折线图：

#ifndef LINE_CHART_H
#define LINE_CHART_H

#include <QWidget>
#include <QPainter>
#include "circle.h"
class line_chart : public QWidget
{
    Q_OBJECT
public:
    explicit line_chart(QWidget *parent = nullptr);
protected:
    void paintEvent(QPaintEvent *event) override;
private:
    QVector<int> h;
    int max,min,sum;
signals:

};

#endif // LINE_CHART_H

#include "line_chart.h"
#include <QDebug>
line_chart::line_chart(QWidget *parent) : QWidget(parent)
{
    sum=0;
    for(int i=0;i<30;i++)
    {
        if(i%5==0)h<<i;
        else{
            h<<0;
        }
    }

    //最大值，最小值
    for(int i=0;i<30;++i)
    {
        if(i==0){
            max=h.at(i);
            min=h.at(i);
        }
        else{
            if(max<h.at(i))max=h.at(i);
            if(min>h.at(i))min=h.at(i);
        }
        sum+=h.at(i);
    }
}

void line_chart::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform | QPainter::TextAntialiasing, true);

    //画背景
    painter.save();
    painter.setPen(Qt::NoPen);
    painter.setBrush(QBrush(QColor(255,255,255)));
    painter.drawRect(rect());
    painter.restore();
    //画横线
    painter.save();
    //确定条数
    //4,0:3
    //5,0:4
    int count=max-min-1;
    int x1,x2,y;
    x1=5;
    x2=width()-5;
    y=height()-10;
    int w=(height()-20)/count;
    QPen pen;
    pen.setColor(QColor(214, 223, 255));
    pen.setWidth(1);
    pen.setStyle(Qt::SolidLine);
    painter.setPen(pen);
    for(int i=0;i<count;++i)
    {
        painter.drawLine(x1,y,x2,y);
        y=y-w;
    }

    painter.restore();

    //画蓝色折线
    painter.save();
    double w1=width()-20;
    x1=10;
    double space=w1/(h.count()-1);
    QVector<QLine> lines;
    QPen pen1;
    pen1.setColor(QColor(133, 159, 255));
    pen1.setWidth(2);
    pen1.setStyle(Qt::SolidLine);
    painter.setPen(pen1);

    painter.setBrush(QBrush(QColor(243, 246, 255)));
    double h1=(height()-20)/(max-min);//每一小块的长度
    painter.translate(0,height()-10-10);

    for(int i=0;i<h.count()-1;++i)
    {
        double y1,y2;
        y1=(h.at(i)-min)*h1;//高度
        y2=(h.at(i+1)-min)*h1;//高度
        lines.append(QLine(x1,-y1,x1+space,-y2));
        x1+=space;
    }
    painter.drawLines(lines);
    painter.restore();

}

窗体控件透明度

QT 窗体控件的透明度设置（三种方法）_qt paint setbrush 透明_chenyazhou88的博客-CSDN博客

    opacityEffect=new QGraphicsOpacityEffect(this);
    this->setGraphicsEffect(opacityEffect);
    opacityEffect->setOpacity(0.2);

自定义按钮

#ifndef BTN5_H
#define BTN5_H

#include <QPushButton>
#include "btn1.h"
class btn5 : public btn1
{
    Q_OBJECT
public:
    btn5(QWidget * parent = nullptr);
    void set_normal_icon(QString icon);
    void init(QSize size,QSize hover_size);
protected:
    void paintEvent(QPaintEvent *) override;
    void enterEvent(QEvent *event) override;
    void leaveEvent(QEvent *event) override;
private:
    QString normal_icon;
    QSize icon_size,size,hover_size;
    bool hover;
signals:
    void mouse_enter();
    void mouse_leave();
};

#endif // BTN5_H

#include "btn5.h"
#include <QDebug>
#include <QPainter>
#pragma execution_character_set("utf-8")
#pragma execution_character_set("utf-8")
btn5::btn5(QWidget * parent ): btn1(parent)
{
    init(QSize(50,50),QSize(150,50));
    icon_size=QSize(25,25);
}

void btn5::set_normal_icon(QString icon)
{
    normal_icon=icon;
}

void btn5::init(QSize s,QSize hover_s)
{
    size=s;
    hover_size=hover_s;
    QSizePolicy sizePolicy1(QSizePolicy::Fixed, QSizePolicy::Fixed);
    sizePolicy1.setHorizontalStretch(0);
    sizePolicy1.setVerticalStretch(0);
    sizePolicy1.setHeightForWidth(this->sizePolicy().hasHeightForWidth());
    this->setSizePolicy(sizePolicy1);
    //宽高
    this->setMinimumSize(size);
    this->setMaximumSize(size);

    hover=false;
}


void btn5::enterEvent(QEvent *event)
{
    Q_UNUSED(event);
    qDebug()<<"进入事件发生";
    hover=true;
    //显示
}

void btn5::leaveEvent(QEvent *event)
{
    Q_UNUSED(event);
    qDebug()<<"离开事件发生";
    hover=false;
    //隐藏
}

void btn5::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform | QPainter::TextAntialiasing, true);

    QPen pen;
    pen.setColor(QColor(230,230,230));
    pen.setStyle(Qt::SolidLine);
    pen.setWidth(1);
    //透明背景
    painter.save();
    painter.setPen(Qt::NoPen);
    painter.setBrush(QBrush(QColor(255,255,255,0)));
    painter.drawRect(rect());
    painter.restore();

    if(!hover){
        this->setMinimumSize(size);
        this->setMaximumSize(size);
        painter.save();
        //画圆角矩形
        painter.setPen(pen);
        painter.setBrush(QBrush(QColor(255,255,255)));
        double side=qMin(width(),height());
        painter.drawRoundedRect(rect(),side/2,side/2,Qt::AbsoluteSize);
        painter.restore();

        painter.save();
        //画图标
        QPixmap pix(normal_icon);
        pix=pix.scaled(icon_size,Qt::IgnoreAspectRatio);
        painter.translate(width()/2,height()/2);
        QRectF target(-icon_size.width()/2,-icon_size.height()/2,icon_size.width(),icon_size.height());
        QRectF source(0,0,icon_size.width(),icon_size.height());
        painter.drawPixmap(target,pix,source);

        painter.restore();
    }
    else{
        this->setMinimumSize(hover_size);
        this->setMaximumSize(hover_size);

        painter.save();
        //画圆角矩形


        painter.setPen(pen);
        painter.setBrush(QBrush(QColor(255,255,255)));
        double side=qMin(width(),height());
        painter.drawRoundedRect(rect(),side/2,side/2,Qt::AbsoluteSize);
        painter.restore();

        painter.save();
        //画图标
        QPixmap pix(normal_icon);
        pix=pix.scaled(icon_size,Qt::IgnoreAspectRatio);
        //图标所占宽度：与之前一样
        painter.translate(size.width()/2,height()/2);
        QRectF target(-icon_size.width()/2,-icon_size.height()/2,icon_size.width(),icon_size.height());
        QRectF source(0,0,icon_size.width(),icon_size.height());
        painter.drawPixmap(target,pix,source);

        painter.restore();

        //画文字
        painter.save();
        painter.translate(size.width(),height()/2);
        QFont font;
        font.setPointSize(10);
        painter.setFont(font);
        QPen pen;
        pen.setColor(QColor(50,50,50));
        painter.setPen(pen);
        painter.drawText(0,-height()/2,hover_size.width()-size.width(),height(),Qt::AlignLeft | Qt::AlignVCenter,text());
        painter.restore();
    }
}

 阶段性效果图：