Qlabel marquee text display

Effect display :

The whole function is optimized and modified on the basis of predecessors

One important point is ：
When windows The system sets the text display scale to be not 100% When , Setting the font size number here does not mean that the pixel size of the text is this number

The point is this 3 A function ：

// Adaptive function , Judge label Whether the text needs to scroll 
void upateLabelRollingState();
// Format text font 
void setScrollLabelFont(const QString &family, int pointSize = -1, int weight = -1, bool italic = false);
//  Force the running light on , All text scrolls 
void setFixedScrollShow(bool isOn);

Source program submission
The header file :

#ifndef SCROLL_LABEL_H
#define SCROLL_LABEL_H


#include <QDebug>
#include <QLabel>
#include <QTimerEvent>
#include <QPaintEvent>
#include <QTextDocument> // For judging rich text 
#include <QPainter>

//  Inherited from tag , After the qt Right click inside the designer to select " promote "  Make this inherited class control the corresponding labels that need to be scrolled 
class ScrollLabel :public QLabel
{
    
    Q_OBJECT
public:
    explicit ScrollLabel(QWidget *parent = nullptr);
    ~ScrollLabel();

    // Adaptive function , Judge label Whether the text needs to scroll 
    void upateLabelRollingState();
    // Format text font 
    void setScrollLabelFont(const QString &family, int pointSize = -1, int weight = -1, bool italic = false);
    //  Force the running light on , All text scrolls 
    void setFixedScrollShow(bool isOn);
public slots:
    // Change the displacement regularly , Change to the beginning at the end   Responsible for modifying the current pixel displacement value left startTimer Start ,killTimer end 
    void timerEvent(QTimerEvent *e) Q_DECL_OVERRIDE;

    // Redraw events , According to the displacement left Show text 
    void paintEvent(QPaintEvent *e) Q_DECL_OVERRIDE;

    // Setting text in 、 The scaling event calls the adaptive function twice 
    void setText(const QString &txt);

    // Set pictures , Mainly lt Set back 0, Make it return to normal picture display 
    void setPixmap(const QPixmap &pix);

    // Window change event 
    void resizeEvent(QResizeEvent *e) Q_DECL_OVERRIDE;

    //  According to the given value , Modify the scrolling speed  sp Is how many pixels to scroll at a time ,st How many seconds trigger a scroll 
    void setspeed(int sp=10,int st=300);

private:
    int timerId; // Timer id
    int text_wpixel; // Stored current label The pixel horizontal length of the inner string 

    int speedt;//  How often is scrolling triggered 
    int spixel;//  How many pixels to scroll at a time 

    int left;//  Indicates the current pixel scrolling amount 

    QString blank;// Space 
    int blank_wp;// The pixel width of the space 

    int start_scroll;

    uint8_t flag; // Determine whether scrolling should be enabled  0 no  1 really 

    bool isFixedScroll;
};

#endif // SCROLL_LABEL_H

cpp file ：
#include “scrolllabel.h”

ScrollLabel::ScrollLabel(QWidget *parent):QLabel(parent)
{
    
    timerId = -1;//  Timer ID
    text_wpixel = 0; // The pixel length of the text 

    speedt = 80;//  How often is scrolling triggered 
    spixel = 10;//  How many pixels to scroll at a time 

    //start_scroll = this->width();// Saved the initial width of the form , Avoid window changes without scrolling 

    flag = 0;// Default not to handle 

    isFixedScroll = false; // By default, it scrolls when the text is too long 
}

ScrollLabel::~ScrollLabel()
{
    
    if(timerId >= 0)
        killTimer(timerId);
}

// Setting text in 、 The scaling event calls the adaptive function twice 
void ScrollLabel::setText(const QString &txt)
{
    
    if(Qt::mightBeRichText(txt))// Determine whether it is rich text 
        flag = 0;  //0 Don't deal with , Directly display with the original painting event , Use this when it belongs to rich text  1 Left to right  2 Up and down 
    else
        flag = 1;

    QLabel::setText(txt);
    upateLabelRollingState();
}

// Set pictures , Mainly lt Set back 0, Make it return to normal picture display 
void ScrollLabel::setPixmap(const QPixmap &pix)
{
    
    flag=0;
    QLabel::setPixmap(pix);
}

// Window change event 
void ScrollLabel::resizeEvent(QResizeEvent *e)
{
    
    QLabel::resizeEvent(e);
    upateLabelRollingState();
}

//  According to the given value , Modify the scrolling speed  sp Is how many pixels to scroll at a time ,st How many seconds trigger a scroll 
void ScrollLabel::setspeed(int sp,int st)
{
    
    spixel = sp;
    speedt = st;

    upateLabelRollingState(); //　 Refresh the scrolling amount once 
}

// Used to determine label Whether the text needs to scroll , Is the core of this function 
void ScrollLabel::upateLabelRollingState()
{
    
    // Get text size , Less than the length of the text box , No scrolling required 
    QFont ft = font();//  Get the format of the current font , There are text size and text pixel size 
    QFontMetrics fm(ft); //  Based on the current font format 

    #if QT_VERSION > QT_VERSION_CHECK(5,11,0)// According to the official documentation ,5.11 Then use the new function 
    text_wpixel = fm.horizontalAdvance(text() ); // Based on the current font format , Calculate the pixel width of the font 
    #else
    text_wpixel = fm.width(text() ); // Based on the current font format , Calculate the pixel width of the font 
    #endif

    if((flag == 1 && isFixedScroll) || ((text_wpixel > this->width() ) && flag == 1) )// ** The length or height exceeds itself label The pixel size of , Turn on scrolling *** Key judgments 
    {
    
        left = 0; //  Marks the current pixel scrolling amount 

        #if QT_VERSION > QT_VERSION_CHECK(5,11,0)// According to the official documentation ,5.11 Then use the new function 
        blank = " ";// Space 
        blank_wp = fm.horizontalAdvance(blank );// The pixel width of the space , It is convenient to calculate whether the end is reached later 
        #else
        blank = " ";// Space 
        blank_wp = fm.width(blank );// The pixel width of the space 
        #endif

        qDebug()<< "OK!";

        // Turn on timer , The timer triggers the scrolling effect at a fixed time 
        timerId = startTimer(speedt);

    }
    else// Turn off text box scrolling 
    {
    
        qDebug()<< "no OK!";
        flag = 0; // close 
        if(timerId >= 0){
    
            killTimer(timerId);
            timerId = -1;
        }
    }

}

void ScrollLabel::setScrollLabelFont(const QString &family, int pointSize, int weight, bool italic)
{
    
    QFont f(family,pointSize,weight,italic); // When windows The system sets the text display scale to be not 100% When , Setting the font size number here does not mean that the pixel size of the text is this number 
    f.setPixelSize(pointSize);
    setFont(f);
}

void ScrollLabel::setFixedScrollShow(bool isOn)
{
    
    isFixedScroll = isOn;
}

// Change the displacement regularly , Change to the beginning at the end   Responsible for modifying the current pixel displacement value 
void ScrollLabel::timerEvent(QTimerEvent *e)
{
    
    if(e->timerId() == timerId && isVisible())
    {
    
        left += spixel;// (0,0) In the upper left corner , Increase the corresponding pixels each time 
        if((left + 20) > (text_wpixel + blank_wp) )//  It means to the end 
        {
    
            left = 1-( this->width() ); // To add , Negative numbers mean starting from the far right 
        }

        //repaint();// Immediately trigger a refresh , No redundancy , But it consumes performance 
        update();// It won't refresh immediately , There may be event redundancy , But save performance 
        //update and repaint The difference between , Please have a look at QT documentation 
    }

    QLabel::timerEvent(e);
}

// Redraw events , According to the displacement left Show text 
void ScrollLabel::paintEvent(QPaintEvent *e)
{
    
    if(flag == 0){
     //　 Don't deal with , Call the default function of the tag directly 
        QLabel::paintEvent(e);
        return;
    }

    QPainter pen(this);
    //  Get current label Rectangle size of 
    QRect rc = rect();
    rc.setHeight(rc.height() /*- 2*/);
    rc.setWidth(rc.width() /*- 2*/);

    QString strText = blank + text();
    rc.setLeft(rc.left() - left); // Modify rectangle  x Axis ,  because left It's getting bigger ,setLeft It's getting smaller ,(0,0) In the upper left corner , Fixed left shift 
    pen.drawText(rc,Qt::AlignVCenter, strText);// According to the given rectangular coordinates , Draw labels 
}