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• How to force calling of QWidget::paintEvent() when its hovered by other window?

  - by Pie_Jesu

  Hi there. I have occured a problem: I'm writing a widget, which displays current date's day number. It's like a button, but it's not derived from QPushButton class. Just from QWidget. So I reimplemented enterEvent(), leaveEvent(), mousePressEvent(), mouseReleaseEvent(). I call update() inside these methods and widget has realistic button behavior (paintEvent() is reimplemented too). But when I change system date and hover that widget with other window, my widget doesn't calls paintEvent() and displays old date. Only when I place mouse over it, widget repaints it's contents. I guess there is an option, which paints old contents on hover event to avoid unnecessary paint events. But I need to disable it. Tried to set many attributes (Qt::WidgetAttribute enum). But it doesn't helps. Please, help me (and sorry for my bad english).

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• Large number of simultaneous long-running operations in Qt

  - by Hostile Fork

  I have some long-running operations that number in the hundreds. At the moment they are each on their own thread. My main goal in using threads is not to speed these operations up. The more important thing in this case is that they appear to run simultaneously. I'm aware of cooperative multitasking and fibers. However, I'm trying to avoid anything that would require touching the code in the operations, e.g. peppering them with things like yieldToScheduler(). I also don't want to prescribe that these routines be stylized to be coded to emit queues of bite-sized task items...I want to treat them as black boxes. For the moment I can live with these downsides: Maximum # of threads tend to be O(1000) Cost per thread is O(1MB) To address the bad cache performance due to context-switches, I did have the idea of a timer which would juggle the priorities such that only idealThreadCount() threads were ever at Normal priority, with all the rest set to Idle. This would let me widen the timeslices, which would mean fewer context switches and still be okay for my purposes. Question #1: Is that a good idea at all? One certain downside is it won't work on Linux (docs say no QThread::setPriority() there). Question #2: Any other ideas or approaches? Is QtConcurrent thinking about this scenario? (Some related reading: how-many-threads-does-it-take-to-make-them-a-bad-choice, many-threads-or-as-few-threads-as-possible, maximum-number-of-threads-per-process-in-linux)

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• Qt, no such slot error

  - by Martin Beckett

  I'm having a strange problem with slots in Qt4.6 I have a tree control that I am trying to fire an event back to the mainwindow to edit something. I have boiled it down to this minimal example: class MainWindow : public QMainWindow { Q_OBJECT public: MainWindow(int argc, char **argv ); private Q_SLOTS: void about() {QMessageBox::about(this, "about","about"); } // Just the defaul about box void doEditFace() {QMessageBox::about(this, "test","doEditFace"); } // pretty identical .... } class TreeModel : public QAbstractItemModel { Q_OBJECT Q_SIGNALS: void editFace(); ... } In my Mainwindow() I have connect(treeModel, SIGNAL(editFace()), this, SLOT(about())); // returns true connect(treeModel, SIGNAL(editFace()), this, SLOT(doEditFace())); // returns false When I run it the second line gives a warning. Object::connect: No such slot MainWindow::doEditFace() in \src\mainwindow.cpp:588 As far as I can see the doEditFace() is in the moc_ qmeta class perfectly correctly. And the edit event fires and pops up the about box. The order doesn't matterm if I connect the about box second it still works but my slot doesnt! vS2008 windowsXP qt4.6.2

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• Disable text selection in QT/WebKit GUI

  - by Adal

  I'm checking if it would be possible to implement a GUI using HTML through PyQT and WebKit. One of the problem is that using the mouse you can select the text making up the interface. Can this behaviour be disabled? Also, the mouse pointer changes to an insertion caret while over the selectable text. I would like to disable this, without disabling the hand mouse pointer which appears when over a clickable link.

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• Phonon::VideoWidget not working in Qt 4.4

  - by user249490

  Hi, I have Phonon::VideoWidget, Phonon::MediaObject and Phonon::MediaSource, all initialized as below. videoWidget=new Phonon::VideoWidget(this); mediaVideoObject=new Phonon::MediaObject(this); Phonon::createPath(mediaVideoObject, videoWidget); Phonon::MediaSource mediaSource= Phonon::MediaSource("D:\\file.avi"); mediaVideoObject->setCurrentSource(mediaSource); and all connections laid for Play, Pause, Next, Previous. It is working for few videos while for some other it is throwing IDispatch error #24 (0x80040218) and error type as Fatal. I am using Qt4.4 in windows XP and has backend support as well. I have to play those videos which are throwing the above mentioned error. What might be the reason and how i can overcome the error?

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• How to access Postgresql using QT in Windows

  - by dummystories

  Hi to all, I am developing an application using QtRuby and postgresql. I sucessfully developed and running sucessfully in Linux. Now i want to run the same application in windows. But i am failing to connect to database(Postgresql). I am getting the following errors: QSqlDatabase: QPSQL driver not loaded QSqlDatabase: available drivers: QSQLITE QODBC3 QODBC Can any one help how to resolve my problem. I am waiting for your replies. Regards, Narasimha Raju.Naidu

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• QT intellisense question

  - by uzay95

  in this code: #include <QApplication> #include <QPushButton> int main(int argc,char *argv[]) { QApplication app(argc,argv); QPushButton *button = new QPushButton("Button Text"); QObject::connect(button,SIGNAL(clicked()),&app,SLOT(quit())); button->show(); return app.exec(); } intellisense is appearing when the cursor is in SIGNAL parenthesis to write button event. But it doesn't appear in SLOT parenthesis to write app method ? is it related with & character in front of app ?

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• QT QFileDialog how to hide hidden/backup folders (".folder")

  - by Alberto Toglia

  Basically when browsing folders inside a QFileDialog I find very annoying to have everything bloated with hidden or backup folders (don't know how to call them really); specially on home. Is there a way to prevent these type of folders from showing by default on a QFileDialog? I'm using Qt4.6 and getOpenFileName. P.D.: I'm starting to think this might be an ubuntu thing...?

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• layer structure of Qt

  - by Ann

  I want to know the different layers included in Qt4.6,for knowing deep about the system design.

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• How to display a Dialog on window created using XCreateWindow in QT 4.5.2

  - by Ummar

  I am doing work on project. In which I have developed a full size screen displaying images using XCreateWindow. Now I want to display a dialog on this screen. I have created a QDialog it does'nt show on the full size screen but it is displayed on screen when it is not full size. Any Help. My code for creating screen and dialogbox is as follows XSetWindowAttributes attribs; XClassHint *classhints; XSizeHints *sizehints; int wndwidth, wndheight; long input_mask, ic_input_mask; XEvent xevent; wndwidth = fullscreen ? WidthOfScreen(screen) : width; wndheight = fullscreen ? HeightOfScreen(screen) : height; attribs.background_pixel = BlackPixelOfScreen(screen); attribs.backing_store = ownbackstore ? NotUseful : Always; attribs.override_redirect = fullscreen; wnd = XCreateWindow(display, RootWindowOfScreen(screen), 0, 0, wndwidth, wndheight, 0, CopyFromParent, InputOutput, CopyFromParent, CWBackPixel | CWBackingStore | CWOverrideRedirect, &attribs); XRaiseWindow(display, wnd); //QDialog I want to show on wnd(XCreateWindow) ToolbarDialog *objToolbarDialog= new ToolbarDialog(); objToolbarDialog->setVisible(true); objToolbarDialog->showNormal();

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• Qt gstreamer problem

  - by ZolaKt

  Ptterb can you post your full code please? I copied your code. Added fvidscale_cap to pipeline, with: self.player.add(self.source, self.scaler, self.fvidscale_cap, self.sink) gst.element_link_many(self.source,self.scaler, self.fvidscale_cap, self.sink) From the main program I create a new QWidget, and pass its winId() to Vid constructor. The widget start loading, but crashes. The output says: should be playing Segmentation fault

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• Hook key & key combinations from keyboard with Qt 4.6

  - by Viet

  Let's say I have a window-less application which has only an icon on the Taskbar (Windows, Mac OS X & Linux). I want it to capture some key & key combinations, let's say Right Control + Right Shift. Upon keying in correct, combination, it will do something, say take screenshot. I can do window-less app, icon on the Taskbar and screen capture but I don't know how to monitor keyboard globally for key combinations. Please kindly advise. Any help or hint is greatly appreciated! Thanks in advance!

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• Calculix Data Visualiser using QT

  - by Ann

  I am doing a project on Calculix Data Visualiser. It is a civil based project. I need to show the structure of beams before applying force and the structure after the force is applied. I need to change the color of the beams to RED where more force is applied. But i am just able to change the color for lines and not for the phase as a whole. SO pls help me out.

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• Calculix Data Visualiser using QT,zooming

  - by Ann

  how could i zoom-in and zoom-out the output image.it should be user friendly,means using push button.Please send me a code for that.

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• Converting QXmlItem to QtDomElement or similar?

  - by EightyEight

  Hello everyone. I'm parsing a fairly complicated XML file of the following structure: <root> ... ... <item> <subitem id="1"/> <text> text1 </text> </item> <item> <subitem id="2"/> <text> text2 </text> </item> ... <item> ... </item> ...</root> It's pretty crude but you get my drift I hope. I'm primarily interested in "item" nodes. So I wrote the following code (directly out of the Qt's online manual): QXmlQuery query; query.setQuery("//item/"); QXmlResultItems result; query.evaluateTo(&result); QXmlItem item(result.next()); while (!item.isNull()) { if (item.isNode()) { // WHAT DO I DO NOW? } item = result.next(); } Now, QXmlItem appears to represent two concepts, a literal value (like a string) or a Node, (which is what item.isNode() is doing). Unfortunately, I can't grasp how to convert the QXmlItem to something that will query-able again. In particular from the example above I'd like to grab the "id" attribute, and the text element. Can I do this using the XQuery approach, or am I way off base here? Any advice? Thanks!

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• QWebView not loading external resources

  - by Nick

  Hi. I'm working on a kiosk web browser using Qt and PyQt4. QWebView seems to work quite well except for one quirk. If a URL fails to load for any reason, I want to redirect the user to a custom error page. I've done this using the loadFinished() signal to check the result, and change the URL to the custom page if necessary using QWebView.load(). However, any page I attempt to load here fails to pull in external resources like CSS or images. Using QWebView.load() to set the initial page at startup seems to work fine, and clicking any link on the custom error page will result in the destination page loading fine. It's just the error page that doesn't work. I'm really not sure where to go next. I've included the source for an app that will replicate the problem below. It takes a URL as a command line argument - a valid URL will display correctly, a bad URL (eg. DNS resolution fails) will redirect to Google, but with the logo missing. import sys from PyQt4 import QtGui, QtCore, QtWebKit class MyWebView(QtWebKit.QWebView): def __init__(self, parent=None): QtWebKit.QWebView.__init__(self, parent) self.resize(800, 600) self.load(QtCore.QUrl(sys.argv[1])) self.connect(self, QtCore.SIGNAL('loadFinished(bool)'), self.checkLoadResult) def checkLoadResult(self, result): if (result == False): self.load(QtCore.QUrl('http://google.com')) app = QtGui.QApplication(sys.argv) main = MyWebView() main.show() sys.exit(app.exec_()) If anyone could offer some advice it would be greatly appreciated.

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• Shift count negative or too big error - correct solution?

  - by PeterK

  I have the following function for reading a big-endian quadword (in a abstract base file I/O class): unsigned long long CGenFile::readBEq(){ unsigned long long qT = 0; qT |= readb() << 56; qT |= readb() << 48; qT |= readb() << 40; qT |= readb() << 32; qT |= readb() << 24; qT |= readb() << 16; qT |= readb() << 8; qT |= readb() << 0; return qT; } The readb() functions reads a BYTE. Here are the typedefs used: typedef unsigned char BYTE; typedef unsigned short WORD; typedef unsigned long DWORD; The thing is that i get 4 compiler warnings on the first four lines with the shift operation: warning C4293: '<<' : shift count negative or too big, undefined behavior I understand why this warning occurs, but i can't seem to figure out how to get rid of it correctly. I could do something like: qT |= (unsigned long long)readb() << 56; This removes the warning, but isn't there any other problem, will the BYTE be correctly extended all the time? Maybe i'm just thinking about it too much and the solution is that simple. Can you guys help me out here? Thanks.

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• Losing 'post' requests sent to Pylons paster server

  - by Philip McDermott

  I'm sending post requests to a Pylons server (served by paster serve), and if I send them with any frequency many don't arrive at the server. One at a time is ok, but if I fire off a few (or more) within seconds, only a small number get dealt with. If I send with no post data, or with get, it works fine, but putting just one character of data in the post fields causes massive losses. For example, sending 200, 2 will come back. Sending 100 more slowly, 10 will come back. I'm making the requests form inside a Qt application. Tis will work ok (no data): QString postFields = "" QNetworkRequest request(QUrl("http://server.com/endpoint")); QNetworkReply *reply = networkAccessManager-post(request, postFields.toAscii()); And this will result in only a fraction of the requests being dealt with: QString postFields = "" QNetworkRequest request(QUrl("http://server.com/endpoint")); QNetworkReply *reply = networkAccessManager-post(request, postFields.toAscii()); I've played around with turning on use_threadpool, and other options (threadpool_workers, threadpool_max_requests = 300), of which some combinations can alter the results slightly (best case 10 responses in 200). If I send similar requests to other (non paster) servers, the replies come back ok, so I'm almost certain its'a paster serve config issue. Any help or advice greatly appreciated. Thanks Philip

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• Emulating a web browser

  - by Sean

  Hello, we are tasked with basically emulating a browser to fetch webpages, looking to automate tests on different web pages. This will be used for (ideally) console-ish applications that run in the background and generate reports. We tried going with .NET and the WatiN library, but it was built on a Marshalled IE, and so it lacked many features that we hacked in with calls to unmanaged native code, but at the end of the day IE is not thread safe nor process safe, and many of the needed features could only be implemented by changing registry values and it was just terribly unflexible. Proxy support JavaScript support- we have to be able to parse the actual DOM after any javascript has executed (and hopefully an event is raised to handle any ajax calls) Ability to save entire contents of page including images FROM THE loaded page's CACHE to a separate location ability to clear cookies/cache, get the cookies/cache, etc. Ability to set headers and alter post data for any browser call And for the love of drogs, an API that isn't completely cryptic Languages acceptable C++, C#, Python, anything that can be a simple little console application that doesn't have a retarded syntax like Ruby. From my own research, and believe me I am terrible at google searches, I have heard good things about WebKit... would the Qt module QtWebKit handle all these features?

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• Finding a 3rd party QWidget with injected code & QWidget::find(hwnd)

  - by David Menard

  Hey, I have a Qt Dll wich I inject into a third-party Application using windows detours library: if(!DetourCreateProcessWithDll( Path, NULL, NULL, NULL, TRUE, CREATE_DEFAULT_ERROR_MODE | CREATE_SUSPENDED, NULL, NULL, &si, &pi, "C:\\Program Files\\Microsoft Research\\Detours Express 2.1\\bin\\detoured.dll", "C:\\Users\\Dave\\Documents\\Visual Studio 2008\\Projects\\XOR\\Debug\\XOR.dll", NULL)) and then I set a system-wide hook to intercept window creation: HHOOK h_hook = ::SetWindowsHookEx(WH_CBT, (HOOKPROC)CBTProc, Status::getInstance()->getXORInstance(), 0); Where XOR is my programs name, and Status::getInstance() is a Singleton where I keep globals. In my CBTProc callback, I want to intercept all windows that are QWidgets: HWND hwnd= FindWindow(L"QWidget", NULL); which works well, since I get a corresponding HWND (I checked with Spy++) Then, I want to get a pointer to the QWidget, so I can use its functions: QWidget* q = QWidget::find(hwnd); but here's the problem, the returned pointer is always 0. Am I not injecting my code into the process properly? Or am I not using QWidget::find() as I should? Thanks, Dave EDIT:If i change the QWidget::find() function to an exported function of my DLL, after setting the hooks (so I can set and catch a breakpoint), QWidgetPrivate::mapper is NULL.

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• Using custom coordinates with QGraphicsScene

  - by Rob

  I am experimenting with a WYSIWYG editor that allows a user to draw shapes on a page and the Qt graphics scene support seems perfect for this. However, instead of working in pixels I want all my QGraphicsItem objects to work in tenths of a millimetre but I don't know how to achieve this. For example: // Create a scene that is the size if an A4 page (2100 = 21cm, 2970 = 29.7cm) QGraphicsScene* scene = new QGraphicsScene(0, 0, 2100, 2970); // Add a rectangle located 1cm across, 1cm down, 5cm wide and 2cm high QGraphicsItem* item = scene->addRect(100, 100, 500, 200); ... QGraphicsView* view = new QGraphicsView(scene); setCentralWidget(view); Now, when I display the scene above I want the shapes to appear at correct size for the screen DPI. Is this simply a case of using QGraphicsView::scale or do I have to do something more complicated? Note that if I was using a custom QWidget instead then I would use QPainter::setWindow and QPainter::setViewport to create a custom mapping mode but I can't see how to do this using the graphics scene support.

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• QTableWidget::itemAt() returns seemingly random items

  - by Jordan Milne

  I've just started using Qt, so please bear with me. When I use QTableWidget-getItemAt(), it returns a different item from if I used currentItemChanged and clicked the same item. I believe it's necessary to use itemAt() since I need to get the first column of whatever row was clicked. Some example code is below: MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow) { ui->setupUi(this); QList<QString> rowContents; rowContents << "Foo" << "Bar" << "Baz" << "Qux" << "Quux" << "Corge" << "Grault" << "Garply" << "Waldo" << "Fred"; for(int i =0; i < 10; ++i) { ui->tableTest->insertRow(i); ui->tableTest->setItem(i, 0, new QTableWidgetItem(rowContents[i])); ui->tableTest->setItem(i, 1, new QTableWidgetItem(QString::number(i))); } } //... void MainWindow::on_tableTest_currentItemChanged(QTableWidgetItem* current, QTableWidgetItem* previous) { ui->lblColumn->setText(QString::number(current->column())); ui->lblRow->setText(QString::number(current->row())); ui->lblCurrentItem->setText(current->text()); ui->lblCurrentCell->setText(ui->tableTest->itemAt(current->column(), current->row())->text()); } For the item at 1x9, lblCurrentItem displays "9" (as it should,) whereas lblCurrentCell displays "Quux". Am I doing something wrong?

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• How to set QNetworkReply properties to get correct NCBI pages?

  - by Claire Huang

  I try to get this following url using the downloadURL function: http://www.ncbi.nlm.nih.gov/nuccore/27884304 But the data is not as what we can see through the browser. Now I know it's because that I need to give the correct information such as browser, how can I know what kind of information I need to set, and how can I set it? (By setHeader function??) In VC++, we can use CInternetSession and CHttpConnection Object to get the correct information without setting any other detail information, is there any similar way in Qt or other cross-platform C++ network lib?? (Yes, I need the the cross-platform property.) QNetworkReply::NetworkError downloadURL(const QUrl &url, QByteArray &data) { QNetworkAccessManager manager; QNetworkRequest request(url); request.setHeader(QNetworkRequest::ContentTypeHeader ,"Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)"); QNetworkReply *reply = manager.get(request); QEventLoop loop; QObject::connect(reply, SIGNAL(finished()), &loop, SLOT(quit())); loop.exec(); QVariant statusCodeV = reply->attribute(QNetworkRequest::RedirectionTargetAttribute); QUrl redirectTo = statusCodeV.toUrl(); if (!redirectTo.isEmpty()) { if (redirectTo.host().isEmpty()) { const QByteArray newaddr = ("http://"+url.host()+redirectTo.encodedPath()).toAscii(); redirectTo.setEncodedUrl(newaddr); redirectTo.setHost(url.host()); } return (downloadURL(redirectTo, data)); } if (reply->error() != QNetworkReply::NoError) { return reply->error(); } data = reply->readAll(); delete reply; return QNetworkReply::NoError; }

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• How can I set QNetworkReply properties to get correct NCBI pages?

  - by Claire Huang

  I try to get this following url using the downloadURL function: http://www.ncbi.nlm.nih.gov/nuccore/27884304 But the data is not as what we can see through the browser. Now I know it's because that I need to give the correct information such as browser, how can I know what kind of information I need to set, and how can I set it? (By setHeader function??) In VC++, we can use CInternetSession and CHttpConnection Object to get the correct information without setting any other detail information, is there any similar way in Qt or other cross-platform C++ network lib?? (Yes, I need the the cross-platform property.) QNetworkReply::NetworkError downloadURL(const QUrl &url, QByteArray &data) { QNetworkAccessManager manager; QNetworkRequest request(url); request.setHeader(QNetworkRequest::ContentTypeHeader ,"Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)"); QNetworkReply *reply = manager.get(request); QEventLoop loop; QObject::connect(reply, SIGNAL(finished()), &loop, SLOT(quit())); loop.exec(); int direction; QVariant statusCodeV = reply->attribute(QNetworkRequest::RedirectionTargetAttribute); QUrl redirectTo = statusCodeV.toUrl(); if (!redirectTo.isEmpty()) { if (redirectTo.host().isEmpty()) { const QByteArray newaddr = ("http://"+url.host()+redirectTo.encodedPath()).toAscii(); redirectTo.setEncodedUrl(newaddr); redirectTo.setHost(url.host()); } return (downloadURL(redirectTo, data)); } if (reply->error() != QNetworkReply::NoError) { return reply->error(); } data = reply->readAll(); delete reply; return QNetworkReply::NoError; }

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• Serializing QGraphicsScene contents

  - by Rob

  I am using the Qt QGraphicsScene class, adding pre-defined items such as QGraphicsRectItem, QGraphicsLineItem, etc. and I want to serialize the scene contents to disk. However, the base QGraphicsItem class (that the other items I use derive from) doesn't support serialization so I need to roll my own code. The problem is that all access to these objects is via a base QGraphicsItem pointer, so the serialization code I have is horrible: QGraphicsScene* scene = new QGraphicsScene; scene->addRect(QRectF(0, 0, 100, 100)); scene->addLine(QLineF(0, 0, 100, 100)); ... QList<QGraphicsItem*> list = scene->items(); foreach (QGraphicsItem* item, items) { if (item->type() == QGraphicsRectItem::Type) { QGraphicsRectItem* rect = qgraphicsitem_cast<QGraphicsRectItem*>(item); // Access QGraphicsRectItem members here } else if (item->type() == QGraphicsLineItem::Type) { QGraphicsLineItem* line = qgraphicsitem_cast<QGraphicsLineItem*>(item); // Access QGraphicsLineItem members here } ... } This is not good code IMHO. So, instead I could create an ABC class like this: class Item { public: virtual void serialize(QDataStream& strm, int version) = 0; }; class Rect : public QGraphicsRectItem, public Item { public: void serialize(QDataStream& strm, int version) { // Serialize this object } ... }; I can then add Rect objects using QGraphicsScene::addItem(new Rect(,,,)); But this doesn't really help me as the following will crash: QList<QGraphicsItem*> list = scene->items(); foreach (QGraphicsItem* item, items) { Item* myitem = reinterpret_class<Item*>(item); myitem->serialize(...) // FAIL } Any way I can make this work?

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