Add a ToolTip with a QSyntaxHighlighter and a QTextCharFormat

Question

I'm trying to create a little syntax highlighter in Qt, and i want to show a tooltip with the description of the error when the user hoover it.

(I'm subclassing QSyntaxHighlighter)

I've tried the QTextCharFormat::setToolTip function, but it didn't work :/ The text is red-underlined as expected, but no tooltip are shown when I hover over it.

Did i miss something ? Or should i use another method ?

void CodeHighlighter::highlightBlock(const QString &text)
{
    _errorFormat.setProperty(QTextFormat::TextUnderlineStyle, QTextCharFormat::SpellCheckUnderline);
    _errorFormat.setProperty(QTextFormat::TextUnderlineColor, QColor(Qt::red));
    if (!isLineValid(text.toStdString())) {

        // The following line does not work !
        _errorFormat.setToolTip(QString::fromStdString(getLastError()));

        setFormat(0, text.length(), _errorFormat);
    }
    for (const HighlightingRule &rule : qAsConst(_highlightingRules)) {
        QRegularExpressionMatchIterator matchIterator = rule.pattern.globalMatch(text);
        while (matchIterator.hasNext()) {
            QRegularExpressionMatch match = matchIterator.next();
            QTextCharFormat format = this->format(match.capturedStart());
            format.merge(rule.format);
            setFormat(match.capturedStart(), match.capturedLength(), format);
        }
    }
}

Have you seen bug report [QTBUG-21553](https://bugreports.qt.io/browse/QTBUG-21553)? — PiCTo, Dec 03 '19 at 19:04
Yes, thats exactly my problem, is this bug still not fixed in Qt5.12.5 ? If it's the case, what should i do to have my tooltips working ? — Azyrod, Dec 03 '19 at 20:59
@Azyrod I recommend that you report it again since, as they indicate in the comments, the follow-up was not done because the one who reported did not give the necessary feedback. — eyllanesc, Dec 03 '19 at 22:58
Created a new bug report (https://bugreports.qt.io/browse/QTBUG-80524), let's see if it get fixed.... — Azyrod, Dec 04 '19 at 09:18
QT hasn't implemented it yet, I believe it might come with future versions. Ref: https://code.woboq.org/qt5/qtbase/src/gui/text/qtextodfwriter.cpp.html#751 — Folling, Jan 21 '20 at 11:26

ssokolow · Accepted Answer · 2023-05-08T18:04:16.500

You can make it work by overriding handling of the QEvent::ToolTip and doing the lookup yourself.

I don't have time to rewrite my complete answer in C++, but:

This SO answer has C++ code for doing the override but not the lookup. (Basically, on the QTextEdit or QPlainTextEdit, you setMouseTracking(True), override the event method, and hand off to the default implementation unless event->type() == QEvent::ToolTip. The other answer to that question points out that you'll also need to correct for margins if you're using them.)
This QtCenter post has C++ code to look up the highlighter-applied format in C++... though it does use one deprecated method. (The gist of it is that, in modern Qt, you need to use cursorForPosition, then .block().layout()->formats() and iterate through, comparing offsets to the cursor's position(). additionalFormats() being the deprecated method and formats() being the modern one.)
This SO answer I wrote is a complete, runnable example which demonstrates exposing grammar-checking information as tooltips... it's just written in Python against PyQt.

Add a ToolTip with a QSyntaxHighlighter and a QTextCharFormat

1 Answers1