Goal
I want to benchmark some drawing libraries and gather diagnostics. I thought of implementing in each benchmark the same interface and then instantiating different classes in the main window.
The Challenge
The problem is that some benchmarks use QWidget and other QOpenGLWidget. So even if I implement the same functionality I can not use it, without dynamic casting to each possible instance.
What I tried so far
My first thought was to create an interface and use virtual multiple inheritance. But that doesn't seem to work and I am not sure if that's even the right solution.
I also thought of the Composite Pattern or Adapter Pattern, but seem some problems, as I want to override some functions of QWidget like resizeEvent in each benchmark. Of course I could duplicate that code or put it into some non-member function. But maybe there is something more elegant?
QWidgets Addin
class BenchmarkAddin : virtual public QWidget {
public:
BenchmarkAddin() {
connect(&timer_, SIGNAL(timeout()), this, SLOT(update()));
}
double get_fps() {
// use frames_ and time to estimate fps
}
void count_frame() {
++frames_;
}
void set_parameters(int param1_) {
param1_;
}
protected:
void resizeEvent(QResizeEvent* event) override {
init();
}
virtual void init() = 0;
int param1_;
private:
int frames_;
QTimer timer_;
}
Raster Benchmark
class RasterBenchmark : public BenchmarkAddin {
protected:
void init() override {
// create buffers
}
void paintEvent(QPaintEvent* event) override {
// do drawing using param1_
count_frame();
}
}
OpenGL benchmark
class OpenGLBenchmark : virtual public QOpenGLWidget, public BenchmarkAddin {
protected:
void paintGL() override {
// do GL drawing using param1_
count_frame();
}
}
Main Window Example Usage
BenchmarkAddin *widget;
if (benchmark == "raster") {
widget = new RasterBenchmark(this);
else
widget = new OpenGLBenchmark(this);
widget.set_parameters(100);
...
std::cout << widget.get_fps() << std::endl;
Obviously this doesn't work, as QOpenGLWidget doesn't use virtual inheritance for QWidget. Also there is a problem with Qt's object meta system.
Question:
Any idea how I could implement an interface that is both accessible within a subclass of QWidget and QOpenGLWidget?
Related
I'm using QGraphicsScene and I would like to have some items which emit signals when they are moved around.
Unfortunately, QGraphicsPixmapItem doesn't have any signals, so I subclassed it:
class InteractiveGraphicsPixmapItem : public QObject, public QGraphicsPixmapItem
{
Q_OBJECT
public:
InteractiveGraphicsPixmapItem();
InteractiveGraphicsPixmapItem(QPixmap pm) : QGraphicsPixmapItem(pm)
{
setFlag(QGraphicsItem::ItemIsMovable, true);
setAcceptedMouseButtons(Qt::LeftButton|Qt::RightButton);
}
private:
void mouseMoveEvent(QGraphicsSceneMouseEvent *);
signals:
void moved_by_mouse(QPointF newpos);
};
InteractiveGraphicsPixmapItem::InteractiveGraphicsPixmapItem()
{
}
void InteractiveGraphicsPixmapItem::mouseMoveEvent(QGraphicsSceneMouseEvent *)
{
emit moved_by_mouse(this->pos());
}
However, it is not movable.
If I change it back into a QGraphicsPixmapItem in the main program, and call item->setFlags(QGraphicsItem::ItemIsMovable); it becomes movable. For my custom class, it doesn't.
item = new InteractiveGraphicsPixmapItem(QPixmap(":/img/icon.png"));
scene->addItem(item);
item->setFlags(QGraphicsItem::ItemIsMovable);
A similar question was asked about selectability, and it was suggested that the setAcceptedMouseButtons(Qt::LeftButton|Qt::RightButton); must be added to the constructor. It didn't help in my case.
If you override the mouseMoveEvent, and don't call the base class's function, it won't move and you'll have to handle it yourself.
However, simply calling the base class function is all you need here
void InteractiveGraphicsPixmapItem::mouseMoveEvent(QGraphicsSceneMouseEvent* evt)
{
QGraphicsPixmapItem::mouseMoveEvent(evt);
emit moved_by_mouse(this->pos());
}
Also note that if you override one of the mouse events (press / release / move) you should also handle the others too.
I would like to derive all of my widgets from a base class widget that automatically establishes a signal/slot connection between a slot for the class and a (rarely called) signal.
The slot is a virtual function, so that any widgets for which I wish to implement custom functionality can derive from the virtual slot function. In the desired scenario, all my widgets would derive from this base class with the virtual slot, so that by default all of my widget instances would be connected to the desired signal with a slot defined for the object (with default behavior from the base class).
I know that virtual slots are allowed in Qt. However, deriving from two QObject classes is not supported, so that, for example, the following code is disallowed:
class MySignaler : public QObject
{
Q_OBJECT
public:
MySignaler : QObject(null_ptr) {}
signals:
void MySignal();
}
MySignaler signaler;
class MyBaseWidget: public QObject
{
Q_OBJECT
public:
MyBaseWidget() : QObject(null_ptr)
{
connect(&signaler, SIGNAL(MySignal()), this, SLOT(MySlot()));
}
public slots:
virtual void MySlot()
{
// Default behavior here
}
}
// Not allowed!
// Cannot derive from two different QObject-derived base classes.
// How to gain functionality of both QTabWidget and the MyBaseWidget base class?
class MyTabWidget : public QTabWidget, public MyBaseWidget
{
Q_OBJECT
public slots:
void MySlot()
{
// Decide to handle the signal for custom behavior
}
}
As the sample code demonstrates, it seems impossible to gain both the benefits of (in this example) the QTabWidget, and also the automatic connection from the desired signal function to the virtual slot function.
Is there some way, in Qt, to have all my application's widget classes share common base-class slot and connect() functionality while allowing my widgets to nonetheless derive from Qt widget classes such as QTabWidget, QMainWindow, etc.?
Sometimes when inheritance is problematic, one can replace it, or a part of it, with composition.
That's the approach needed in Qt 4: instead of deriving from a QObject, derive from a non-QObject class (MyObjectShared) that carries a helper QObject that is used as a proxy to connect the signal to its slot; the helper forwards that call to the non-QObject class.
In Qt 5, it is not necessary to derive from a QObject at all: signals can be connected to arbitrary functors. The MyObjectShared class remains the same.
Should Qt 4 compatibility be generally useful in other areas of the code, one can use a generic connect function that connects signals to functors in both Qt 4 and Qt 5 (in Qt 4, it would use an implicit helper QObject).
// https://github.com/KubaO/stackoverflown/tree/master/questions/main.cpp
#include <QtCore>
#include <functional>
#include <type_traits>
class MySignaler : public QObject {
Q_OBJECT
public:
Q_SIGNAL void mySignal();
} signaler;
#if QT_VERSION < 0x050000
class MyObjectShared;
class MyObjectHelper : public QObject {
Q_OBJECT
MyObjectShared *m_object;
void (MyObjectShared::*m_slot)();
public:
MyObjectHelper(MyObjectShared *object, void (MyObjectShared::*slot)())
: m_object(object), m_slot(slot) {
QObject::connect(&signaler, SIGNAL(mySignal()), this, SLOT(slot()));
}
Q_SLOT void slot() { (m_object->*m_slot)(); }
};
#endif
class MyObjectShared {
Q_DISABLE_COPY(MyObjectShared)
#if QT_VERSION < 0x050000
MyObjectHelper helper;
public:
template <typename Derived>
MyObjectShared(Derived *derived) : helper(derived, &MyObjectShared::mySlot) {}
#else
public:
template <typename Derived, typename = typename std::enable_if<
std::is_base_of<MyObjectShared, Derived>::value>::type>
MyObjectShared(Derived *derived) {
QObject::connect(&signaler, &MySignaler::mySignal,
std::bind(&MyObjectShared::mySlot, derived));
}
#endif
bool baseSlotCalled = false;
virtual void mySlot() { baseSlotCalled = true; }
};
class MyObject : public QObject, public MyObjectShared {
Q_OBJECT
public:
MyObject(QObject *parent = nullptr) : QObject(parent), MyObjectShared(this) {}
// optional, needed only in this immediately derived class if you want the slot to be a
// real slot instrumented by Qt
#ifdef Q_MOC_RUN
void mySlot();
#endif
};
class MyDerived : public MyObject {
public:
bool derivedSlotCalled = false;
void mySlot() override { derivedSlotCalled = true; }
};
void test1() {
MyObject base;
MyDerived derived;
Q_ASSERT(!base.baseSlotCalled);
Q_ASSERT(!derived.baseSlotCalled && !derived.derivedSlotCalled);
signaler.mySignal();
Q_ASSERT(base.baseSlotCalled);
Q_ASSERT(!derived.baseSlotCalled && derived.derivedSlotCalled);
}
int main(int argc, char *argv[]) {
test1();
QCoreApplication app(argc, argv);
test1();
return 0;
}
#include "main.moc"
To share some code between two QObjects, you could have the QObject as a member of the class,an interposing non-object class that uses generic class that's parametrized only on the base type. The generic class can have slots and signals. They must be made visible to moc only in the immediately derived class - and not in any further derived ones.
Alas, you generally cannot connect any of the generic class's signals or slots in the constructor of the class, since at that point the derived class isn't constructed yet, and its metadata isn't available - from Qt's perspective, the signals and slots don't exist as such. So the Qt 4-style runtime-checked connect will fail.
The compile-time-checked connect will not even compile, because the this pointer it works on has an incorrect compile-time type, and you know nothing about the type of the derived class.
A workaround for Qt-4 style connect only is to have a doConnections method that the derived constructor has to call, where the connections are made.
Thus, let's make the generic class parametric on the base and the derived class as well - the latter is known as the Curiously Recurring Template Pattern, or CRTP for short.
Now you have access to the derived class's type, and can use a helper function to convert this to a pointer to the derived class, and use it in the Qt 5-style compile-time-checked connects.
The Qt 4-style runtime checked connect still needs to be invoked from doConnections. So,if you use Qt 5, that's not an issue. You shouldn't be using Qt 4-style connect in Qt 5 code anyway.
The slots require slightly different treatment depending on whether the class immediately derived from the generic class overrides them or not.
If a slot is virtual and has an implementation in the immediately derived class, you should expose it to moc in the normal fashion - using a slots section or the Q_SLOT macro.
If a slot doesn't have an implementation in the immediately derived class (whether virtual or not), its implementation in the generic class should be made visible to moc only, but not to the compiler - you don't wish to override it, after all. Thus the slot declarations are wrapped in #ifdef Q_MOC_RUN block that is only active when moc is reading the code. The generated code will refer to the generic implementations of the slots.
As we wish to make sure this indeed works, we'll add some booleans to track whether the slots were invoked.
// main.cpp
#include <QtWidgets>
template <class Base, class Derived> class MyGenericView : public Base {
inline Derived* dthis() { return static_cast<Derived*>(this); }
public:
bool slot1Invoked, slot2Invoked, baseSlot3Invoked;
MyGenericView(QWidget * parent = 0) : Base(parent),
slot1Invoked(false), slot2Invoked(false), baseSlot3Invoked(false)
{
QObject::connect(dthis(), &Derived::mySignal, dthis(), &Derived::mySlot2); // Qt 5 style
QObject::connect(dthis(), &Derived::mySignal, dthis(), &Derived::mySlot3);
}
void doConnections() {
Q_ASSERT(qobject_cast<Derived*>(this)); // we must be of correct type at this point
QObject::connect(this, SIGNAL(mySignal()), SLOT(mySlot1())); // Qt 4 style
}
void mySlot1() { slot1Invoked = true; }
void mySlot2() { slot2Invoked = true; }
virtual void mySlot3() { baseSlot3Invoked = true; }
void emitMySignal() {
emit dthis()->mySignal();
}
};
The generic class is very simple to use. Remember to wrap any non-virtual overridden slots in a moc-only guard!
Also recall the general rule that applies to all Qt code: if you have a slot, it should be declared to moc only once. So, if you had a class that further derives from MyTreeWidget or MyTableWidget, you don't want a Q_SLOT or slots macro in front of any necessarily virtual slot overrides. If present, it'll subtly break things. But you definitely want Q_DECL_OVERRIDE.
If you're on Qt 4, remember to call doConnections, otherwise the method is unnecessary.
The particular choice of QTreeWidget and QTableWidget is completely arbitrary, meaningless, and shouldn't be taken to mean that such use makes any sense (it likely doesn't).
class MyTreeWidget : public MyGenericView<QTreeWidget, MyTreeWidget> {
Q_OBJECT
public:
bool slot3Invoked;
MyTreeWidget(QWidget * parent = 0) : MyGenericView(parent), slot3Invoked(false) { doConnections(); }
Q_SIGNAL void mySignal();
#ifdef Q_MOC_RUN // for slots not overridden here
Q_SLOT void mySlot1();
Q_SLOT void mySlot2();
#endif
// visible to the C++ compiler since we override it
Q_SLOT void mySlot3() Q_DECL_OVERRIDE { slot3Invoked = true; }
};
class LaterTreeWidget : public MyTreeWidget {
Q_OBJECT
public:
void mySlot3() Q_DECL_OVERRIDE { } // no Q_SLOT macro - it's already a slot!
};
class MyTableWidget : public MyGenericView<QTreeWidget, MyTableWidget> {
Q_OBJECT
public:
MyTableWidget(QWidget * parent = 0) : MyGenericView(parent) { doConnections(); }
Q_SIGNAL void mySignal();
#ifdef Q_MOC_RUN
Q_SLOT void mySlot1();
Q_SLOT void mySlot2();
Q_SLOT void mySlot3(); // for MOC only since we don't override it
#endif
};
Finally, this little test case shows that it indeed works as desired.
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MyTreeWidget tree;
MyTableWidget table;
Q_ASSERT(!tree.slot1Invoked && !tree.slot2Invoked && !tree.slot3Invoked);
emit tree.mySignal();
Q_ASSERT(tree.slot1Invoked && tree.slot2Invoked && tree.slot3Invoked);
Q_ASSERT(!table.slot1Invoked && !table.slot2Invoked && !table.baseSlot3Invoked);
emit table.mySignal();
Q_ASSERT(table.slot1Invoked && table.slot2Invoked && table.baseSlot3Invoked);
return 0;
}
#include "main.moc"
This approach gives you the following:
The common code class derives from the base class, and can thus easily invoke or override the behavior of the base class. In this particular example, you can reimplement the QAbstractItemView methods etc.
There is full support for signals and slots. Even though the signals and slots are declared as such in the metadata of the derived class, you can still use them in the generic class.
In this situation you may make use of composition rather than multiple inheritance. Something like this:
class MySignaler : public QObject
{
Q_OBJECT
public:
MySignaler : QObject(NULL) {}
signals:
void MySignal();
}
MySignaler signaler;
class MyBaseWidgetContainer: public QWidget
{
Q_OBJECT
public:
MyBaseWidgetContainer() : QObject(NULL), widget(NULL)
{
connect(&signaler, SIGNAL(MySignal()), this, SLOT(MySlot()));
}
public slots:
virtual void MySlot()
{
// Default behavior here
}
private:
QWidget *widget;
}
class MyTabWidgetContainer : public MyBaseWidgetContainer
{
Q_OBJECT
public:
MyTabWidgetContainer() {
widget = new QTabWidget(this);
QLayout *layout = new QBoxLayout(this);
layout->addWidget(widget);
}
public slots:
void MySlot()
{
// Decide to handle the signal for custom behavior
}
}
I am writing for the Qt framework and I want to create a QWidget. QWidget exposes some interfaces such as mousePressEvent and mouseReleaseEvent. I want to extend this class to allow mouseClickEvent and mouseDoubleClickEvent. Normally, you would think to extend QWidget and implement those functions. The problem is that there are other classes (QPushButton for example) provided as part of the library which extend QWidget. Therefore, how do I get that added functionality into those classes without having to extend each one and copy the code?
class ClickHandeler : public QWidget {
virtual void mouseClickEvent();
virtual void mouseDoubleClickEvent();
int clickCount; //initialized to 0;
void mouseReleaseEvent(QEvent *event){
clickCount++;
QTimer::singleShot(500, this, SLOT(checkClick()));
}
void checkClick(){
if (clickCount == 2){
this->mouseDoubleClickEvent();
clickCount = clickCount-2;
} else {
this->mouseDoubleEvent()
clickCount--;
}
}
}
// QPushButton inherits QWidget too! Yikes!
class MyPushButton : public QPushButton, public ClickHandeler {
void mouseClickEvent(){
alert("i have been clicked");
}
void mouseDoubleClickEvent(){
alert("i have been double clicked");
}
}
I want something like MyPushButton, but I am worried that the function overriding will not work as expected.
Im sorry if this question is obvious to people, but I do not know what the terminology is. I have googled interfaces for c++ and I get abstract interfaces (which doesnt properly solve this problem). If I'm just being stupid and need to know a better term for google, let me know in the comments and Ill remove the question.
I think you just need to extend the QWidget and call the QWidget same functions.
For example:
class QWidget {
public:
void mouseClickEvent();
};
class QPushButton {
public:
void mouseClickEvent();
};
class MyWidget : public QWidget, public QPushButton {
public:
void mouseClickEvent()
{
//base::mouseClickEvent();// ambiguous
QWidget::mouseClickEvent();
QPushButton::mouseClickEvent();
/* Do your own code here */
}
};
Following case:
Let's say there is a binary library which defines the class "Base", and many subclasses ("Derivative1", "Derivative2" etc) of it.
I want to extend these subclasses in my own code, but because my extensions are the same for all subclasses as they only deal with parts of Base, it would be tedious to subclass every Derivative class and add the same code over and over again.
My first idea was to simply write a class template which would do the work for me, but because the library I'm dealing with is Qt, QObject has foiled me.
My second idea was to use macros to generate each class structure, but this was also thwarted by moc.
The "reparent" in the title is because I thought of deriving from Base and creating BaseExtended, and then somehow tell the compiler to reparent every Derivative to this extended class. Isn't there a way to for example declare the "Base" in "BaseExtended" virtual, and then just write
class Derivative1Extended : public Derivative1, public BaseExtended {}
and have the virtual Base in BaseExtended point to the Base in Derivative1, thus basically "squeezing ing" my extensions between Base and Derivative1?
(By the way, I tried to keep the above as generic as possible, but what I'm actually doing is trying add signals for "focusIn" and "focusOut" to every QWidget derivative without writing the same code over and over again for every QWidget subclass I use)
EDIT:
For reference, here's my current implementation:
// qwidgetfs.h
class QLineEditFS : public QLineEdit
{
Q_OBJECT
private:
void focusInEvent(QFocusEvent *);
void focusOutEvent(QFocusEvent *);
public:
QLineEditFS(QWidget *parent = 0);
signals:
void focusReceived(QWidgetFS::InputType);
void focusLost();
};
// qwidgetfs.cpp
QLineEditFS::QLineEditFS(QWidget *parent /*= 0*/)
: QLineEdit(parent)
{}
void QLineEditFS::focusInEvent(QFocusEvent *e)
{
QLineEdit::focusInEvent(e);
emit focusReceived(QWidgetFS::InputText);
}
void QLineEditFS::focusOutEvent(QFocusEvent *e)
{
QLineEdit::focusOutEvent(e);
emit focusLost();
}
And this repeated for QSpinBoxFS, QComboBoxFS, QCheckBoxFS and so on...
Instead I would like to just define this logic in a common class QWidgetFS, and then "inject" it into other classes derived from QWidget
I'm not sure you'll really be able to do what you are suggesting without modifying Qt and recompiling it.
Perhaps to do what you want, you could use event filters installed on the objects that you want to handle focus events from?
little test app:
header:
class FocusEventFilter : public QObject
{
Q_OBJECT
public:
FocusEventFilter(QObject* parent)
: QObject(parent)
{}
Q_SIGNALS:
void focusIn(QWidget* obj, QFocusEvent* e);
void focusOut(QWidget* obj, QFocusEvent* e);
protected:
bool eventFilter(QObject *obj, QEvent *e);
};
class testfocus : public QMainWindow
{
Q_OBJECT
public:
testfocus(QWidget *parent = 0, Qt::WFlags flags = 0);
~testfocus();
public Q_SLOTS:
void onFocusIn(QWidget*, QFocusEvent*);
void onFocusOut(QWidget*, QFocusEvent*);
private:
Ui::testfocusClass ui;
};
Implementation
#include <QFocusEvent>
#include "testfocus.h"
bool FocusEventFilter::eventFilter(QObject *obj, QEvent *e)
{
if (e->type() == QEvent::FocusIn) {
bool r = QObject::eventFilter(obj, e);
QFocusEvent *focus = static_cast<QFocusEvent*>(e);
QWidget* w = qobject_cast<QWidget*>(obj);
if (w) {
emit focusIn(w, focus);
}
return r;
}
else if (e->type() == QEvent::FocusOut) {
bool r = QObject::eventFilter(obj, e);
QFocusEvent *focus = static_cast<QFocusEvent*>(e);
QWidget* w = qobject_cast<QWidget*>(obj);
if (w) {
emit focusOut(w, focus);
}
return r;
}
else {
// standard event processing
return QObject::eventFilter(obj, e);
}
}
testfocus::testfocus(QWidget *parent, Qt::WFlags flags)
: QMainWindow(parent, flags)
{
ui.setupUi(this);
FocusEventFilter* filter = new FocusEventFilter(this);
ui.lineEdit->installEventFilter(filter);
ui.lineEdit_2->installEventFilter(filter);
connect(filter, SIGNAL(focusIn(QWidget*, QFocusEvent*)), this, SLOT(onFocusIn(QWidget*, QFocusEvent*)));
connect(filter, SIGNAL(focusOut(QWidget*, QFocusEvent*)), this, SLOT(onFocusOut(QWidget*, QFocusEvent*)));
}
testfocus::~testfocus()
{
}
void testfocus::onFocusIn(QWidget* obj, QFocusEvent*)
{
obj->setStyleSheet("background-color:#aaaaff;");
}
void testfocus::onFocusOut(QWidget* obj, QFocusEvent*)
{
obj->setStyleSheet("background-color:#ffaaaa;");
}
Of course, YMMV. You could always have a separate filter per object. This method means you can avoid deriving from everything. Not as efficient but it should work.
You may be able to do what you want in the event filter itself rather than using signals/slots.
I have done stuff like this in the past with templates. The problem is that you can't use signals.
I'm typing this up without a compiler so please be kind :):
template<typename T>
class FSWidget: public T
{
public:
FSWidget()
{
_delegate = NULL;
}
setDelegate(FSDelegate *delegate)
{
_delegate = delegate;
}
protected:
virtual void focusInEvent(QFocusEvent *e)
{
T::focusInEvent(e);
if (_delegate) {
_delegate->focusInEvent(this);
}
}
virtual void focusOutEvent(QFocusEvent *e)
{
T::focusOutEvent(e);
if (_delegate) {
_delegate->focusOutEvent(this);
}
}
private:
FSDelegate *_delegate;
};
So, the advantage is when you need to use this you can basically create a class like this:
FSWidget<QLineEdit *> lineEdit = new FSWidget<QLineEdit *>;
lineEdit->setDelegate(delegate);
You can put in whatever you want instead of QLineEdit and it will work.
And then teh FSDelegate could be just an interface that you mix into whatever class needs to act on the info. It could be one of these:
class FSDelegate
{
public:
virtual void focusInEvent(QWidget *w) = 0;
virtual void focusOutEvent(QWidget *w) = 0;
};
If you're always doing the same thing in on focusInEvent and focusOutEvents, you can implement these functions and make a real Mixin class.
Hopefully this can avoid some code duplication for you.
I have 5 classes that interact (maintaining professionally, not author). My problem is that the code that is emitting the signal (there is just one, code below) is never activating the slot (MyWidget::HandleMeasurementChanged). This system has a large degree of complexity. I have tried to reduce that, but think the complexity likely contributes to the problem. There is also a high rate of calls to Observer::notify, but most of these will get filtered out by code that I have not posted here and the Emit calls are fairly rare. If anyone could help point me to why the slot is not getting activated, I'd really appreciate it. It is almost acting like the MyWidget class instance is not processing its event loop. I have had a little success setting the connect type to Direct Connection, but since the emit is in a separate thread and the production code for the slot will update the UI I have ruled that out as a final solution.
class IObserver { public: virtual void notify()=0; };
class ExternalMeasurement { ... };
class Measurement { public: Measurement(ExternalMeasurement source); };
class Observer : public QThread, public IObserver
{
signals:
void MeasurementChanged(boost::shared_ptr<Measurement> measurement);
public:
//called by 3rd party in separate thread
virtual void notify(ExternalMeasurement measurement)
{
_measurement_ =
boost::shared_ptr<Measurement>(new Measurement(measurement));
emit MeasurementChanged(_measurement);
}
private:
boost::shared_ptr<Measurement> _measurement_;
};
class MyWidget : public QWidget
{
private:
Component _component_;
public slots:
void HandleMeasurementChanged(boost::shared_ptr<Measurement> measurement);
public:
MyWidget(Component * component_)
};
MyWidget::MyWidget(Component * component_)
{
_component_ = component_;
connect(
_component_->_observer_,
MeasurementChanged(boost::shared_ptr<Measurement> measurement),
this,
HandleMeasurementChanged(boost::shared_ptr<Measurement> measurement));
}
class Component
{
private:
QApplication * _application_;
MyWidget * _widget_;
Observer * _observer_;
public:
void MainFunc();
}
void Component::MainFunc()
{
_observer_ = new Observer();
...
_application_ = new QApplication(...);
...
_widget_ = new MyWidget(...);
...
_widget_->show();
_application_->exec();
}
This was referenced in the link that Jeremy added in a comment to my question, but just for clarity:
The solution was to add:
qRegisterMetaType<shared_ptr<Measurement> >("shared_ptr<Measurement>");
immediately before the call to connect.