately this is too late for the first conversion, and the first Java object you retrieve will contain a pointer to the object you allocated on stack. This is why you can fix the problem by manually loading the class using the resolveClass() call, or by calling another method which causes the library to be initialized. We can easily fix this particular problem by moving some code around, and I'll make a suggestion to do so. However, I'm not convinced that we'll be able to fix all related issues, so I recommend you initialize the library prior to using Qt Jambi. For instance, we don't support having Qt Jambi application that have not called QApplication.initialize() or QCoreApplication.initialize() (the former in your case.) If you call QApplication.initialize() in the beginning of your application, this should cause the GUI library to be initialized. -- Eskil ___ Qt-jambi-interest mailing list Qt-jambi-interest@trolltech.com http://lists.trolltech.com/mailman/listinfo/qt-jambi-interest
[Qt-jambi-interest] Jambi and JNI Integration
Hi, I had posted a while back about wrapping the Poppler PDF library using QT Jambi, so that it could be used from Java. Although Poppler uses C++ Namespaces, I wrapped the 3 or 4 functions that I wanted in my own class, used the Jambi Generator and everything was great. At the time, it was mentioned that better Namespace support was coming with 4.4 so I figured I would wait until then to properly wrap the entire library (without having to also write my own C++ classes to wrap ever Poppler class that I wanted). Anyway, I've now set out to write my own JNI code to do what I want, instead of using the Jambi Generator. Everything was working nicely until trying to transfer a QImage from C++ to a Java/Jambi QImage. Back in February, Gunnar suggested stealing some logic from the generated Jambi code, in particular QPixmap::toImage(): jobject jimg = qtjambi_from_object(env, image, QImage, com/trolltech/qt/gui/, true); This works -- almost. I get back a valid Java QImage object (System.err.println(image) prints something like [EMAIL PROTECTED]) but when I try to do anything with it (like call image.width()), the JVM crashes. Now, the image object (QImage) that I'm getting back is on the stack (hence the address-of ). If I make a copy of it on the heap (QImage *copy = new QImage(image)) and then pass that copy pointer directly to the qtjambi_from_object function (i.e. no address-of operator since it is naturally a pointer) then it doesn't crash -- so long as I don't delete the copy pointer (which makes that a big memory leak). (creating a copy, not deleting it, but using the original image in qtjambi_from_object DOES crash the JVM (weird)). Something else that is weird (though this may be a red-herring, i.e. luck) if I construct more than 1 QImage (in Java, i.e. QImage i1 = page.renderToImage(); QImage i2 = page.renderToImage();) calling i1.width() crashes the JVM but i2.width() does not! (i1 being the first QImage created this way) In fact, just the line new QPixmap().toImage() seems to prevent a crash. Through some trial and error, I tried inlining a bunch of the code from qtjambi_from_object and it seems that just calling the following one line before calling qtjambi_from_object prevents a crash: resolveClass(env, className, packageName); Thoughts? Thanks, -Adam Batkin ___ Qt-jambi-interest mailing list Qt-jambi-interest@trolltech.com http://lists.trolltech.com/mailman/listinfo/qt-jambi-interest
