In one of my project I managed to fix a bug switching from a std::vector of objects to a std::vector of pointers to the object. Using the debugger I found that the error occurred when I was calling the std::vector<T,Allocator>::clear that it is supposed to destroy the objects stored in the vector. I am happy I solved the issue but I would like to know why I was able to!
Here I attach the code incriminated:
#include <vector>
#include <memory>
#include <string>
class Base
{
public:
Base(int a);
Base(const Base& o)=default;
Base& operator=(const Base& o)=default;
Base(Base&& o)=default;
Base& operator=(Base&& o)=default;
virtual ~Base()=default;
virtual void Do();
};
class Derived: public Base
{
private:
std::string b;
public:
Derived(int a, std::string& b) : Base(a), b(b) {}
};
//Other derived classes from Base overriding Do
class Main{
private:
std::vector<Derived> v;
public:
Main();
void Do(int i, std::string& b){
/*
if something happens
v.emplace_back(a, b);// push_back equivalently for our purpose
if something else happens
v.erase(iterator)
*/
}
void reset(){
v.clear();
}
};
class Main1{
private:
std::vector<std::unique_ptr<Derived>> v;
public:
Main1();
void Do(int i, std::string& b){
/*
if something happens
v.push_back(std::unique_ptr<Derived>(new Derived(i, b)));
if something else happens
v.erase(iterator)
*/
}
void reset(){
v.clear();
}
};
int main()
{
Main m;
for(int i=0; i<101; ++i){
//something
m.Do(i, b);
//something
if(i%10==0)
m.reset(); //The bug is here. If I use Main1 everything runs smoothly
}
return 0;
}
This is a simplified version of the code that creates me problem. I hope that the detail are enough to give the correct contest for the answer.
The debugger points me deep in the code defining what a deconstructor does reporting a segmentation fault, and personally I cannot understand what that code does.
The compiler I am using is g++ 10.1 with the std=c++17 flag.
I'm making some GUI through QT.
I almost complete my work but I have a hard time dealing with Qthread.
My goal is to measure the position of the motor (it moves) and display it on the Qtextbrowser while working another function in the main thread. When I wrote codes like below, people said I can't use QTextBrowser(Qwidget) directly in the thread, so I'm searching how to return location value to the main thread. Can you do me a favor?
MDCE is a class in another header and the codes I attach are some parts of my first code.
void MotorPort::StartThread(MDCE* com, QTextBrowser* browser)
{
thread1 = QThread::create(std::bind(&MotorPort::MeasureLocation,this,com,browser));
thread1 -> start();
}
void MotorPort::MeasureLocation(MDCE* com, QTextBrowser* browser)
{
double location;
while(1)
{
location = CurrentLocation(com); \\return current position value
browser->setText(QString::number(location));
if (QThread::currentThread()->isInterruptionRequested()) return ;
}
}
void MotorPort::stopMeasure()
{
thread1->requestInterruption();
if (!thread1->wait(3000))
{
thread1->terminate();
thread1->wait();
}
thread1 = nullptr;
}
You should use the Qt signal/slot mechanism for iter-thread notification such as this. Firstly change your MotorPort class definition to declare a signal location_changed...
class MotorPort: public QObject {
Q_OBJECT;
signals:
void location_changed(QString location);
...
}
Now, rather than MotorPort::MeasureLocation invoking QTextBrowser::setText directly it should emit the location_changed signal...
void MotorPort::MeasureLocation (MDCE *com, QTextBrowser *browser)
{
while (true) {
double location = CurrentLocation(com);
/*
* Emit signal to notify of location update.
*/
emit location_changed(QString::number(location));
if (QThread::currentThread()->isInterruptionRequested())
return ;
}
}
Finally, update MotorPort::StartThread to connect the signal to the browser's setText slot...
void MotorPort::StartThread (MDCE *com, QTextBrowser *browser)
{
connect(this, &MotorPort::location_changed, browser, &QTextBrowser::setText);
thread1 = QThread::create(std::bind(&MotorPort::MeasureLocation, this, com, browser));
thread1->start();
}
So far, I understand that we have two threads in QML, our main application thread, and our "scene graph" thread : http://doc.qt.io/qt-5/qtquick-visualcanvas-scenegraph.html
I've implemented my own vtkQmlItem with the help of this link : http://doc.qt.io/qt-5/qtquick-scenegraph-openglunderqml-example.html
and I've noticed that my vtkscene is only rendered when the afterrendering signal is emitted by the qml flow.
So far, everything is ok and works perfectly, I can see my vtk scene and can even interract with it.
But I would like to also programmatically render my vtk scene as well, since I want to do an animation by moving the camera around a vtk object.
Calling renderer->render() directly shows a lot of vtk error, and does not seem to be the good way to do this.
Calling this->window()->update() seems to put the event in the eventLoop, when I want it to be handled instantly. The only way I've managed to make it work instantly is by using QApplication::processEvents(), which is a hack I don't like and would love another solution.
So the pseudocode of the working solution that I don't like is the following :
for (int i = 0; i < 50; i++)
{
ChangeCameraPosition(i); // Change the position and orientation of the vtk camera
this->window()->update();
QApplication::processEvents(); // The hack I don't like
QThread::msleep(500);
}
For people looking for a solution for this using Qt QuickControls 2 and VTK 8, you can find a working example in this repository https://github.com/nicanor-romero/QtVtk with building instructions in the README.
the problem is actually a bit complicated and if nothing changed in the past few months, there is still no support for QtQuick in VTK, which means no simple few lines solution. You can find support classes for QtWidgets in VTK/GUISupport/QtOpenGL/ and use them as a template to derive support for qml. But mainly I recommend checking this thread for a discussion about this topic.
The key point is that QtQuick holds the openGL context for the qml window you are trying to render into in a dedicated thread and it won't let anything else get that context. So in order to render into it from VTK, you have to do it within that thread. This means:
1) Create your own vtkRenderWindow that overrides the Render() method such that it is ensured it happens in the qml's render thread.
2) Make that render window render into a framebuffer object provided by the qtquick (instance of QQuickFramebufferObject).
3) Interconnect vtk's rendering signals with the qt's rendering methods -> e.g. when the vtk render window calls makeCurrent, the qt's rendering thread "wakes up".
Here is my implementation based on Taylor Braun-Jones' template linked above. It might not be perfect, but it works for me (I have removed some parts specific to my app so it might not compile straight away, but it should put you on a path to some working solution):
qmlVtk.h:
#include <vtkEventQtSlotConnect.h>
#include <vtkGenericOpenGLRenderWindow.h>
#include <vtkRenderer.h>
#include <QtQuick/QQuickFramebufferObject>
// Use the OpenGL API abstraction from Qt instead of from VTK because vtkgl.h
// and other Qt OpenGL-related headers do not play nice when included in the
// same compilation unit
#include <QOpenGLFunctions>
#include <qqmlapplicationengine.h>
class QVTKFramebufferObjectRenderer;
class QVTKInteractorAdapter;
class vtkInternalOpenGLRenderWindow;
class QVTKFramebufferObjectRenderer;
class QVTKFrameBufferObjectItem : public QQuickFramebufferObject
{
Q_OBJECT
public:
QVTKFrameBufferObjectItem(QQuickItem *parent = 0);
~QVTKFrameBufferObjectItem();
Renderer *createRenderer() const;
vtkSmartPointer<vtkInternalOpenGLRenderWindow> GetRenderWindow() const;
protected:
// Called once before the FBO is created for the first time. This method is
// called from render thread while the GUI thread is blocked.
virtual void init();
vtkSmartPointer<vtkInternalOpenGLRenderWindow> m_win;
QVTKInteractorAdapter* m_irenAdapter;
vtkSmartPointer<vtkEventQtSlotConnect> mConnect;
friend class QVTKFramebufferObjectRenderer;
// Convert the position of the event from openGL coordinate to native coordinate
QMouseEvent openGLToNative(QMouseEvent const& event);
virtual void mouseMoveEvent(QMouseEvent * event);
virtual void mousePressEvent(QMouseEvent * event);
virtual void mouseReleaseEvent(QMouseEvent * event);
virtual void mouseDoubleClickEvent(QMouseEvent * event);
virtual void wheelEvent(QWheelEvent *event);
virtual void keyPressEvent(QKeyEvent* event);
virtual void keyReleaseEvent(QKeyEvent* event);
virtual void focusInEvent(QFocusEvent * event);
virtual void focusOutEvent(QFocusEvent * event);
protected Q_SLOTS:
// slot to make this vtk render window current
virtual void MakeCurrent();
// slot called when vtk wants to know if the context is current
virtual void IsCurrent(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
// slot called when vtk wants to start the render
virtual void Start();
// slot called when vtk wants to end the render
virtual void End();
// slot called when vtk wants to know if a window is direct
virtual void IsDirect(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
// slot called when vtk wants to know if a window supports OpenGL
virtual void SupportsOpenGL(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
};
/// <summary>
/// An extension of vktGenericOpenGLRenderWindow to work with Qt.
/// Serves to write VTK-generated render calls to a framebuffer provided and maintained by Qt. It is meant to be used within Qt render loop, i.e. using Qt's render thread.
/// </summary>
/// <seealso cref="vtkGenericOpenGLRenderWindow" />
/// <seealso cref="QOpenGLFunctions" />
class vtkInternalOpenGLRenderWindow : public vtkGenericOpenGLRenderWindow, protected QOpenGLFunctions
{
public:
static vtkInternalOpenGLRenderWindow* New();
vtkTypeMacro(vtkInternalOpenGLRenderWindow, vtkGenericOpenGLRenderWindow)
virtual void OpenGLInitState();
// Override to use deferred rendering - Tell the QSG that we need to
// be rendered which will then, at the appropriate time, call
// InternalRender to do the actual OpenGL rendering.
virtual void Render();
// Do the actual OpenGL rendering
void InternalRender();
// Provides a convenient way to set the protected FBO ivars from an existing
// FBO that was created and owned by Qt's FBO abstraction class
// QOpenGLFramebufferObject
void SetFramebufferObject(QOpenGLFramebufferObject *fbo);
QVTKFramebufferObjectRenderer *QtParentRenderer;
protected:
vtkInternalOpenGLRenderWindow();
~vtkInternalOpenGLRenderWindow()
{
// Prevent superclass destructors from destroying the framebuffer object.
// QOpenGLFramebufferObject owns the FBO and manages it's lifecyle.
this->OffScreenRendering = 0;
}
};
qmlVtk.cpp:
#include "QVTKFramebufferObjectItem.h"
#include <QQuickFramebufferObject>
#include <QQuickWindow>
#include <QOpenGLFramebufferObject>
#include <QVTKInteractorAdapter.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkObjectFactory.h>
#include <vtkSmartPointer.h>
#include <vtkCamera.h>
#include <vtkProperty.h>
#include <qglfunctions.h>
class QVTKFramebufferObjectRenderer : public QQuickFramebufferObject::Renderer
{
friend class vtkInternalOpenGLRenderWindow;
public:
QVTKFramebufferObjectRenderer(vtkSmartPointer<vtkInternalOpenGLRenderWindow> rw) :
m_framebufferObject(0)
{
m_vtkRenderWindow = rw;
m_vtkRenderWindow->QtParentRenderer = this;
}
~QVTKFramebufferObjectRenderer()
{
m_vtkRenderWindow->QtParentRenderer = 0;
glFrontFace(GL_CCW); // restore default settings
}
virtual void synchronize(QQuickFramebufferObject * item)
{
// the first synchronize call - right before the the framebufferObject
// is created for the first time
if (!m_framebufferObject)
{
QVTKFrameBufferObjectItem *vtkItem = static_cast<QVTKFrameBufferObjectItem*>(item);
vtkItem->init();
}
}
virtual void render()
{
m_vtkRenderWindow->InternalRender(); // vtkXOpenGLRenderWindow renders the scene to the FBO
}
QOpenGLFramebufferObject *createFramebufferObject(const QSize &size)
{
QOpenGLFramebufferObjectFormat format;
format.setAttachment(QOpenGLFramebufferObject::Depth);
m_framebufferObject = new QOpenGLFramebufferObject(size, format);
m_vtkRenderWindow->SetFramebufferObject(m_framebufferObject);
return m_framebufferObject;
}
vtkSmartPointer<vtkInternalOpenGLRenderWindow> m_vtkRenderWindow;
QOpenGLFramebufferObject *m_framebufferObject;
};
vtkStandardNewMacro(vtkInternalOpenGLRenderWindow);
vtkInternalOpenGLRenderWindow::vtkInternalOpenGLRenderWindow() :
QtParentRenderer(0)
{
vtkOpenGLRenderWindow::OpenGLInitContext();
}
void vtkInternalOpenGLRenderWindow::OpenGLInitState()
{
this->MakeCurrent();
vtkOpenGLRenderWindow::OpenGLInitState();
// Before any of the gl* functions in QOpenGLFunctions are called for a
// given OpenGL context, an initialization must be run within that context
initializeOpenGLFunctions();
glFrontFace(GL_CW); // to compensate for the switched Y axis
}
void vtkInternalOpenGLRenderWindow::InternalRender()
{
vtkOpenGLRenderWindow::Render();
}
//
// vtkInternalOpenGLRenderWindow Definitions
//
void vtkInternalOpenGLRenderWindow::Render()
{
this->QtParentRenderer->update();
}
void vtkInternalOpenGLRenderWindow::SetFramebufferObject(QOpenGLFramebufferObject *fbo)
{
// QOpenGLFramebufferObject documentation states that "The color render
// buffer or texture will have the specified internal format, and will
// be bound to the GL_COLOR_ATTACHMENT0 attachment in the framebuffer
// object"
this->BackLeftBuffer = this->FrontLeftBuffer = this->BackBuffer = this->FrontBuffer =
static_cast<unsigned int>(GL_COLOR_ATTACHMENT0);
// Save GL objects by static casting to standard C types. GL* types
// are not allowed in VTK header files.
QSize fboSize = fbo->size();
this->Size[0] = fboSize.width();
this->Size[1] = fboSize.height();
this->NumberOfFrameBuffers = 1;
this->FrameBufferObject = static_cast<unsigned int>(fbo->handle());
this->DepthRenderBufferObject = 0; // static_cast<unsigned int>(depthRenderBufferObject);
this->TextureObjects[0] = static_cast<unsigned int>(fbo->texture());
this->OffScreenRendering = 1;
this->OffScreenUseFrameBuffer = 1;
this->Modified();
}
void QVTKFrameBufferObjectItem::Start()
{
m_win->OpenGLInitState();
}
void QVTKFrameBufferObjectItem::End()
{
}
void QVTKFrameBufferObjectItem::MakeCurrent()
{
this->window()->openglContext()->makeCurrent(this->window());
}
void QVTKFrameBufferObjectItem::IsCurrent(vtkObject*, unsigned long, void*, void* call_data)
{
bool* ptr = reinterpret_cast<bool*>(call_data);
*ptr = this->window()->openglContext();
}
void QVTKFrameBufferObjectItem::IsDirect(vtkObject*, unsigned long, void*, void* call_data)
{
int* ptr = reinterpret_cast<int*>(call_data);
*ptr = QGLFormat::fromSurfaceFormat(this->window()->openglContext()->format()).directRendering();
}
void QVTKFrameBufferObjectItem::SupportsOpenGL(vtkObject*, unsigned long, void*, void* call_data)
{
int* ptr = reinterpret_cast<int*>(call_data);
*ptr = QGLFormat::hasOpenGL();
}
QVTKFrameBufferObjectItem::QVTKFrameBufferObjectItem(QQuickItem *parent) : QQuickFramebufferObject(parent)
{
setAcceptedMouseButtons(Qt::AllButtons);
m_irenAdapter = new QVTKInteractorAdapter(this);
m_win = vtkSmartPointer<vtkInternalOpenGLRenderWindow>::New();
// make a connection between the vtk signals and qt slots so that an initialized and madeCurrent opengl context is given to the vtk
// we probably need only the Start(), MakeCurrent() and End() one, but just to be sure...
mConnect = vtkSmartPointer<vtkEventQtSlotConnect>::New();
mConnect->Connect(m_win, vtkCommand::WindowMakeCurrentEvent, this, SLOT(MakeCurrent()));
mConnect->Connect(m_win, vtkCommand::WindowIsCurrentEvent, this, SLOT(IsCurrent(vtkObject*, unsigned long, void*, void*)));
mConnect->Connect(m_win, vtkCommand::StartEvent, this, SLOT(Start()));
mConnect->Connect(m_win, vtkCommand::EndEvent, this, SLOT(End()));
mConnect->Connect(m_win, vtkCommand::WindowIsDirectEvent, this, SLOT(IsDirect(vtkObject*, unsigned long, void*, void*)));
mConnect->Connect(m_win, vtkCommand::WindowSupportsOpenGLEvent, this, SLOT(SupportsOpenGL(vtkObject*, unsigned long, void*, void*)));
}
QVTKFrameBufferObjectItem::~QVTKFrameBufferObjectItem()
{
mConnect->Disconnect(); // disconnect all slots
if (m_irenAdapter)
delete m_irenAdapter;
}
QQuickFramebufferObject::Renderer *QVTKFrameBufferObjectItem::createRenderer() const
{
return new QVTKFramebufferObjectRenderer(m_win);
}
vtkSmartPointer<vtkInternalOpenGLRenderWindow> QVTKFrameBufferObjectItem::GetRenderWindow() const
{
return m_win;
}
void QVTKFrameBufferObjectItem::init()
{
}
// theoretically not needed now - the Y is being flipped in render and devicePixelRatio will almost always be = 1 on a PC anyway...but lets keep it to be sure
QMouseEvent QVTKFrameBufferObjectItem::openGLToNative(QMouseEvent const& event)
{
QPointF localPos(event.localPos());
localPos.setX(localPos.x() * window()->devicePixelRatio());
localPos.setY(localPos.y() * window()->devicePixelRatio());
QMouseEvent nativeEvent(event.type(), localPos, event.button(), event.buttons(), event.modifiers());
return nativeEvent;
}
void QVTKFrameBufferObjectItem::mouseMoveEvent(QMouseEvent * event)
{
m_win->GetInteractor()->SetSize(this->width(), this->height());
QMouseEvent nativeEvent = openGLToNative(*event);
m_irenAdapter->ProcessEvent(&nativeEvent, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::mousePressEvent(QMouseEvent * event)
{
m_win->GetInteractor()->SetSize(this->width(), this->height());
QMouseEvent nativeEvent = openGLToNative(*event);
m_irenAdapter->ProcessEvent(&nativeEvent, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::mouseReleaseEvent(QMouseEvent * event)
{
m_win->GetInteractor()->SetSize(this->width(), this->height());
QMouseEvent nativeEvent = openGLToNative(*event);
m_irenAdapter->ProcessEvent(&nativeEvent, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::wheelEvent(QWheelEvent *event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::keyPressEvent(QKeyEvent* event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::keyReleaseEvent(QKeyEvent* event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::focusInEvent(QFocusEvent * event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::focusOutEvent(QFocusEvent * event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
To use it, define an instance of the framebuffer in your qml form and stretch it across the window you want to render into, e.g. like this (assuming you registered the QVTKFrameBufferObjectItem as a QVTKFrameBuffer in qml e.g. like this qmlRegisterType<QVTKFrameBufferObjectItem>("VtkQuick", 1, 0, "QVTKFrameBuffer");):
import VtkQuick 1.0
QVTKFrameBuffer
{
id: renderBuffer
anchors.fill : parent
Component.onCompleted :
{
myCppDisplay.framebuffer = renderBuffer // tell the c++ side of your app that this is the framebuffer into which it should render
}
}
You then use the vtkRenderWindow you get by myCppDisplay.framebuffer.GetRenderWindow() the same way you would use any other vtkRenderWindow if you were rendering into a vtk-managed window, i.e. you can assign vtkRenderer to it, assign actors to that renderer, call theWindow.Render() as you wish and it will all be rendered into the qml component to which you assigned the framebuffer.
Two notes: 1) the vtk and qt use different coordinate system, you need to flip the y-coordinate...I am doing it by assigning a scale transformation to the camera, but there is plenty of other ways to do it:
vtkSmartPointer<vtkTransform> scale = vtkSmartPointer<vtkTransform>::New();
scale->Scale(1, -1, 1);
renderer->GetActiveCamera()->SetUserTransform(scale);
2) things get quite tricky once you start using multiple threads - you have to make sure that you are not trying to render in two different threads, because they would compete for that one QtQuick's rendering thread. This does not mean only not calling renderWindow.Render() in parallel - that is easy to avoid - but you have to realize that that qt thread is used also for rendering the GUI, so you might get into trouble this way (updating GUI while doing VTK rendering).
I tried implementing this example and have successfully compiled and ran it as well but I am facing some challenges with respect to the code.
I am not able to figure out where these lines are defined as they are giving me runtime errors and are not getting recognized as well.
(Defined in qmlVtk.cpp -> SetFramebufferObject() function)
this->NumberOfFrameBuffers = 1;
this->FrameBufferObject = static_cast<unsigned int>(fbo->handle());
this->DepthRenderBufferObject = 0;
this->TextureObjects[0] = static_cast<unsigned int>(fbo->texture());
this->OffScreenRendering = 1;
this->OffScreenUseFrameBuffer = 1;
Also, can anyone guide me as how to integrate QML with OpenGLWidget.
This is my btconnect.h file
#ifndef BTCONNECT_H
#define BTCONNECT_H
#include "scandialog.h"
namespace Ui {
class BTConnect;
}
class BTConnect : public QWidget
{
Q_OBJECT
public:
explicit BTConnect(QWidget *parent = 0);
~BTConnect();
private slots:
void on_ScanButton_clicked();
void ScanBTDevices();
//some slots here
void ScanDialogShow();
void ScanDialogClose();
public slots:
//some slots here
private:
Ui::BTConnect *ui;
QProcess BTscan_Process;
scanDialog *scan;
};
#endif // BTCONNECT_H
btconnect.cpp
BTConnect::BTConnect(QWidget *parent) :
QWidget(parent),
ui(new Ui::BTConnect)
{
//set the userinterface as BTConnect.ui
ui->setupUi(this);
scan = new scanDialog(this);
}
void BTConnect::ScanDialogShow()
{
scan->show();
}
void BTConnect::ScanDialogClose()
{
scan->close();
}
void BTConnect::ScanBTDevices()
{
ScanDialogShow();
//Command to scan nearby bluetooth devices
//"hcitool scan"
QString cmd("hcitool scan");
//start the process
BTscan_Process.start(cmd);
//Wait for the processs to finish with a timeout of 20 seconds
if(BTscan_Process.waitForFinished(20000))
{
//Clear the list widget
this->ui->listWidget->clear();
//Read the command line output and store it in QString out
QString out(BTscan_Process.readAllStandardOutput());
//Split the QString every new line and save theve in a QStringList
QStringList OutSplit = out.split("\n");
//Parse the QStringList in btCellsParser
btCellsParser cp(OutSplit);
for(unsigned int i = 0; i<cp.count(); i++)
{
//writing in listwidget
}
}
ScanDialogClose();
}
void BTConnect::on_ScanButton_clicked()
{
//Scan for available nearby bluetooth devices
ScanBTDevices();
}
if I use the above code, the qdialog scandialog does open when the process begins and closes when the data is loaded in qlistwidget, but the contents of qdialog scandialog are not displayed. If I were to change show() to exec(), the contents will be shown but the QProcess does not run until the dialog is closed.
I want the dialog to open when the Qprocess starts and close when the qlistwidget is loaded with data from the scan. And I want the contents of scandialog to be displayed. It has two labels. One with .GIF file and another with text saying scanning.
Any help is appreciated.
you never return to the event loop when you do show (because of waitForFinished) and you never continue to the processing code when you do exec
instead of the waitForFinished you should connect to the finished signal and handle it there and use a single shot timer that will cancel it:
void BTConnect::on_BTscanFinished()//new slot
{
//Clear the list widget
this->ui->listWidget->clear();
//Read the command line output and store it in QString out
QString out(BTscan_Process.readAllStandardOutput());
//Split the QString every new line and save theve in a QStringList
QStringList OutSplit = out.split("\n");
//Parse the QStringList in btCellsParser
btCellsParser cp(OutSplit);
for(unsigned int i = 0; i<cp.count(); i++)
{
//writing in listwidget
}
ScanDialogClose();
}
void BTConnect::ScanBTDevices()
{
ScanDialogShow();
//Command to scan nearby bluetooth devices
//"hcitool scan"
QString cmd("hcitool scan");
//start the process
connect(BTscan_Process, SIGNAL(finished()), this, SLOT(on_BTscanFinished()));
BTscan_Process.start(cmd);
QTimer::singleShot(20000, scan, SLOT(close()));
}
The problem is that QDialog::exec and QProcess::waitForFinished functions block event loop. Never ever block event loop. So you just need to do things more asynchronously.
QProcess class can be handled asynchronously using signals like readReadStandardOutput. And QDialog can be shown asynchronously using open slot.
The example:
void ScanBTDevices() {
// Open dialog when process is started
connect(process, SIGNAL(started()), dialog, SLOT(open()));
// Read standard output asynchronously
connect(process, SIGNAL(readyReadStandardOutput()), SLOT(onReadyRead()));
// Start process asynchronously (for example I use recursive ls)
process->start("ls -R /");
}
void onReadyRead() {
// Write to list widget
dialog->appendText(QString(process->readAllStandardOutput()));
}
The data will be appended to the dialog during generating by process.
Also using QProcess::finished signal and you can close the dialog.
I am creating a Qt application and I added dynamic translation (I followed the example at http://www.qtcentre.org/wiki/index.php?title=Dynamic_translation_in_Qt4_applications) with a QCombobox which lists different languages. It works well but the problem is that I don't see how to translate dynamically the text in the dialog windows (for example YES and NO buttons).
In the main.cpp, before executing the app, I have :
QTranslator qtTranslator;
qtTranslator.load("qt_" + QLocale::system().name(), QLibraryInfo::location(QLibraryInfo::TranslationsPath));
a.installTranslator(&qtTranslator);
which translate the dialog Windows in the user system language but I would like to do it dynamically like the rest of my app.
Here are the code of the example :
application.h :
#ifndef APPLICATION_H
#include <QApplication>
#include <QHash>
#include <QStringList>
class QDir;
class QTranslator;
typedef QHash<QString, QTranslator*> Translators;
class Application : public QApplication
{
Q_OBJECT
public:
explicit Application(int& argc, char* argv[]);
~Application();
static void loadTranslations(const QString& dir);
static void loadTranslations(const QDir& dir);
static const QStringList availableLanguages();
public slots:
static void setLanguage(const QString& locale);
private:
static QTranslator* current;
static Translators translators;
//static QTranslator* qtTranslator;//test to translate dialog windows
};
#endif // APPLICATION_H
application.cpp :
#include <QDir>
#include <QFileInfo>
#include <QTranslator>
#include <QLibraryInfo>
#include "application.h"
QTranslator* Application::current = 0;
//QTranslator* Application::qtTranslator = 0;//test to translate dialog windows
Translators Application::translators;
Application::Application(int& argc, char* argv[])
: QApplication(argc, argv)
{
}
Application::~Application()
{
}
void Application::loadTranslations(const QString& dir)
{
loadTranslations(QDir(dir));
QString locale = QLocale::system().name().section('_', 0, 0);
QString language=locale+ "_" + locale;
if(!QFile::exists(":Localization/Localization/"+language+".qm"))//if system language is not available, load english version
setLanguage("en_en");
else
setLanguage(language);
}
void Application::loadTranslations(const QDir& dir)
{
// <language>_<country>.qm
QString filter = "*_*.qm";
QDir::Filters filters = QDir::Files | QDir::Readable;
QDir::SortFlags sort = QDir::Name;
QFileInfoList entries = dir.entryInfoList(QStringList() << filter, filters, sort);
foreach (QFileInfo file, entries)
{
// pick country and language out of the file name
QStringList parts = file.baseName().split("_");
QString language = parts.at(parts.count() - 2);
QString country = parts.at(parts.count() - 1);
// construct and load translator
QTranslator* translator = new QTranslator(instance());
if (translator->load(file.absoluteFilePath()))
{
QString locale = language + "_" + country;
translators.insert(locale, translator);
}
}
}
const QStringList Application::availableLanguages()
{
// the content won't get copied thanks to implicit sharing and constness
return QStringList(translators.keys());
}
void Application::setLanguage(const QString& locale)
{
//test to translate dialog windows
/*
QTranslator qtTranslator;
QString qTLocale=locale.mid(0,2);
qtTranslator->load("qt_"+ qTLocale, QLibraryInfo::location(QLibraryInfo::TranslationsPath));
installTranslator(qtTranslator);
//*/
// remove previous
if (current)
{
removeTranslator(current);
}
// install new
current = translators.value(locale, 0);
if (current)
{
installTranslator(current);
}
}
I added the lines commented with "//test to translate dialog Windows" to try the dynamic translation of the dialog Windows but it doesn't work (no error at compilation but the application isn't launched with error message "the program stopped suddenly", I am on Qt Creator). Thanks!
So I finally got this to work after having the same problems. There are two things which were wrong in my case:
Name of the qt translation file:
QTranslator qtTranslator;
qtTranslator.load("qt_de"); // worked in older qt versions
qtTranslator.load("qtbase_de"); // works for qt5.2
a.installTranslator(&qtTranslator);
Have the correct parent for the QMessageBox. This is obvious after you think about it but pretty easy to miss.
QMessageBox::information(someChildOfMainWindow, ...);
For the latter, if you happen to be in a class which is a QObject but not a QWidget you can also use the following code to access your MainWindow from anywhere:
QMainWindow* mw = 0;
foreach(QWidget* widget, QApplication::topLevelWidgets()) {
if(widget->objectName() == "<your-main-window-class-name-here>") {
mw = qobject_cast<QMainWindow>(widget);
}
}
Ok Sébastian Lange, so finally I created the box and didn't use the static ones (
QMessageBox::question(..) for example)
QMessageBox quitMessageBox;
quitMessageBox.setWindowTitle(tr("Quit"));
quitMessageBox.setWindowIcon(QIcon("myIcon.jpg"));
quitMessageBox.setIcon(QMessageBox::Question);
quitMessageBox.setText(tr("Quit the application?"));
quitMessageBox.setStandardButtons(QMessageBox::Yes | QMessageBox::No);
quitMessageBox.setDefaultButton(QMessageBox::No);
quitMessageBox.button(QMessageBox::Yes)->setText(tr("Yes"));
quitMessageBox.button(QMessageBox::No)->setText(tr("No"));
And then
quitMessageBox.exec();
Like that it's ok. Thanks again!
When providing buttons for the dialog use
tr("Yes")
as for default dialogs, the created .ts-language file (to be edited via QtLinguist) should have default translations included.
The tr() marks the given argument to be translated. This concludes to if you do not know what will be written on a given label, you cannot translate it...