Changing the color of a QTextBlock that is within a QTextDocument

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+1 Q:

Changing the color of a QTextBlock that is within a QTextDocument

Is there any other way to change the QTextLayout of a QTextBlock that is within a QTextDocument without having to subclass QAbstractTextDocumentLayout and call its documentChanged?

I know that on a call to QTextBlock::layout() const ; "the returned QTextLayout object can only be modified from the documentChanged implementation of a QAbstractTextDocumentLayout subclass" but I was wodering if there was any other way before I implemented it.

UPDATE basically I just want paragraphs(QTextBlock) that are longer than X characters to be highlighted and the rest to be normal.

+1 A:

Problem with changing block's layout directly is that it will inadvertently affect the layout of the currently active document layout (instance of the internal QAbstractTextDocumentLayout implementation) - it computes positions of QTextDocument elements only inside the documentChanged() and uses them whenever it needs to repaint or hit-test - so these things might get broken.

Can you elaborate on what you're trying to achieve?

2010-03-25 09:46:40

im trying to highlight paragraphs that are longer than 15 characters to indicate they are too long. I am also trying to do this inside a QPlainTextEditor object from a slot connected to either the cursorPositionChanged() or textChanged() signals. I have tried textCursor().block().blockFormat().setBackground(QBrush(Qt::yellow); textCursor().block().layout()->setFont(QFont("Helvetica [Cronyx]")); and textCursor().setBlockFormat(*blkFormat); all without success but I have received a post on another question that mentions using QTextEdit::mergeCurrentCharFormat() so im going to try it.

yan bellavance 2010-03-25 16:15:54

From what you are telling me though it might be safer to just use QAbstractTextDocumentLayout::documentChanged ( int position, int charsRemoved, int charsAdded ). The other question I asked is here:http://stackoverflow.com/questions/2512661/how-to-change-the-background-of-a-text-bloc-in-a-text-document-in-qt

yan bellavance 2010-03-25 16:21:16

+1 A:

Look at QSyntaxHighlighter http://doc.qt.nokia.com/4.6/qsyntaxhighlighter.html

This pretty much will let you do exactly what you're trying to do.

Brian Roach 2010-03-26 22:42:51

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Changing the color of a QTextBlock that is within a QTextDocument

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