View source for QTextDocument Block Boundary QRegExp

== Matching over Block boundaries using QRegExp on QTextDocument == 
:(formerly known as QTextDocument-Line-ending-and-Advanced-regular-expression-support)
{{WarningBox | text=Experimental}}

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

The {{DocLinkRef | ref=QTextDocument | anchor=find-2 | label=QTextDocument::find(QRegExp)}} method will not attempt to match across a ''block boundary''. As a result, although the {{DocLink | QRegExp}} doc says that is matched by '''.*''' and by '''\s''', one can never get a match to in a {{DocLink | QPlainTextEdit}} document. The '''\n''' is end of block and the search never spans a block. Thus it seems impossible for a pattern like

<code>.*</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 {{DocLink | QTextDocument}}. '''QRegExp''' does perform as documented when it is applied to a {{DocLink | QString}}. So the following code can apply a general '''QRegExp''' 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 '''''<nowiki><b>.*</b></nowiki>''''' 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

range_tc.setPosition(start_tc.selectionStart(),QTextCursor.KeepAnchor) # select text between start and end cursor
hit_pos = qrxp.indexIn(range_tc.selectedText()) # apply regexp to (part of) the document as a QString

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>