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qttextscrollqwidget
New Moon
New Moon

Reputation: 817

Qt - Scrolling the Text in QWidget

I'm newbie to Qt. Now I'm learning about Scrolling the Text in a QWidget. When my text size is lesser than the Widget then the text should scroll only once till it reaches the end (text is moved from right to left). once it reaches the left end then again it should start from the right end. plz help me to do this... Thanks in advance..

Upvotes: 2

Views: 9012

Answers (3)

New Moon
New Moon

Reputation: 817

*Here is my Coding....*

**ScrollText.h**

#ifndef SCROLLTEXT_H
#define SCROLLTEXT_H

#include <QWidget>
#include <QStaticText>
#include <QTimer>

class ScrollText : public QWidget
{
    Q_OBJECT
    Q_PROPERTY(QString text READ text WRITE setText)
    Q_PROPERTY(QString separator READ separator WRITE setSeparator)

public:
    explicit ScrollText(QWidget *parent = 0);

public slots:
    QString text() const;
    void setText(QString text);

    QString separator() const;
    void setSeparator(QString separator);

protected:
    void paintEvent(QPaintEvent *);

private:
    void updateText();
    QString _text;
    QString _separator;
    QStaticText staticText;
    int singleTextWidth;
    QSize wholeTextSize;
    int leftMargin;
    int scrollPos;
    QImage buffer;
    QTimer timer;

private slots:
    virtual void timer_timeout();
};

#endif // SCROLLTEXT_H


**ScrollText.cpp**

#include "Widget.h"
#include <QPainter>
#include <QDebug>

ScrollText::ScrollText(QWidget *parent) :
    QWidget(parent), scrollPos(0)
{
    staticText.setTextFormat(Qt::PlainText);
    setFixedHeight(fontMetrics().height());
    leftMargin = width();
    setSeparator("   ");
    connect(&timer, SIGNAL(timeout()), this, SLOT(timer_timeout()));
    timer.setInterval(30);
}

QString ScrollText::text() const
{
    return _text;
}

void ScrollText::setText(QString text)
{
    _text = text;
    updateText();
    update();
}

QString ScrollText::separator() const
{
    return _separator;
}

void ScrollText::setSeparator(QString separator)
{
    _separator = separator;
    updateText();
    update();
}

void ScrollText::updateText()
{
    singleTextWidth =  fontMetrics().width(_text);
    timer.start();
    scrollPos = 0;
    staticText.setText(_text + _separator);
    staticText.prepare(QTransform(), font());
    wholeTextSize = QSize(fontMetrics().width(staticText.text()), fontMetrics().height());
    timer.stop();
}

void ScrollText::paintEvent(QPaintEvent*)
{
    QPainter painter(this);
    buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);

    buffer.fill(qRgba(0, 0 ,0, 0));
    QPainter pb(&buffer);
    pb.setPen(painter.pen());
    pb.setFont(painter.font());

    int x = qMin(-scrollPos, 0)+ leftMargin + (leftMargin/2);

    if(x < width())
    {
        pb.drawStaticText(QPointF(x, (height() - wholeTextSize.height()) / 2) + QPoint(0,0), staticText);
        x +=  wholeTextSize.width();

        if(x < 0)
        {
            scrollPos = 0;
        }

        painter.drawImage(0, 0, buffer);
    }
}

void ScrollText::timer_timeout()
{
    scrollPos = (scrollPos+ 2);
    update();
}

Upvotes: 2

Eric Hulser
Eric Hulser

Reputation: 4022

So, the question is a bit confusing. It sounds like what you need is more about how to setup a right-to-left word wrap right?

If this is the case, use a QLabel, set its QWidget::layoutDirection property to RightToLeft vs. the default LeftToRight, and set its QLabel::wordWrap property to True.

Upvotes: 0

Silas Parker
Silas Parker

Reputation: 8147

I can think of two ways to do this, the easy way, and the hard way.

Easy way:

Put a QLabel in a QScrollArea and scroll the area around, could be controlled by a QTimer.

Hard way:

Create a custom QWidget that scrolls text in its paintEvent. The benefit of this would be more control over the rendering, and possibly lower resource usage.

Upvotes: 0

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