View source for QTextDocument-Line-ending-and-Advanced-regular-expression-support

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= QTextDocument Line Endings and Advanced RegExp =
== Warning: Experimental Info ==

I've picked from QtForum itself. It's progressive article. I will update more when I will achieve something.

The find(regex) method of QTextDocument will not attempt to match across a “block” boundary (see answers in this post [developer.qt.nokia.com]). As a result, although the QRegExp doc says that is matched by .* and by , one can never get a match to in a QPlainTextEdit document. The is end of block and the search never spans a block. Thus it seems impossible for a pattern like


<code><b>.*</b></code>


to find a match when the markup begins on one line and ends on another.

There is a way around this. The restriction is in QTextDocument; QRegExp does perform as documented when it is applied to a QString. So the following code can apply a general regex to a document. This is using PyQt4; the translation to C++ should be clear. Given is a QPlainTextEdit qpte whose cursor is the starting point for the search. Also given is a QRegExp qrxp that has been prepared with a search pattern such as “<b>.*</b>” and its minimal and case switches set.

<code>
 start_tc = qpte.textCursor() # cursor with starting position
 range_tc = QTextCursor(start_tc) # make a copy linked to same doc
 range_tc.movePosition(QTextCursor.End) # point to end of doc
 # set cursor to select all text from starting point to end
 range_tc.setPosition(start_tc.selectionStart(),QTextCursor.KeepAnchor)
 # apply regexp to (part of) the document as a QString
 hit_pos = qrxp.indexIn(range_tc.selectedText())
 if hit_pos > –1 : # first occurrence at hit_pos offset
 find_tc = QTextCursor(start_tc) # another cursor
 find_tc.setPosition(start_tc.selectionStart()+hit_pos) # point to hit
 find_tc.movePosition(QTextCursor.Right,
 QTextCursor.KeepAnchor,
 qrxp.matchedLength()) # select matched text
 qpte.setTextCursor(find_tc) # match visible to user<code>

</code>