ffmpeg播放器实战（视频播放ui）

Display::Display(QWidget *parent)
    : QWidget{parent}
{
    mWidth  = 16;
    mHeight = 9;

    mVideo = new QWidget(this);
    //使用setAutoFillBackground函数可以启用或禁用自动填充背景的功能
    mVideo->setAutoFillBackground(true);
    //Qt::WA_StyledBackground是一个用于启用QWidget的样式背景的属性
    mVideo->setAttribute(Qt::WA_StyledBackground);
    mVideo->setStyleSheet("background-color: black;");

    this->setAutoFillBackground(true);
    this->setAttribute(Qt::WA_StyledBackground);
    this->setStyleSheet("background-color: black;");
}
Display::~Display()
{
    delete mVideo;
}

void Display::resizeEvent(QResizeEvent* event)
{
    setWidgetSize();
    QWidget::resizeEvent(event);
}

void Display::setWidgetSize()
{
    int widgetWidth  = this->width();
    int widgetHeight = this->height();

    /*
     *   宽比     宽度
     *   ——   =  ——
     *   高比     高度
     *
     *  根据宽度得到高度
     *
     *  如果得到高度大于实际高度
     *
     *  则：
     *
     *  根据高度得到宽度
     *
     */
    int tempWidth    = widgetWidth;
    int tempHeight   = tempWidth * this->mHeight / this->mWidth;
    if (tempHeight > widgetHeight) {
        tempHeight = widgetHeight;
        tempWidth  = tempHeight * this->mWidth / this->mHeight;
    }
    //如果计算出来在波动范围内则不动
    if (tempWidth >= widgetWidth - 1 && tempWidth <= widgetWidth + 1 && tempHeight >= widgetHeight - 1 && tempHeight <= widgetHeight + 1)
        return;
    mVideo->setGeometry((widgetWidth - tempWidth) / 2, (widgetHeight - tempHeight) / 2, tempWidth, tempHeight);
}
void Display::setNewSize(int width, int height)
{
    mWidth  = width;
    mHeight = height;
    setWidgetSize();
}

QWidget* Display::getVideo()
{
    return mVideo;
}