旋转后QGraphicsSvgItem定位 [英] QGraphicsSvgItem positioning after rotation

问题描述

当我尝试旋转QGraphicsSvgItem对象并设置位置时，遇到了一个奇怪的问题/功能.

I encountered a strange issue/feature when I try to rotate a QGraphicsSvgItem object and set a position.

检查以下示例: 为了简单起见，我有一个.svg，它是一个蓝色矩形.我使用该文件创建了两个QGraphicsSvgItem，并将它们旋转90度.我将它们都设置在相同的位置，但是旋转的一个被错误地"定位(也许这是正确的行为).看起来x，y坐标(左上角)现在是右上角，仍然像没有旋转一样.从我的角度来看，这看起来很奇怪，我希望当我旋转并设置位置时，形状的第一个点"应该位于形状开始"的位置.

Check the following example: I have one .svg for the sake of simplicity that is a blue rectangle. I create two QGraphicsSvgItem using the file and I rotate on of them with 90 degree. I set both of them to the same position, however the rotated one positioned 'wrongly'(maybe that is the correct behaviour). It looks like that the x,y coordinate(top-left corner) is now the top-right corner, remains like that it is not rotated. It looks strange from my viewpoint, I expect that when I rotate and set the position the 'first point' of the shape should be where the shape 'starts'.

我希望上面编写的源代码更易理解:

I hope with the source code is more understandable that I wrote above:

    SVGDom *bubbleDom = shadowgram->bubble();
    _bubble = new DrawableSvgItem(sh->message(), bubbleDom->byteArray());
    this->addItem(_bubble);
    _bubble->setPos((this->width()-_bubble->sceneBoundingRect().width()) / 2, (this->height() - _bubble->sceneBoundingRect().height()) / 2);
    qDebug() <<"Bubble pos: " << _bubble->pos();
    qDebug() <<"Bubble boundindRect: " << _bubble->boundingRect();
    qDebug() << "Bubble rect: " <<_bubble->sceneBoundingRect();
    qDebug() << "Bubble topleft: " <<_bubble->sceneBoundingRect().topLeft();

    DrawableSvgItem *bubble2 = new DrawableSvgItem(sh->message(), bubbleDom->byteArray());
    this->addItem(bubble2);
    bubble2->setRotation(90);
    bubble2->setPos(_bubble->pos());
    qDebug() << "Bubble2 pos: " << bubble2->pos();
    qDebug() <<"Bubble2 boundindRect: " << bubble2->boundingRect();
    qDebug() << "Bubble2 rect: " <<bubble2->sceneBoundingRect();
    qDebug() <<"Bubble2 topleft: " << bubble2->sceneBoundingRect().topLeft();

DrawableSvgItem只是QGraphicsSvgItem的扩展，我创建了QGraphicsSvgItem以便将源路径绘制到该项中.目前我没有使用它.

DrawableSvgItem is only an extension of QGraphicsSvgItem, I created for drawing sourcepaths into the item. Currently I am not using it.

输出:

Bubble pos:  QPointF(413.5, 297)
Bubble boundindRect:  QRectF(0,0 171x117)
Bubble rect:  QRectF(296.5,297 117x171)
Bubble topleft:  QPointF(296.5, 297)
Bubble2 pos:  QPointF(413.5, 297)
Bubble2 boundindRect:  QRectF(0,0 171x117)
Bubble2 rect:  QRectF(411.458,297 173.016x119.967)
Bubble2 topleft:  QPointF(411.458, 297)

在图片中，我期望以下内容:

In pictures, I expect the following:

但是我得到了以下图像:

But I got the following image:

我在此处发现了类似的问题.

I found a similar problem here.

推荐答案

bubble2围绕其变换原点旋转.默认情况下，气泡2的坐标为0,0.另外，bubble2->setPos()将此点设置为_bubble的0,0，因此您只需将bubble2->setPos()调整为所需的位置.您可以通过setTransformOriginPoint()更改变换原点.

bubble2 is rotated around its transform origin point. That is by default 0,0 in the coordinates of bubble2. Additionally bubble2->setPos() sets this point to the 0,0 of _bubble, so you only need to adjust bubble2->setPos() to the wanted pos. You can change the transform origin point by setTransformOriginPoint().

修改5.11.2014:

edit 5.11.2014:

bubble2的左上角是在bubble2坐标中定义的.这些坐标不会通过项转换来更改，旋转后，项的左上角与以前相同.这一点由setPos()放置.因此，图2显示了正确的行为.您要放置在bubble(x，y)上的角是bubble2的左下角.要获得图片1，您只需在代码中添加1行: 要么将气泡2的最后一步向右移动

Top-left of bubble2 is defined in bubble2-coordinates. These coordinates are not changed by items transformations, after rotation the top-left corner of the item is the same corner as before. This point is placed by setPos(). So picture 2 shows the correct behaviour. The corner, you want to place on bubble(x,y), is bubble2's bottom-left corner. To get picture 1 you only need to add 1 line to your code: either move bubble2 in last step by its height to the right

bubble2->setpos(413.5 + 117, 297)

或首先将气泡2的转换原点设置到底部左角

or as first step set transformation origin point of bubble2 to bottem left corner

bubble2->setTransformOriginPoint(0,117)

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