Mouse Pointer and Label Background Coloring in Qt Application with Multiple Labels

JoeCFD

void HandLabel::mousePressEvent(QMouseEvent *event)
{
    Q_UNUSED(event);

    QPalette pal = palette();
    QColor selectedColor = pal.color(QPalette::Window);

    if (m_bgColor == selectedColor) {
        pal.setColor(QPalette::Window, Qt::transparent);
    } else {
        pal.setColor(QPalette::Window, m_bgColor);
    }
    setPalette(pal);

   /* something like this */
   QLabel::mousePressEvent( event );
}

SGaist

@Collaxd you better go with a good old fashioned cpp tutorial about that very subject.

Collaxd

@Christian-Ehrlicher
Thank you, friends. I really didn't mean to offend when I mentioned the chat. In fact, I'm just a veterinarian enthusiast in programming trying to learn some things. I'll do more research.

JonB

@Collaxd
No offence taken.

In, say, your HandLabel::enterEvent() overridden method you call

QLabel::enterEvent(event); // chama o enterEvent da classe base

Same for leaveEvent(). It allows whatever the class you derive from to see these events and act on them, as well as your own code.

I would guess you need to do the same for your HandLabel::mousePressEvent(). I would let it call QLabel::mousePressEvent(event), as well as your code. Maybe also for mouseMoveEvent(). Does that help with your

When I click on a label, the mouse pointer becomes stuck on that label, and I am unable to click on other nearby labels.

?

Collaxd

@JonB
Perfect, thanks for your understanding and help, but even when calling the base event, the mouse is still 'stuck' on the initial click label, I can do something just with enter, it also serves my purpose, but it doesn't work in the same way

Here's an example of how my code is and an app I want to 'imitate' with it working

#include "HandLabel.h"

#include <qapplication.h>

HandLabel::HandLabel(const QString &text, QWidget *parent, Qt::WindowFlags f)
    : QLabel(text, parent, f)
{
    setAlignment(Qt::AlignCenter);
    setFrameStyle(QFrame::Panel | QFrame::Sunken);
    setAutoFillBackground(true);
}


void HandLabel::onbgColorChanged(QColor newColor)
{
    setBgColor(newColor);
}

void HandLabel::mousePressEvent(QMouseEvent *event)
{
    QLabel::mousePressEvent(event); // chama o mousePressEvent da classe base

    if (event->buttons() & Qt::LeftButton)
        updateBackground();

}

void HandLabel::mouseMoveEvent(QMouseEvent *event)
{
    QLabel::mouseMoveEvent(event);

    qDebug() << event;
//    updateBackground();

}

void HandLabel::enterEvent(QEnterEvent *event)
{
    QLabel::enterEvent(event); // chama o enterEvent da classe base
    updateBackground();
    setMouseTracking(true);
}

void HandLabel::leaveEvent(QEvent *event)
{
    QLabel::leaveEvent(event); // chama o leaveEvent da classe base
    // emite um evento mouseReleaseEvent
    setMouseTracking(false);
}

void HandLabel::updateBackground()
{
    QPalette pal = palette();
    QColor selectedColor = pal.color(QPalette::Window);
    if (m_bgColor == selectedColor)
        pal.setColor(QPalette::Window, Qt::transparent);
    else
        pal.setColor(QPalette::Window, m_bgColor);

    setPalette(pal);
}


QColor HandLabel::bgColor() const
{
    return m_bgColor;
}

void HandLabel::setBgColor(const QColor &newBgColor)
{
    m_bgColor = newBgColor;
}

alt text

mpergand

@Collaxd said in Mouse Pointer and Label Background Coloring in Qt Application with Multiple Labels:

he mouse is still 'stuck' on the initial click label,

I think you should use dragEnterEvent & dragMoveEvent instead of enterEvent, if you want to select muti objects while mouse press.

Collaxd

@mpergand

void HandLabel::dragEnterEvent(QDragEnterEvent *event)
{
    qDebug() << event;
    QLabel::dragEnterEvent(event);
}

void HandLabel::dragMoveEvent(QDragMoveEvent *event)
{
    qDebug() << event;
    QLabel::dragMoveEvent(event);
}

Thanks for your help, but it doesn't appear in the debug when I add the two functions :(

I managed to do something similar in React + JS but I put the lstenner in the parent layout which is not possible here since the parent layout is a grid and has no mouse properties

mpergand

@Collaxd
Seems to work:

class Label : public QLabel
{
    public:
    Label(const QString& text, QWidget* parent=nullptr) : QLabel(text,parent)
    {
    setFrameStyle(QFrame::Panel | QFrame::Sunken);
    setAcceptDrops(true);
    }

    void mousePressEvent(QMouseEvent *ev) override
    {
         qDebug()<<Q_FUNC_INFO;
         QLabel::mousePressEvent(ev);
    }

    void mouseMoveEvent(QMouseEvent *ev) override
    {
         qDebug()<<Q_FUNC_INFO;
        QDrag *drag = new QDrag(this);
        QMimeData *mimeData = new QMimeData;

        mimeData->setText("");
        drag->setMimeData(mimeData);

        Qt::DropAction dropAction = drag->exec(Qt::MoveAction);
        if(  dropAction == Qt::IgnoreAction )
        {
            qDebug()<<"end drag";
            drag->deleteLater();
        }
    }


    void dragEnterEvent(QDragEnterEvent* ev ) override
    {
        qDebug()<<Q_FUNC_INFO;
         ev->acceptProposedAction();
    }

    void dragMoveEvent(QDragMoveEvent* ev ) override
    {
        qDebug()<<Q_FUNC_INFO<<ev->source()<<this;

    }
};

Each Label receives dragMoveEvent when the mouse is over.
Looks promising, have a look at the doc about drag&drop:
https://doc.qt.io/qt-5/dnd.html

Collaxd

@mpergand
I would like to thank you very much for your solution, it was a success! I've been searching for days and couldn't find anything similar, which generated a lot of learning and made me realize that I still have a lot to study!

For future readers, here is the solution:

void HandLabel::mouseMoveEvent(QMouseEvent *event)
{
    Q_UNUSED(event);

    QDrag *drag = new QDrag(this);

    QMimeData *mimeData = new QMimeData;
    drag->setMimeData(mimeData);

    Qt::DropAction dropAction = drag->exec(Qt::MoveAction);
    if(  dropAction == Qt::IgnoreAction ) {
        drag->deleteLater();
    }
}

void HandLabel::dragEnterEvent(QDragEnterEvent *event)
{
    Q_UNUSED(event);
    updateColorScheme();
}

Despite the mouse having a 'block' symbol, the colors are working perfectly!

alt text

mpergand

@Collaxd said in Mouse Pointer and Label Background Coloring in Qt Application with Multiple Labels:

void HandLabel::dragEnterEvent(QDragEnterEvent *event)
{
Q_UNUSED(event);
updateColorScheme();
}

Oh, miss that drag enter is call for each label !
Even easier that I imagined.

Despite the mouse having a 'block' symbol, the colors are working perfectly!

You need to call ev->acceptProposedAction();
for that symbol to not appear.