Displaying a tooltip when mouse hovers over part of Widget

Perdrix

I have a widget subclass that displays an image in part of its real-estate.

When the mouse hovers over the image I want to display a tooltip, but only if it is in that part of the widget that contains the image, so QWidget::setToolTip() isn't perfect for the job - though I can use that as a fall back solution.

I already have handlers in place for mousePressEvent, mouseMoveEvent, and mouseReleaseEvent.

I tried to find hoverEnterEvent and hoverLeaveEvent for QWidget, but AFAICT these don't exist.

What's the best way to handle this please?

Perdrix

So the trick is to capture the QEvent::ToolTip event in event() and invoke showText on the relevant rectangle? Is that right?

Here's what I did:

bool DSSImageView::event(QEvent* event)
{
    if (QEvent::ToolTip == event->type())
    {
        // 
        // Create a rectangle representing the image area
        //
        QRect rect(m_origin.x(), m_origin.y(), (m_pixmap.width() * m_scale), (m_pixmap.height() * m_scale));

        //
        // Get the tooltip text if any and if the mouse is over the image, show the tooltip
        //
        const QString tip = toolTip();
        if (!tip.isEmpty())
        {
            const QPoint mouseLocation(QCursor::pos());

            QToolTip::showText(mouseLocation, tip, this, rect);
        }
        return true;
    }
    // Make sure the rest of events are handled
    return Inherited::event(event);
}

but the tooltip was displayed regardless of where in the widget the mouse was (IOW, not just in rect { x = 0, y = 83, width = 500, height = 333 } almost as if I'd called the version of showText that didn't use rect).

So it would seem that there's a bug in QToolTip::showText(const QPoint &pos, const QString &text, QWidget *w, const QRect &rect)

The following code does work:

bool DSSImageView::event(QEvent* event)
{
    if (QEvent::ToolTip == event->type())
    {
        //
        // If the mouse is over the image, but not over the toolbar,
        // get the tooltip text and if there is any, display it
        //
        const QPoint globalMouseLocation(QCursor::pos());
        const QPointF mouseLocation(mapFromGlobal(globalMouseLocation));
        if (mouseOverImage(mouseLocation) && !m_pToolBar->underMouse())
        {
            const QString tip = toolTip();
            if (!tip.isEmpty())
            {
                QToolTip::showText(globalMouseLocation, tip, this);
            }
        }
        return true;
    }
    // Make sure the rest of events are handled
    return Inherited::event(event);
}

jsulm

@Perdrix You can specify where to show a tooltip: https://doc.qt.io/qt-5/qtooltip.html#showText

Perdrix

This post is deleted!

Perdrix

So the trick is to capture the QEvent::ToolTip event in event() and invoke showText on the relevant rectangle? Is that right?

Here's what I did:

bool DSSImageView::event(QEvent* event)
{
    if (QEvent::ToolTip == event->type())
    {
        // 
        // Create a rectangle representing the image area
        //
        QRect rect(m_origin.x(), m_origin.y(), (m_pixmap.width() * m_scale), (m_pixmap.height() * m_scale));

        //
        // Get the tooltip text if any and if the mouse is over the image, show the tooltip
        //
        const QString tip = toolTip();
        if (!tip.isEmpty())
        {
            const QPoint mouseLocation(QCursor::pos());

            QToolTip::showText(mouseLocation, tip, this, rect);
        }
        return true;
    }
    // Make sure the rest of events are handled
    return Inherited::event(event);
}

but the tooltip was displayed regardless of where in the widget the mouse was (IOW, not just in rect { x = 0, y = 83, width = 500, height = 333 } almost as if I'd called the version of showText that didn't use rect).

So it would seem that there's a bug in QToolTip::showText(const QPoint &pos, const QString &text, QWidget *w, const QRect &rect)

The following code does work:

bool DSSImageView::event(QEvent* event)
{
    if (QEvent::ToolTip == event->type())
    {
        //
        // If the mouse is over the image, but not over the toolbar,
        // get the tooltip text and if there is any, display it
        //
        const QPoint globalMouseLocation(QCursor::pos());
        const QPointF mouseLocation(mapFromGlobal(globalMouseLocation));
        if (mouseOverImage(mouseLocation) && !m_pToolBar->underMouse())
        {
            const QString tip = toolTip();
            if (!tip.isEmpty())
            {
                QToolTip::showText(globalMouseLocation, tip, this);
            }
        }
        return true;
    }
    // Make sure the rest of events are handled
    return Inherited::event(event);
}