Capture scroll event in textEditor

danga96

hello to the whole community Qt Forum,
I would like to know if there is a way to capture the scroll event in a text editor; I have tried installing an eventfilter and captured these events:

bool TextEdit::eventFilter(QObject* obj, QEvent* event) {
	if (event->type() == QEvent::GraphicsSceneWheel){}
	if (event->type() == QEvent::Wheel){}
	if (event->type() == QEvent::Scroll){}
	return true;
}

but they don't work, only "Wheel" is captured when you reach the beginning and the end of the scroll area
Thanks in advance :)

raven-worx

@danga96 said in Capture scroll event in textEditor:

I have tried installing an eventfilter

installed where? on the widget itself or on it's viewport widget?

danga96

Thanks for the reply; I did it like this:

textEdit = new QTextEdit(this);
textEdit->installEventFilter(this);

raven-worx

@danga96
then try
textEdit->viewport()->installEventFilter(this);

danga96

@raven-worx said in Capture scroll event in textEditor:

textEdit->viewport()->installEventFilter(this);

thanks a lot, now it goes with the mouse, but if a user uses the scrollbar the event is not captured, how can I do?

raven-worx

@danga96
What are you exactly trying to achieve?

danga96

@raven-worx said in Capture scroll event in textEditor:

What are you exactly trying to achieve?

in practice, I would like to launch a function whenever a scroll occurs; in particular, on my text I have labels, which act as some kind of little clouds, which must follow the text, so if this scrolls upwards the label must also follow it;

raven-worx

@danga96
then its easier to subclass QTextEdit:

void MyTextEdit::scrollContentsBy(int dx, int dy) {
   // scroll happened, do whatever you want here
   QTextEdit::scrollContentsBy(dx, dy);
}

danga96

@raven-worx
sorry again, but how can I use this virtual method? do i need to make a connect?

jsulm

@danga96 said in Capture scroll event in textEditor:

do i need to make a connect?

No, you simply override it in your class (scrollContentsBy is called by Qt framework). This is how virtual methods are used: if a subclass overrides it then its own implementation is called, else the implementation in the base class is called.

danga96

@raven-worx said in Capture scroll event in textEditor:
@jsulm
thanks for answering me, but I can't get it to work; if I declare the method like this:

QTextEdit::scrollContentsBy(int dx,int dy);

it works, but not belonging to the class I can't exceed the private variables;
do i have to do anything in .h, adding some define?
in the .h I have tried:

void scrollContentsBy(int dx, int dy) override;

and in .cpp:

void TextEdit::scrollContentsBy(int dx, int dy) { }

and I get this error in compilation: "method with override specifier 'override' did not override any base class methods"

jsulm

@danga96 Is your class derived from QTextEdit?

class MyTextEdit : public QTextEdit
{
...
};

danga96

now yes, but the class already inherits from QMainWindow, and I don't know if this creates conflicts, so is there a way to do it through a connect?

jsulm

@danga96 I don't get it: you want to capture scroll events in QTextEdit but in your QMainWindow? That can't work.
Create a new class as subclass of QTextEdit and use that subclass instead of QTextEdit...
Also, is MyTextEdit really derived from QMainWindow?! If so then this is really a bad name.

danga96

@jsulm
I'm referring to this example: richtext-textedit
I'm using it to do tests; at this point I would ask you how I can adapt this with the solution proposed by you?

jsulm

@danga96 The solution wasn't proposed by me.
In the textedit.h file you will find this line:

QTextEdit *textEdit;

Replace it with your own class derived from QTextEdit:

MyOwnTextEdit *textEdit;

In myowntextedit.h

class MyOwnTextEdit : public QTextEdit
{
    ...
    void scrollContentsBy(int dx, int dy) override;
    ...
}

danga96

@jsulm said in Capture scroll event in textEditor:
thank you very much, and I apologize in advance for the insistence, but in this way I have to modify almost everything, because I will have to create a new class and adapt all the changes I have made with this new type, only to manage the scroll event;
Therefore I would like to know if there is another way.

danga96

finally I solved this way:

connect(textEdit->verticalScrollBar(), &QScrollBar::valueChanged, this, &TextEdit::handleUsersCursors);
	
connect(textEdit->horizontalScrollBar(), &QScrollBar::valueChanged, this, &TextEdit::handleUsersCursors);

without creating a new class;
thanks anyway for the tips;