PyQt4 4.4.4 : a bug with highlightBlock ?

[Snouffy]

Hello everybody,

I've been trying to do some syntax highlighting using PyQt4. I ported
the example given in the documentation of Qt4 to Python. It works fine
on my computer at work (which has PyQt4 version 4.3.3) but doesn't on
my home computer (which has version 4.4.4) : it gets stuck in an
infinite loop.
Here is the code :

class MyHighlighter(QtGui.QSyntaxHighlighter):
def __init__(self, edit):
QtGui.QSyntaxHighlighter.__init__(self,edit)

def highlightBlock(self, text):
myClassFormat = QtGui.QTextCharFormat()
myClassFormat.setFontWeight(QtGui.QFont.Bold)
myClassFormat.setForeground(QtCore.Qt.darkMagenta)
pattern = "\\b[A-Z_]+\\b"

expression = QtCore.QRegExp(pattern)
index = text.indexOf(expression);
while (index >= 0):
length = expression.matchedLength()
self.setFormat(index, length, myClassFormat)
index = text.indexOf(expression, index + length)

What am I missing ? Is this a known bug of version 4.4.4 ?

Thank you,

Alexis.

[David Boddie]

On Wednesday 18 November 2009 11:47, Snouffy wrote:

> I've been trying to do some syntax highlighting using PyQt4. I ported
> the example given in the documentation of Qt4 to Python. It works fine
> on my computer at work (which has PyQt4 version 4.3.3) but doesn't on
> my home computer (which has version 4.4.4) : it gets stuck in an
> infinite loop.

This is a known issue. There are examples distributed with PyQt that should
have been updated to use a slightly different approach.

> Here is the code :
>
> class MyHighlighter(QtGui.QSyntaxHighlighter):
> def __init__(self, edit):
> QtGui.QSyntaxHighlighter.__init__(self,edit)
>
> def highlightBlock(self, text):
> myClassFormat = QtGui.QTextCharFormat()
> myClassFormat.setFontWeight(QtGui.QFont.Bold)
> myClassFormat.setForeground(QtCore.Qt.darkMagenta)
> pattern = "\\b[A-Z_]+\\b"
>
> expression = QtCore.QRegExp(pattern)
> index = text.indexOf(expression);
> while (index >= 0):
> length = expression.matchedLength()
> self.setFormat(index, length, myClassFormat)
> index = text.indexOf(expression, index + length)

You need to change the indexOf() calls to indexIn() calls on the QRegExp
object:

index = expression.indexIn(text, index + length)

> What am I missing ? Is this a known bug of version 4.4.4 ?

I think there was a behavioural change at some point that affected regular
expression searching in QStrings.

David

[Snouffy]

> You need to change the indexOf() calls to indexIn() calls on the QRegExp
> object:
>
>   index = expression.indexIn(text, index + length)

Thank you so much ! After looking a bit more I found out that when
using indexOf the command :
length = expression.matchedLength()
was the one causing a problem. Thus I also had to change the line :
index = text.indexOf(expression)
to :
index = expression.indexIn(text)

Now it works like a charm ! I'll test it at work where we have PyQt
4.3.3.

Thanks again !