Crazy QPlainTextEdit::document() behavior

[Lykurg]

Hi,

I have following class (simplified...):

class MyLabel : public QLabel
{
    Q_OBJECT
  public:
    explicit MyLabel(QWidget *parent = 0, Qt::WindowFlags f = 0);
 
  protected:
    void paintEvent(QPaintEvent *event);
 
  private:
    QPlainTextEdit *m_doc; //it is hidden, only for storing reason.
};

class MyLabel : public QLabel
{
    Q_OBJECT
  public:
    explicit MyLabel(QWidget *parent = 0, Qt::WindowFlags f = 0);

  protected:
    void paintEvent(QPaintEvent *event);

  private:
    QPlainTextEdit *m_doc; //it is hidden, only for storing reason.
};

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So assume there is some content in the text edit and I do this:

void MyLabel::paintEvent(QPaintEvent *event)
{
  Q_UNUSED(event);
  QPainter p(this);
  m_doc->document()->setPageSize(rect().size());
  m_doc->document()->drawContents(&p, rect());
}

void MyLabel::paintEvent(QPaintEvent *event)
{
  Q_UNUSED(event);
  QPainter p(this);
  m_doc->document()->setPageSize(rect().size());
  m_doc->document()->drawContents(&p, rect());
}

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nothing is shown, but when I have this:

void MyLabel::paintEvent(QPaintEvent *event)
{
  Q_UNUSED(event);
  QPainter p(this);
  QTextDocument *d = m_doc->document()->clone();
  d->setPageSize(rect().size());
  d->drawContents(&p, rect());
  d->deleteLater();
}

void MyLabel::paintEvent(QPaintEvent *event)
{
  Q_UNUSED(event);
  QPainter p(this);
  QTextDocument *d = m_doc->document()->clone();
  d->setPageSize(rect().size());
  d->drawContents(&p, rect());
  d->deleteLater();
}

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everything is painted well. But why I have to clone the document??? That's not very performant... What might be the reason why I am not able to use QPlainTextEdit::document() directly?

Thanks

[toutarrive]

Maybe this link could be useful to you.
http://www.mail-archive.com/pyqt@riv.../msg19787.html

excerpt :

And yet in the latter case, drawContents() renders nothing at all. Cursory
investigation points to a different QAbstractTextDocumentLayout implementation
under the hood depending on the TextEdit flavor in use.

[Lykurg]

Ok thanks, that is really strange. But I feel better now, that I am not the only one having that trouble...

[wysota]

Why don't you use QTextDocument directly? What do you need QPlainTextEdit for?

[Lykurg]

Why don't you use QTextDocument directly? What do you need QPlainTextEdit for?

Today I figured out that my way wont work - beside that issue So I don't need it any more but I have had to use QPlainTextEdit since I need the functionality of getting the underlaying word at a specific point (mousepress) and therefore QPlainTextEdit::cursorForPosition() was perfect.

So for future: Do you know such a feature (QPoint -> QTextCursor) with QTextDocument?

[wysota]

QTextDocument has a layout which has a QAbstractTextDocumentLayout::hitTest() method that returns a position in the document based on coordinates. Knowing the position you can create a QTextCursor and use QTextCursor::setPosition() to position the cursor in appropriate place so that you can fetch the word underneath.

[Lykurg]

Great! Thanks a lot. Haven't know about the hitTest() function.

[wysota]

Until I had a look at the docs today, I have been unaware of it as well "Use the docs, Luke... use the docs..."

[Lykurg]

"Use the docs, Luke... use the docs..."

Unfortunately my name is not Luke.
Yeah, ok, temporary - hope so - incompetence...