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  • using sqlite database with qt

    - by Lakshan Perera
    here is my code, it dont seems enything wrong, QSqlDatabase db=QSqlDatabase::addDatabase("QSQLITE"); db.setDatabaseName("thedata.sqlite"); db.open(); QSqlQuery quary; quary.prepare("SELECT lastname FROM people where firstname='?' "); quary.bindValue(0,lineEdit->text()); bool x=quary.exec(); if(x){ //...... } else { QSqlError err; err=quary.lastError(); QMessageBox::about(this,"error",err.text() ); } when the program is working always it gives the error parameter count mismatch im using qt 4.8 and its own headers for using sqlite. I would be very thankful for eny advice, though I searched in google i see many posts in this issue but nothing helped me. thank you.

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  • Qt grabWindow coordinates shifted from GetCursorPos and GetWindowRect

    - by user1391
    In Qt, when I use the QPixmap::grabWindow(hwnd,x,y,h,w) function, the coordinates are shifted slightly, when compared to the coordinates using the windows api functions GetCursorPos and GetWindowRect. i.e. (0,0) from the point of view of GetCursorPos and GetWindowRect is at the very top left of the toolbar at the top of the window. But (0,0) for QPixmap::grabWindow is more "inside" (i.e. ignoring the window frame). How can I make these 2 coordinates consistent? Especially since the user might have different thicknesses for the window frame?

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  • QT: QPainter + GDI in the same widget?

    - by shoosh
    I'm trying to use the method described here to use a QPainter and GDI calls on the same widget. Unfortunately this tutorial seem to have been written on an earlier version of QT and now it does not work. I set the WA_PaintOnScreen flag and reimplement paintEngine() to return NULL. Then on the paintEvent() I create a QPainter, use it and then use some GDI calls to paint a bitmap. The GDI calls work fine but the QPainter does nothing. I get the following error on the console: QPainter::begin: Paint device returned engine == 0, type: 1 Is this simply not supported anymore? how can I do it? I've also tried creating an additional widget on top of the GDI-painting widget but that didn't go well as well since the top widget appears black and blocks the GDI widget.

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  • use qt and django to create desktop apps

    - by sandra
    Hi guys, I had this idea of creating desktop apps using django. The principe being: - Write the django app, and use something like cherrypy to serve it. - Write a Qt app in C++ to access it and this by using QtWebview (webkit) I'd like to "bundle" this in a single app. The lighter, the better :) So here are my questions and if you have better ideas and suggestions, please share them :) Is it possible to serve a django app with a c++ one? (a c++ server embedding python)? anyone did this before? Do you have some articles, blog posts? Thanks a lot!

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  • Windows Power State change event notification in Qt

    - by Surjya Narayana Padhi
    Hi Geeks, I developing a GUI in QT where I have to show the battery status icon. To get the system power status, I am using the windows API. But to show status anytime , do i need to use a thread to continuously read and display the power status? I am thinking of using event handler. But not sure how to implement. I am thinking that for just one status icon I will run a thread. Anybody has any better suggestion, please share.

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  • Implementing implicitly shared classes outside of Qt

    - by Timothy Baldridge
    I'm familiar with the way Qt uses D-pointers for managing data. How do I do this in my code? I tried this method: 1) move all data into a struct 2) add a QAtomicInt to the struct 3) implement a = operator and change my constructor/deconstructor to check-up on the reference count. The issue is, when I go to do a shallow copy of the object, I get an error about QObject declaring = as private. How then do I accomplish this? Here's an example of my copy operator: HttpRequest & HttpRequest::operator=(const HttpRequest &other) { other.d->ref.ref(); if (!d->ref.deref()) delete d; d = other.d; return *this; } Am I going about this the wrong way?

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  • QT Modeless dialog window dos'nt response to the move command

    - by user63898
    Hello all im using Modeless dialog in my application , and when i try to use the Modeless dialog move command from the MainWindow the Modeless dialog didint even show up,why ? (by the way if i remove the move command every thing works and i can see the dialog when called, i try to move it to the systray era. here somecode: M odelessDialog* ModelessDialog= new ModelessDialog(this); ModelessDialog->setModal(false); ModelessDialog->setAttribute(Qt::WA_DeleteOnClose); int topLeft_x = m_SystrayReq.topLeft().x(); int topLeft_y = m_SystrayReq.topLeft().y(); // the valus of x & y are just fine . ModelessDialog->move(topLeft_x,topLeft_y); ModelessDialog->show();

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  • Getting values from pro files in Qt

    - by user249490
    Hi, I am using Qt 4.5 in Windows XP. My pro file has the variable VERSION = 1.0. Now i need to read this variable and get its value (1.0) from the source code. So that I don't have to maintain another variable for version inside my source code. I just read from the pro file and update it. So that the value remains consistent all over my project. Is it possible? Any pointers regarding this are welcome..

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  • Qt: default value of variable in class

    - by Martin
    When creating my own class in Qt I would like my variables in the class to have a standard/default value if I haven't set them to anything. It would be perfect if this was possible to set in the h-file so I don't have to do it in each instance method of my class. You can see what I want to do in the code below. In the example myBool would have the value of false and myInt the value of 0 when the object have been created. Is this possible at all? In myclass.h: class MyClass { Q_OBJECT public: MyClass(); ~MyClass(); bool myBool = false; //I want to set myBool and myInt to a default/standard value int myInt = 0; };

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  • Qt and finding partial matches in a QList

    - by ExpatEgghead
    I have a struct viz: struct NameKey { std::string fullName; std::string probeName; std::string format; std::string source; } which are held in a QList: QList<NameKey> keyList; what I need to do is find an occurence in keyList of a partial match where the search is for a NameKey that only has two members filled. All the keyList entries are full NameKey's. My current implementation is , well, boring in the extreme with too many if's and conditions. So, If I have a DataKey with a fullName and a format I need to find all the occurences in keyList which match. Any useful Qt/boost things available?

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  • Qt layout problem.

    - by Lukasz Lew
    I have a following Qt code: QVBoxLayout* box = new QVBoxLayout; label = new QLabel(); // will be set later dynamically box->addWidget (label); Text in label will be set later. The problem is that when label resizes, it resizes QVBoxLayout, and it resizes other neighboring widgets. I don't want to make a label or layout fixed width. Because I want them to resize with a whole window. Is it possible to tell a widget to take all the place that it has in a layout, but not more?

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  • Qt Creator Debugging

    - by CJ
    I'm using QT Creator on 3 platforms to create platform independent software. However, I'm getting a segmentation fault with the exact same code in Windows only. That doesn't sound so bad because I can use the debugger. Except, no matter how many breakpoints I set or where I set them, they are ignored by the debugger. I am 100% sure that my control flow is going through the breakpoint but not breaking the flow. Any thoughts? How can that happen?

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  • Qt/C++ regular expression library with unicode property support

    - by Dave
    I'm converting an application from the .Net framework to Qt using C++. The application makes extensive use of regular expression unicode properties, i.e. \p{L}, \p{M}, etc. I've just discovered that the QRegExp class lacks support for this among other things (lookbehinds, etc.) Can anyone recommend a C++ regular expression library that: Supports unicode properties Is unicode-aware in other respects (i.e. \w matches more than ASCII word characters) As a bonus, supports lookbehinds. Please don't point me to the wikipedia article; I don't trust it. That article says that QRegExp supports unicode properties. Unless I'm really doing something wrong, it doesn't. I'm looking for someone actually using unicode properties with a regex library in a project.

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  • Analog of Java Form Layout in Qt

    - by Narek
    Once I have programmed GUI with Java and have used Form Layouts. Form layout (if I am not mistaken that is from SWT library) made possible to give right, left, top and bottom adges of any GUI element (widget) with respect to other widgets in the same widget (parent widget) or with respect to the adges of parent widget. So it was possible to control the future of widgets that are inside of another one, when that "another widget" is being resized. In Qt I have find the QFormLayout which is similar to Java one, but seems I can't handle with widgets as flexible in terms of relative positioning, as it was with Java's Form Layout. So are there any other means to give a widget position with respect to the others (without overloading resizeEvent function) as that was in Java? Thanks.

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  • Qt almost same main menu entries

    - by user1671710
    I'm using c++ Qt library and I want to do something which would do : connect(actionB11, SIGNAL(triggered()), this, SLOT(SetSomething(1, 1))); connect(actionB12, SIGNAL(triggered()), this, SLOT(SetSomething(1, 2))); connect(actionB21, SIGNAL(triggered()), this, SLOT(SetSomething(2, 1))); connect(actionB22, SIGNAL(triggered()), this, SLOT(SetSomething(2, 2))); The code above doesnt work because SIGNAL function has to have same number and argument types as SLOT function. Does exist a way how to do it? I dont want to have about 20 function as SetSomething11, SetSomething12 calling SetSomething(1, 1) etc.

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  • QT: trouble with qobject_cast

    - by weevilo
    I have derived QGraphicsItem and QGraphicsScene classes. I want the items to be able to call scene() and get a derviedGraphicsItem * instead of a QGraphicsItem *, so I reimplemented QGraphicsScene::itemAt to return a derived pointer. DerivedItem* DerivedScene::itemAt( const QPointF &position, const QTransform &dt ) const { return qobject_cast< DerivedItem * >( QGraphicsScene::itemAt(position, dt) ); } I get the following error (Qt 4.6, GCC 4.4.3 on Ubuntut 10.4) scene.cpp: In member function ‘DerivedItem* DerivedScene::itemAt(qreal, qreal, const QTransform&) const’: scene.cpp:28: error: no matching function for call to ‘qobject_cast(QGraphicsItem*)’ I then noticed QGraphicsItem doesn't inherit QObject, so I made my derived QGraphicsItem class have multiple inheritance from QObject and QGraphicsItem, and after adding the Q_OBJECT macro and rebuilding the project I get the same error. Am I going about this the wrong way? I know it's supposed to be bad design to try to cast a parent class as a child, but in this case it seems like what I want, since my derived item class has new functionality and its objects need a way to call that new functionality on items around themselves, and asking the items scene object with itemAt() seems like the best way - but I need itemAt() to return a pointer of the right type. I can get around this by having the derived items cast the QGraphicsItem * returned by QGraphicsScene::itemAt() using dynamic_cast, but I don't really understand why that works and not qobject_cast, or the benefits or disadvantages to using dynamic_cast vs. qobject_cast.

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  • Static linking in Qt --> link errors in VS 2008

    - by ChruS
    Today I dediced to make static linking in Qt. I used Qt4 with Visual Studio and static C runtime article. The 3rd step took quite a long time. When it was finished I opened my project in VS 2008, made Build->Clean Solution and try to Release. Unfortunately I got link errors: warning LNK4098: defaultlib 'libcmt.lib' conflicts with use of other libs; use /NODEFAULTLIB:library error LNK2019: unresolved external symbol "private: static struct QString::Data QString::shared_null" (?shared_null@QString@@0UData@1@A) referenced in function "public: __thiscall QString::QString(void)" (??0QString@@QAE@XZ) error LNK2019: unresolved external symbol "private: static struct QByteArray::Data QByteArray::shared_null" (?shared_null@QByteArray@@0UData@1@A) referenced in function "public: __thiscall QByteArray::QByteArray(void)" (??0QByteArray@@QAE@XZ) error LNK2001: unresolved external symbol "private: static struct QByteArray::Data QByteArray::shared_null" (?shared_null@QByteArray@@0UData@1@A) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2019: unresolved external symbol "public: static enum QSysInfo::WinVersion const QSysInfo::WindowsVersion" (?WindowsVersion@QSysInfo@@2W4WinVersion@1@B) referenced in function _WinMain@16 What i did wrong? Help to fix this pls.

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  • Static linking in Qt --> link errors in VS 2008

    - by ChruS
    Today I dediced to make static linking in Qt. I used Qt4 with Visual Studio and static C runtime article. The 3rd step took quite a long time. When it was finished I opened my project in VS 2008, made Build->Clean Solution and try to Release. Unfortunately I got link errors: warning LNK4098: defaultlib 'libcmt.lib' conflicts with use of other libs; use /NODEFAULTLIB:library error LNK2019: unresolved external symbol "private: static struct QString::Data QString::shared_null" (?shared_null@QString@@0UData@1@A) referenced in function "public: __thiscall QString::QString(void)" (??0QString@@QAE@XZ) error LNK2019: unresolved external symbol "private: static struct QByteArray::Data QByteArray::shared_null" (?shared_null@QByteArray@@0UData@1@A) referenced in function "public: __thiscall QByteArray::QByteArray(void)" (??0QByteArray@@QAE@XZ) error LNK2001: unresolved external symbol "private: static struct QByteArray::Data QByteArray::shared_null" (?shared_null@QByteArray@@0UData@1@A) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2019: unresolved external symbol "public: static enum QSysInfo::WinVersion const QSysInfo::WindowsVersion" (?WindowsVersion@QSysInfo@@2W4WinVersion@1@B) referenced in function _WinMain@16 What i did wrong? Help to fix this pls.

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  • Qt QFileDialog - native dialogs only with static functions?

    - by darron
    I'm trying to simply save a file. However, I need a filename entered without a suffix to automatically get a default suffix (which setDefaultSuffix() does). I'd rather not completely lose the native save dialog just for this. exec() is not overloaded from QDialog, so it totally bypasses the native hook (ignoring the DontUseNativeDialog option even if it's false). If I disable the file overwrite warning and append the default suffix myself after the function returns, then I'd be re-opening the dialog if the user did not want to overwrite... and that's just ugly. Is there some signal I can catch and quickly inject the default suffix if it's not there? I'm guessing not, since it's a native dialog. Is there something I'm doing wrong with the filter? I only have one filter choice. It should use that extension. This seems pretty lame. Launching the save dialog and simply typing "test" should never result in an extensionless file. "test.", yes. "test" no way. That'll really confuse the users when they hit Load and can't see the file they just saved. I guess the cross-platform part of Qt is giving me lowest common denominator file dialog functionality?

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  • Qt 5.3 OpenGL - vertex buffer object drawing using the core profile

    - by user3700881
    Im using Qt 5.3 to create a QWindow to do some basic rendering stuff. The QWindow is declared like this: class OpenGLWindow : public QWindow, protected QOpenGLFunctions_3_3_Core { Q_OBJECT ... } It is initialized in the constructor: OpenGLWindow::OpenGLWindow(QWindow *parent) : QWindow(parent) { QSurfaceFormat format; format.setVersion(3,3); format.setProfile(QSurfaceFormat::CoreProfile); this->setSurfaceType(OpenGLSurface); this->setFormat(format); this->create(); _context = new QOpenGLContext; _context->setFormat(format); _context->create(); _context->makeCurrent(this); this->initializeOpenGLFunctions(); ... } And that's the rendering code: void OpenGLWindow::render() { if(!isExposed()) return; _context->makeCurrent(this); glClear(GL_COLOR_BUFFER_BIT); glUseProgram(_shaderProgram); glBindBuffer(GL_ARRAY_BUFFER, _positionBufferObject); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); glDrawArrays(GL_TRIANGLES, 0, 3); glDisableVertexAttribArray(0); glUseProgram(0); _context->swapBuffers(this); } I am trying to draw a simple triangle using a vertex and fragment shader. The problem is that the triangle is not showing up when the core profile is set. Only when I set the OpenGL version to 2.0 or when I use the compatibility profile, it shows up. From my point of view that doesn't make any sense because I am not using fixed functionality at all. What am I missing?

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  • QT: custom widget in QScrollArea

    - by slimscsi
    I am attempting to create a custom widget. My Widget renders itself unless it is inside a scroll area. The code below works. If I change the if(0) to an if(1) inside the MainWindow constructor, it will not render the "Hello World" string. I assume that I must (re)implement some additional methods, but so far I have not been able to find the correct ones with trial and error. // hellowidget.h #ifndef HELLOWIDGET_H #define HELLOWIDGET_H #include <QtGui> class HelloWidget : public QWidget { Q_OBJECT public: HelloWidget(QWidget *parent = 0); void paintEvent(QPaintEvent *event); }; #endif // HELLOWIDGET_H // hellowidget.cpp #include "hellowidget.h" HelloWidget::HelloWidget(QWidget *parent) : QWidget(parent) { } void HelloWidget::paintEvent(QPaintEvent *event) { QPainter painter(this); painter.drawText(rect(), Qt::AlignCenter, "Hello World"); } // mainwindow.h #ifndef MAINWINDOW_H #define MAINWINDOW_H #include <QtGui> class MainWindow : public QMainWindow { Q_OBJECT public: MainWindow(QWidget *parent = 0); ~MainWindow(); private: }; #endif // MAINWINDOW_H // mainwindow.cpp #include "mainwindow.h" #include "hellowidget.h" MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent) { HelloWidget *hello = new HelloWidget; QWidget *central = hello; if( 0 ) { QScrollArea *scroll = new QScrollArea ; scroll->setWidget(hello); central = scroll; } setCentralWidget( central ); } MainWindow::~MainWindow() { } // main.cpp #include <QtGui/QApplication> #include "mainwindow.h" int main(int argc, char *argv[]) { QApplication a(argc, argv); MainWindow w; w.show(); return a.exec(); }

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  • Custom QAbstractGraphicsShapeItem very slow in Qt Jambi

    - by Mene
    I try to implement an own QAbstractGraphicsShapeItem in Qt Jambi (4.5) but as soon as I implement a custom class (rather than use e.g. QGraphicsEllipseItem) the rendering speed drops by about on order of magnitude. If looked in the original Code of QGraphicsEllipseItem and it seems to do basicly the same. class Circle extends QAbstractGraphicsShapeItem { final private QRectF rect = new QRectF(); public final void setRect(double x, double y, double w, double h) { QRectF newRect = new QRectF(x, y, w, h); if (!newRect.equals(rect)) { prepareGeometryChange(); this.rect.setX(x); this.rect.setY(y); this.rect.setWidth(w); this.rect.setHeight(h); this.update(rect); } } @Override public final QRectF boundingRect() { return rect; } QPainterPath shape; @Override public final QPainterPath shape() { if (shape == null) { QPainterPath path = new QPainterPath(); path.addEllipse(rect); QPainterPathStroker stroker = new QPainterPathStroker(); QPen pen = this.pen(); stroker.setCapStyle(pen.capStyle()); stroker.setWidth(pen.widthF()); shape = stroker.createStroke(path); } return shape; } @Override public final void paint(QPainter painter, QStyleOptionGraphicsItem option, QWidget widget) { painter.setPen(this.pen()); painter.setBrush(this.brush()); painter.drawEllipse(this.rect); } } I need to render a lot of objects and they are mostly moving, so speed is essential. Anyone knows how to speed this up? I underestand that Java might be slower then the nativ code in the library. But the code in the paint method seems not to be the problem, since commenting it out doesn't change the speed notably.

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  • Qt 101: Why can't I use this class?

    - by Airjoe
    I have experience with C++ but I've never really used Qt before. I'm trying to connect to a SQLite database, so I found a tutorial here and am going with that. In the QtCreator IDE, I went to Add New -- C++ Class and in the header file pasted in the header the header from that link and in the .cpp file I pasted the source. My main.cpp looks like this: #include <QtGui/QApplication> #include "mainwindow.h" #include "databasemanager.h" #include <qlabel.h> int main(int argc, char *argv[]) { QApplication a(argc, argv); MainWindow w; w.show(); DatabaseManager db(); QLabel hello("nothing..."); if(db.openDB()){ hello.setText("Win!"); } else{ hello.setText("Lame!"); } hello.resize(100, 30); hello.show(); return a.exec(); } And I'm getting this error: main.cpp:13: error: request for member 'openDB' in 'db', which is of non-class type 'DatabaseManager()' Can anyone point me in the right direction? I know "copypaste" code isn't good, I just wanted to see if I could get DB connectivity working and I figured something like this would be simple... thanks for the help.

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