If you have a `QMainWindow` you can override `closeEvent` method.



    #include &lt;QCloseEvent&gt;
    void MainWindow::closeEvent (QCloseEvent *event)
    {
        QMessageBox::StandardButton resBtn = QMessageBox::question( this, APP_NAME,
                                                                    tr(&quot;Are you sure?\n&quot;),
                                                                    QMessageBox::Cancel | QMessageBox::No | QMessageBox::Yes,
                                                                    QMessageBox::Yes);
        if (resBtn != QMessageBox::Yes) {
            event-&gt;ignore();
        } else {
            event-&gt;accept();
        }
    }
    
&lt;br&gt;If you&#39;re subclassing a `QDialog`, the `closeEvent` will not be called and so you have to override `reject()`:

    void MyDialog::reject()
    {
        QMessageBox::StandardButton resBtn = QMessageBox::Yes;
        if (changes) {
            resBtn = QMessageBox::question( this, APP_NAME,
                                            tr(&quot;Are you sure?\n&quot;),
                                            QMessageBox::Cancel | QMessageBox::No | QMessageBox::Yes,
                                            QMessageBox::Yes);
        }
        if (resBtn == QMessageBox::Yes) {
            QDialog::reject();
        }
    }

Well, I got it. One way is to override the [`QWidget::closeEvent`](http://doc.qt.io/qt-5/qwidget.html#closeEvent)`(QCloseEvent *event)` method in your class definition and add your code into that function. Example:

    class foo : public QMainWindow
    {
        Q_OBJECT
    private:
        void closeEvent(QCloseEvent *bar);
        // ...
    };

    
    void foo::closeEvent(QCloseEvent *bar)
    {
        // Do something
        bar-&gt;accept();
    }



You can attach a SLOT to the

    void aboutToQuit();

signal of your QApplication. This signal should be raised just before app closes.

also you can reimplement protected member QWidget::closeEvent()

    void YourWidgetWithXButton::closeEvent(QCloseEvent *event)
    {
    	// do what you need here
        // then call parent&#39;s procedure
    	QWidget::closeEvent(event);
    }



You can remove an item from a database using EF by using the following two methods.

 - [EntityCollection&lt;TEntity&gt;.Remove Method][1]

 - [ObjectContext.DeleteObject Method][2]


The first is on the `EntityCollection` and the second on the `ObjectContext`.

When should each be used? 

Is one prefered over the other?

`Remove()` returns a `bool` and `DeleteObject()` returns `void`.

  [1]: http://msdn.microsoft.com/en-us/library/bb337024.aspx
  [2]: http://msdn.microsoft.com/en-us/library/system.data.objects.objectcontext.deleteobject.aspx

Entity Framework .Remove() vs. .DeleteObject()

I&#39;m starting off with a numpy array of an image.

    In[1]:img = cv2.imread(&#39;test.jpg&#39;)

The shape is what you might expect for a 640x480 RGB image.

    In[2]:img.shape
    Out[2]: (480, 640, 3)

However, this image that I have is a frame of a video, which is 100 frames long. Ideally, I would like to have a single array that contains all the data from this video such that `img.shape` returns `(480, 640, 3, 100)`.

What is the best way to add the next frame -- that is, the next set of image data, another 480 x 640 x 3 array -- to my initial array?

How can I add new dimensions to a Numpy array?

I am developing an application using Qt. I don&#39;t know which slot corresponds to the event of &quot;the user clicking the &#39;X&#39;(close) button of the window frame&quot; i.e. this button:

![Close button of the window][1]

If there isn&#39;t a slot for this, can anyone suggest me some other method by which I can start a function after the user presses that close button.

  [1]: http://i.stack.imgur.com/rgFqm.png

Qt: How do I handle the event of the user pressing the &#39;X&#39; (close) button?

I am developing an application using Qt. I don't know which slot corresponds to the event of "the user clicking the 'X'(close) button of the window frame" i.e. this button:
<img src="http://i.stack.imgur.com/rgFqm.png" alt="Close button of the window">
If there isn't a slot for this, can anyone suggest me some other method by which I can start a function after the user presses that close button.

I have written a library that I used to compile using a self-written Makefile, but now I want to switch to cmake. The tree looks like this (I removed all the irrelevant files):

    .
    ├── include
    │&#160;&#160; ├── animation.h
    │&#160;&#160; ├── buffers.h
    │&#160;&#160; ├── ...
    │&#160;&#160; ├── vertex.h
    │&#160;&#160; └── world.h
    └── src
        ├── animation.cpp
        ├── buffers.cpp
        ├── ...
        ├── vertex.cpp
        └── world.cpp

So what I am trying to do is just to compile the source into a shared library and then install it with the header files.

Most examples that I have found compile executables with some shared libraries but never just a plain shared library.
It would also be helpful if someone could just tell me a very simple library that uses cmake, so I can use this as an example.

How to create a shared library with cmake?

Is it possible to develop a C++ program while using HTML and CSS for the user interface? I know about programming with Javascript using a Webkit container, but I am really interested in C++ development.

I felt in love with C# WPF when I developed under Windows, but now I moved to Linux and I haven&#39;t found a good tool for using markup for interfaces. For this, I would like to mix HTML and CSS, which are very lightweight and easy to use, with C++ code, with something like WPF.

Oh, one more thing: I&#39;m looking for desktop development, not web.

How to build native C++ apps with HTML/CSS UI?

In an interview I was confronted with a question such as this:   

&gt; Your friend has given you a single source code file which prints the
&gt; Fibonacci numbers on the console. Note that the main() block is
&gt; empty and doesn&#39;t have any statements inside it. 
 
&gt; Explain how this is possible (hint: global instance!) 

I really want to know about this, how such a thing can be even possible!

How is it possible to declare nothing inside main() in C++ and yet have a working application after compilation?

In C++11, you can use a `shared_ptr&lt;&gt;` to establish an ownership relation with an object or variable and `weak_ptr&lt;&gt;` to safely reference that object in a non-owned way.

You can also use `unique_ptr&lt;&gt;` to establish an ownership relation with an object or variable. But what if other, non-owning objects want to also reference that object? `weak_ptr&lt;&gt;` isn&#39;t helpful in this case. Raw pointers are helpful but bring various downsides (e.g. they can be [automatically initialized to nullptr][1] but this is accomplished through techniques that are not consistent with the `std::*_ptr&lt;&gt;` types).

What is the equivalent of `weak_ptr&lt;&gt;` for non-owning references to objects owned via `unique_ptr&lt;&gt;`?

Here&#39;s a clarifying example that resembles something in a game I&#39;m working on.

    class World
    {
    public:
    
        Trebuchet* trebuchet() const { return m_trebuchet.get(); }
    
    private:
        std::unique_ptr&lt; Trebuchet &gt; m_trebuchet;
    };
    
    class Victim
    {
    public:
        Victim( Trebuchet* theTrebuchet ) : m_trebuchet( theTrebuchet ) {}
    
        ~Victim()
        {
            delete m_trebuchet;     // Duh. Oops. Dumb error. Nice if the compiler helped prevent this.
        }
    
    private:
    
        Trebuchet* m_trebuchet;    // Non-owning.
    };
    
    shared_ptr&lt; Victim &gt; createVictim( World&amp; world )
    {
        return make_shared&lt; Victim &gt;( world.trebuchet() );
    }

Here we use a raw pointer to maintain a non-owning relationship with an object owned via `unique_ptr&lt;&gt;` elsewhere. But is raw the best we can do?

The hope is a type of pointer that:

* Looks like the other modern pointer types. E.g. `std::raw_ptr&lt;T&gt;`.
* Replaces raw pointers so that a codebase that uses modern pointer types throughout can find *all* pointers via a search for `_ptr&lt;` (roughly).
* Auto-initializes to nullptr.

Thus:

    int* p;                  // Unknown value.
    std::raw_ptr&lt; int &gt; p;   // null.

Does this type already exist in C++ now, is it proposed for the future, or is another implementation broadly available in e.g. Boost?

  [1]: https://stackoverflow.com/questions/17534210/trivial-raw-pointer-that-self-initializes-to-nullptr-in-c


shared_ptr&lt;&gt; is to weak_ptr&lt;&gt; as unique_ptr&lt;&gt; is to... what?

I want a way to serialize and deserialize Objects to JSON, as automatic as possible.

**Serialize:**
For me, the ideal way is that if I call in an instance JSONSerialize() it returns an string with a JSON object that has all the public properties of the object as ``&quot;name_of_property&quot;: &quot;value&quot;``.
For those values that are primitives, it is straightforward, for objects it should try to call on each JSONSerialize() or ToString() or something like that to recursively serialize all the public properties.
For collections it should also behave correctly (just vectors/arrays will be ok).

**Deserialize**: Just make an instance of the given object (let&#39;s say a dog) and call ``JSONDeserialize(json_string)``, and that should fill all the public properties, creating the needed objects in case that the properties are not primitives, or the needed collections.

An example should run like that:

    Dog *d1 = new Dog();
    d1-&gt;name = &quot;myDog&quot;;

    string serialized = d1-&gt;JSONSerialize();
    
    Dog *d2 = new Dog();
    d2-&gt;JSONDeserialize(serialized);
    std::cout &lt;&lt; d2-&gt;name; // This will print &quot;myDog&quot;

Or like that:

    Dog *d1 = new Dog();
    d1-&gt;name = &quot;myDog&quot;;

    string serialized = JSONSerializer.Serialize(d1);
    
    Dog *d2 = JSONSerializer.Deserialize(serialized, Dog);
    std::cout &lt;&lt; d2-&gt;name; // This will print &quot;myDog&quot;

How can I pull this off easily?

C++ JSON Serialization

I have a `QLabel` in my application that displays error messages to the user. I would like to make the text of the label selectable so users can copy and paste the error message if needed.

However, when I use the mouse to click and drag over the text, nothing happens - the text is not selected.

How can I make the text within a `QLabel` selectable by the mouse?

Make QLabel text selectable?

I just reinstalled QtCreator, created new project (*Qt Application*) an got this after compilation: 

    /usr/bin/ld: **cannot find -lGL**
    collect2: error: ld returned 1 exit status
    make: *** [untitled1] Error 1
    18:07:41: The process &quot;/usr/bin/make&quot; exited with code 2.
    Error while building/deploying project untitled1 (kit: Desktop Qt 5.1.0 GCC 32bit)
    When executing step &#39;Make&#39;

(*Project is empty, I did&#39;n commit any changes*)

&gt; Qt Creator 2.7.2  
Based on Qt 5.1.0 (32 bit)  
Ubuntu 13.04

How do I solve this problem?

Qt: can&#39;t find -lGL error

I am porting code from qt4 to qt5. I added the following line to my `.pro` file, [as suggested][1]:
  
    QT += webkitwidgets

However, when I run `qmake`, I get the this error:

    Project ERROR: Unknown module(s) in QT: webkitwidgets

I am developing on Ubuntu 12.04 LTS and installed Qt [as described][2].


  [1]: http://qt-project.org/wiki/Transition_from_Qt_4.x_to_Qt5
  [2]: https://askubuntu.com/questions/279421/how-can-i-install-qt-5-x-on-12-04-lts

Project ERROR: Unknown module(s) in QT: webkitwidgets

I want to code a notification window at the bottom right corner of the desktop, so it works like Skype notifications when someone comes online. Can someone help me get the screen size of the desktop, so I can place my notification window at the bottom right corner using my Qt Application?

How can I find the screen/desktop size in Qt, so I can display a desktop notification?

I&#39;m developing a program in Qt. Its makefile is generated automatically from the .pro file. I need to use some code which need the -std=c++11 flag to be set up for g++. Where in .pro should I add this flag? (changing only the Makefile won&#39;t work since it gets overwritten by the newly generated one, each time I build the project).

Content Type	Original Author	Original Content on Stackoverflow
Question	Shravan	View Question on Stackoverflow
Solution 1 - C++	asclepix	View Answer on Stackoverflow
Solution 2 - C++	Shravan	View Answer on Stackoverflow
Solution 3 - C++	Sebastian Lange	View Answer on Stackoverflow
Solution 4 - C++	Alexander	View Answer on Stackoverflow

Qt: How do I handle the event of the user pressing the 'X' (close) button?

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

Solution 3 - C++

Solution 4 - C++

How can I add new dimensions to a Numpy array?

Entity Framework .Remove() vs. .DeleteObject()

Attributions