Qt 6 crash in QPlainText::setExtraSelections after QPlainText::setDocument

Question

I'm trying to set up a text widget that highlights the searched word, when I open a new file with QPlainText::setDocument, then immediately use QPlainText::setExtraSelections I get a SIGSEV crash in:

QTextDocumentPrivate::rootFrame
QTextDocumentPrivate::frameAt
QTextCursorPrivate::complexSelectionTable
QTextCursor::hasComplexSelection
QWidgetTextControl::selectionRect
QWidgetTextControl::setExtraSelections

QTextDocumentPrivate is causing a SIGSEV because it is a null this pointer. But this doesn't happen if no word is set before the document is loaded.

I must be supposed to do something to force it to generate the QTextDocumentPrivate. But I have no idea what that is.

Answer 1

Actually, this happens because QPlainText::setDocument does not remove the prior results of QPlainText::setExtraSelections. So when setting the new selections tries to remove the previous things selected, they all have invalid pointers and that causes the crash.

To fix it call: textEdit->setExtraSelections({}); to clear out the selections prior to calling QPlainText::setDocument.