QTextDocument Block Boundary QRegExp

Matching over Block boundaries using QRegExp on QTextDocument

(formerly known as QTextDocument-Line-ending-and-Advanced-regular-expression-support)

Experimental

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

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

.*

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 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 <b>.*</b> and its minimal and case switches set.

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