QFontInfo::Qt 4和Qt 5之间的pixelSize()更改

此代码:

QFont convertPointToPixelSize( const QFont& f )
{
    QFont ret( f );
    QFontInfo fi( ret );
    ret.setPixelSize( fi.pixelSize() );
    return ret;
}
qDebug() << "getFont()=" << getFont();
qDebug() << "convertPointToPixelSize( getFont() )=" << convertPointToPixelSize( getFont());

getFont()= QFont( "MS Shell Dlg 2,36,-1,5,50,0,0,0,0,0" ) 
convertPointToPixelSize( getFont() )= QFont( "MS Shell Dlg 2,-1,48,5,50,0,0,0,0,0" ) 
getFont()= QFont( "Arial,28,-1,5,50,0,0,0,0,0" ) 
convertPointToPixelSize( getFont() )= QFont( "Arial,-1,37,5,50,0,0,0,0,0" ) 
getFont()= QFont( "Times New Roman,72,-1,5,50,0,0,0,0,0" ) 
convertPointToPixelSize( getFont() )= QFont( "Times New Roman,-1,96,5,50,0,0,0,0,0" )

在Qt 5.11.1上:

getFont()= QFont( "MS Shell Dlg 2,36,-1,5,50,0,0,0,0,0" )
convertPointToPixelSize( getFont() )= QFont( "MS Shell Dlg 2,-1,72,5,50,0,0,0,0,0" )
getFont()= QFont( "Arial,28,-1,5,50,0,0,0,0,0" )
convertPointToPixelSize( getFont() )= QFont( "Arial,-1,56,5,50,0,0,0,0,0" )
getFont()= QFont( "Times New Roman,72,-1,5,50,0,0,0,0,0" )
convertPointToPixelSize( getFont() )= QFont( "Times New Roman,-1,144,5,50,0,0,0,0,0" )

请注意,对于相同的字体,返回的QFontInfo::pixelSize()值不同。因此QFontInfo::pixelSize()似乎在Qt 4和Qt 5之间发生了变化(为qt5返回更大的值)。我可以做些什么来获取Qt 5中Qt 4的QFontInfo::pixelSize()值吗?我看了QFontMetrics,但没有看到任何有用的东西。