学说查询不同的相关实体(Doctrine query distinct related entity)

 在哪里实例化QPen并不重要。 
 
 QPen的默认宽度为0.这是一个特殊的值，这意味着化妆品是真实的，宽度实际上是1.所以，如果你不想让笔化妆，你必须将其设置为所需的宽度。 您可能还需要将化妆品设置为假。 
 
 这是一个简单的例子： 
 
#include <QtGui>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QGraphicsView view;
    QGraphicsScene scene;

    QGraphicsRectItem *item1 = scene.addRect(20, 20, 20, 20);
    QGraphicsRectItem *item2 = scene.addRect(50, 20, 20, 20);

    QPen pen1, pen2;
    pen1.setWidth(5);
    pen2.setWidth(5);
    pen1.setCosmetic(true);
    pen2.setCosmetic(false);

    item1->setPen(pen1);
    item2->setPen(pen2);

    view.setScene(&scene);
    view.scale(4, 4); // both rects are the same size, but one a has wider pen
    view.show();

    return a.exec();
}

It doesn't really matter where you instantiate the QPen.
 
QPen has a default width of 0. This is a special value that means cosmetic is true and the width is actually 1. So if you don't want the pen to be cosmetic you have to set it to the desired width. You might also need to set cosmetic to false.
 
Here is a simple example:
 
#include <QtGui>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QGraphicsView view;
    QGraphicsScene scene;

    QGraphicsRectItem *item1 = scene.addRect(20, 20, 20, 20);
    QGraphicsRectItem *item2 = scene.addRect(50, 20, 20, 20);

    QPen pen1, pen2;
    pen1.setWidth(5);
    pen2.setWidth(5);
    pen1.setCosmetic(true);
    pen2.setCosmetic(false);

    item1->setPen(pen1);
    item2->setPen(pen2);

    view.setScene(&scene);
    view.scale(4, 4); // both rects are the same size, but one a has wider pen
    view.show();

    return a.exec();
}