`find()` to search for the newline character via QRegExp

[tamlok]

Is there any way to search the newline character \n in QTextEdit using its find(QRegExp) method?

BTW, searching this will hang the find() function:

QTextEdit *edit = new QTextEdit();
edit->find(QRegExp("$"));

Thanks!

[Gojir4]

@tamlok Hi,

Usually QTextEdit use the unicode character "Paragraph Separator", which is \u2029.

I have used this regex to find all new line in text edit content:

QRegularExpression("\u2029|\r\n|\r|\n")

Works fine for me.

[JonB]

@Gojir4
Is that really what you use in your C++ source code?? Those \r & \ns are going to be passed as literal carriage-returns/newlines to construct the regular expression, which to me is not a good idea at all.

Better surely (standard C++)

    QRegularExpression("\u2029|\\r\\n|\\r|\\n")

[Gojir4]

@JonB yep, you're right. Noob mistake. I dont know if this is an issue when use with QTextDocument based widget. But I will correct it in my code anyway. Thanks for pointing me this.

[tamlok]

@Gojir4 Thanks! Are you using the QTextEdit::find() interface? find() seems only have QRegExp overloaded prototype and QRegExp("\x2029") does not work. BTW, do you know why find(QRegExp("$")) will hang the application?

Thanks again!

[JonB]

@tamlok said in `find()` to search for the newline character via QRegExp:

QRegExp("\x2029")

But the example for you to copy was "\u2029". \x... will not work.

[tamlok]

@JonB From the doc, it says:

\xhhhh	Matches the Unicode character corresponding to the hexadecimal number hhhh (between 0x0000 and 0xFFFF).

\u2029 does not work, either.

[JonB]

@tamlok
Sorry, OK to the \x rather than the \u, I'm not a C++-er.

In that case, I presume your "does not work" means that you have checked the return result of your QTextEdit::find(QRegExp("\x2029")) and that's false, right? What makes you think your text even has a \x2029 anywhere in it? If it's not finding it, I presume it does not.

[Gojir4]

@tamlok said in `find()` to search for the newline character via QRegExp:

find() seems only have QRegExp overloaded prototype

You can specify a PatternSyntax like QRegExp::FixedString, QRegExp::Wildcard, if you don't want to use regular expression.

@tamlok said in `find()` to search for the newline character via QRegExp:

BTW, do you know why find(QRegExp("$")) will hang the application?

Not really. That's seems strange. But probably this pattern is not well supported by QRegExp. There are some limitations with this class. That's the reason QRegularExpression was added in Qt to replace QRegExp. Unfortunately only QRegExp is currently supported with QTextEdit::find().

[tamlok]

@Gojir4 said in `find()` to search for the newline character via QRegExp:

@tamlok said in `find()` to search for the newline character via QRegExp:

find() seems only have QRegExp overloaded prototype

You can specify a PatternSyntax like QRegExp::FixedString, QRegExp::Wildcard, if you don't want to use regular expression.

No, I do want to use QRegExp to search for the "Paragraph Separator". But it seems not work (QRegExp("\x2029")).

@tamlok said in `find()` to search for the newline character via QRegExp:

BTW, do you know why find(QRegExp("$")) will hang the application?

Not really. That's seems strange. But probably this pattern is not well supported by QRegExp. There are some limitations with this class. That's the reason QRegularExpression was added in Qt to replace QRegExp. Unfortunately only QRegExp is currently supported with QTextEdit::find().

Emm... Seems that I have nothing to do but handle the corner cases manually.

[tamlok]

@JonB said in `find()` to search for the newline character via QRegExp:

@tamlok
Sorry, OK to the \x rather than the \u, I'm not a C++-er.

In that case, I presume your "does not work" means that you have checked the return result of your QTextEdit::find(QRegExp("\x2029")) and that's false, right? What makes you think your text even has a \x2029 anywhere in it? If it's not finding it, I presume it does not.

I am sure the text will have \x2029 because I have multiple lines and paragraphs in QTextEdit, which surely has the "Paragraph Separator".

Anyway, it seems that QRegExp does not supoprt that well.

[JonB]

@tamlok
That \x pattern then is actually recognised by QRegExp. You do not just want to pass the C character, I think. So try: QTextEdit::find(QRegExp("\\x2029")) ?

Also read up the hidesousness of https://stackoverflow.com/questions/22838656/what-qstring-can-not-pass-a-qregexp-of-the-form-x00-xff

[VRonin]

I think you can use QTextCursor::move(QTextCursor::EndOfLine) as an alternative.

Are you using the QTextEdit::find() interface? find() seems only have QRegExp overloaded prototype

This will be solved in Qt 5.13 thanks to @SGaist: https://codereview.qt-project.org/224913/