Changing the color of a QTextBlock that is within a QTextDocument

Question

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.

Answer 1

Look at QSyntaxHighlighter http://doc.qt.io/qt-4.8/qsyntaxhighlighter.html

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

Answer 2

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?