C++ Qt Widget app: catch mouse signals from a QPixmap?

[Tom asso]

I suspect this has a simple answer, but I'm missing something about signals and slots. My C++ MainWindow class creates a QPixmap - how can a member function receive signals emitted when the user clicks the mouse within the QPixmap?

I tried this approach:

MainWindow.h:

protected:
  QPixmap pixmap_;

private slots:
  void mySlot(QMouseEvent *event);

MainWindow.cpp:

pixmap_ = 
   new QPixmap(width, height);

// Connect QPixmap mouse press signal 
// to MainWindow slot
  connect(pixmap_, 
          some-signal-here?
          this,
          &MainWindow::mySlot);

What signal should MainWindow catch? Do I have to subclass QPixmap to make this happen?

Thanks!

[Pl45m4]

@Tom-asso

Search for "Clickable Label" or something.

There is even an entry on Qt Wiki for that:

• https://wiki.qt.io/Clickable_QLabel

Then you just have to use QLabel::setPixmap(yourPixmap) to assign the image to it.

Edit:

Usually there is no need to "new" a QPixmap. Using a stack variable is sufficient most of the time.

[ChrisW67]

@Tom-asso A QPixmap is an in-memory structure holding an image, not something that a user can click on. If you want a user to click on a displayed version of this image then you need to put it on a widget that a user can interact with (e.g. QLabel). The widget can handle mouse click events, map that to a point in the image, and emit a signal carrying that information.

[Pl45m4]

@Tom-asso

Search for "Clickable Label" or something.

There is even an entry on Qt Wiki for that:

• https://wiki.qt.io/Clickable_QLabel

Then you just have to use QLabel::setPixmap(yourPixmap) to assign the image to it.

Edit:

Usually there is no need to "new" a QPixmap. Using a stack variable is sufficient most of the time.