Help with QWidget::show()

[mmikeinsantarosa]

I need to call a function when a QWidget gets its show() method gets called and I have looked at examples for Mainwindow but I don't understand how this works.
The widget that needs to implement show() is called ChartProperties. For declaring it in the header,
void MainWindow::showEvent(QShowEvent *ev);
doesn't work because this isn't a mainwindow and
void ChartProperties::showEvent(QShowEvent *ev)
complains about an extra member showevent.

Any suggestions would be much appreciated.

I'm clueless here and thanks for any response.

[SGaist]

Hi,

@mmikeinsantarosa said in Help with QWidget::show():

I have irtual void showEvent(QShowEvent *event) override;

This is just a declaration, you still have to implement the function itself.

[Christian Ehrlicher]

@mmikeinsantarosa said in Help with QWidget::show():

void ChartProperties::showEvent(QShowEvent *ev)
complains about an extra member showevent.

What exact error message do you get?

[mmikeinsantarosa]

@Christian-Ehrlicher said in Help with QWidget::show():

void ChartProperties::showEvent(QShowEvent *ev)

I get "extra qualification on member 'showEvent'"

[mmikeinsantarosa]

And the widget is actually a "QDialog".

[Christian Ehrlicher]

And please show how you defined and declared this function.

[mmikeinsantarosa]

Realizing that the class is actually a QDialog so I just changed the declaration to
virtual void showEvent(QShowEvent *event) override;
and it doesn't complain now.

So now, how do I hook it up to execute another function?
Right clicking on it and selecting refactor doesn't provide a way to create a function in my source. Do I need to create a slot to connect it to?

[Christian Ehrlicher]

@mmikeinsantarosa said in Help with QWidget::show():

So now, how do I hook it up to execute another function?

I don't understand this question. Simply create a function in your class and call it from within your other function.

[mmikeinsantarosa]

Sorry, I'm feeling pretty dumb here.

Another class executes the ChartProperties->Show() method and when the dialog is rendered, I want to trap the ChartProperties show() event.
I have irtual void showEvent(QShowEvent *event) override;
in my ChartProperties header but I don't understand how to receive the showEvent..

[Christian Ehrlicher]

As explained in the documentation this function is called when the widget is shown, you must not call it by yourself.

[SGaist]

Hi,

@mmikeinsantarosa said in Help with QWidget::show():

I have irtual void showEvent(QShowEvent *event) override;

This is just a declaration, you still have to implement the function itself.

[mmikeinsantarosa]

Do I create a slot then connect this event to my slot?

[Christian Ehrlicher]

@mmikeinsantarosa said in Help with QWidget::show():

Do I create a slot then connect this event to my slot?

What slot? showEvent() is a class function, not a slot. Please learn C++ basics first.

[mpergand]

@mmikeinsantarosa

Your question seems pretty close this this one

As an alternative, you can simply do:

MyDialog::show()
{
  myFunction();
  QDialog::show();
}

Using showEvent is dangerous cause it can be called multi times !

[mmikeinsantarosa]

The method name is "showEvent" which leads me to think it's a signal. It's also listed in the signals list in the documentation for QDialog so I thought it might actually be a signal.

thanks for clearing this up SGaist.

[SGaist]

@mmikeinsantarosa said in Help with QWidget::show():

It's also listed in the signals list in the documentation for QDialog

That's wrong, neither in the Qt 5 nor in the Qt 6 documentation.

It is listed under Reimplemented Protected Functions.

Beside that, signals name do not finish in "event". They usually have a name in relation to some action like rejected in QDialog.

[mmikeinsantarosa]

I stand corrected. entering QDialog in the Qt help and selecting signals reveals signals at the top, with 3 items under it then Reimplemented Protected Functions where the showEvent function is listed.

[JonB]

@mmikeinsantarosa
Indeed, that is how Qt documentation lays out its methods.

To reiterate something @Christian-Ehrlicher said. In Qt nomenclature:

• Methods ending in Event (showEvent(), mouseMoveEvent()) are not signals. Instead they are protected virtual methods. You must sub-class and override if you want to access them.

• Signals tend to be named as the past tense of something that has happened (clicked(), customContextMenuRequested()). You cannot override them. You can connect() to them, without needing to sub-class.

• And slots are just named as an action to be performed (show(), setDiabled()).