QGraphicsItem ->;得到正确的边界矩形

发布于 2024-11-15 14:15:46 字数 823 浏览 3 评论 0 原文

我正在尝试 OpenGL ES 2.0 的 hello 三角形示例。我正在使用 Qt，因此我创建了一个 QGraphicsScene 并将该代码添加为 QGraphicsItem。它绘制正确，但我无法正确获取边界矩形。三角形顶点是

GLfloat afVertices[] = 
{-0.4f,-0.4f,0.0f, 
 0.4f ,-0.4f,0.0f,
 0.0f ,0.4f ,0.0f};

，我的视口是 glViewport(0, 0, 800, 480);

正确的边界矩形坐标是什么？

我将视口设置为 QGLWidget。 QGraphicsItem 的问题是我必须重新实现该项目的边界矩形，如果我只是使用

QRectF myGraphicsItem::boundingRect() const
{

   return QGraphicsItem::boundingRect();
}

它，就会显示 对 `QGraphicsItem::boundingRect() const' 的未定义引用

我最初使用过

QRectF myGraphicsItem::boundingRect() const
{
  return QRectF(-0.4, -0.4, 0.8, 0.8);
}

，但是结果是一个非常小的边界框。当我通过反复试验使用像 QRectf(300, 200, 200, 200) 这样的值时创建了看似正确的值 - 这太“手动” - 所以我想知道也许有一些我不知道的一种坐标对应或变换。

原文

I am trying the hello triangle example of OpenGL ES 2.0. I am using Qt, so I created a QGraphicsScene and added that code as a QGraphicsItem. It draws correctly, but I cannot get the bounding rectangle correctly. The triangle vertices are

GLfloat afVertices[] = 
{-0.4f,-0.4f,0.0f, 
 0.4f ,-0.4f,0.0f,
 0.0f ,0.4f ,0.0f};

and my viewport is glViewport(0, 0, 800, 480);

What would be the correct bounding rect coordinates?

I set the viewport to a QGLWidget. The thing with the QGraphicsItem is that I have to re-implement the bounding rectangle of the item and if I just use

QRectF myGraphicsItem::boundingRect() const
{

   return QGraphicsItem::boundingRect();
}

it says undefined reference to `QGraphicsItem::boundingRect() const'

I had originally used

QRectF myGraphicsItem::boundingRect() const
{
  return QRectF(-0.4, -0.4, 0.8, 0.8);
}

but the result is a very small bounding box. The seemingly correct one was created when I was used values like QRectf(300, 200, 200, 200) by trial and error -which is too 'manual'-, so I was wondering maybe there is some kind of coordinate correspondence or transformation that I'm unaware of.

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太阳男子 2024-11-22 14:15:46

QGraphicsItem::boundingRect() 是一个纯虚函数。因此，没有实施。您必须提供自己的实现。根据你的顶点，可能

QRectF myGraphicsItem::boundingRect() const
{
  return QRectF(-0.4, -0.4, 0.8, 0.8);
}

QGraphicsItem::boundingRect() is a pure virtual function. Thus, there is no implementation. You must provide your own implementation. Based upon your vertices, probably

QRectF myGraphicsItem::boundingRect() const
{
  return QRectF(-0.4, -0.4, 0.8, 0.8);
}

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空心空情空意 2024-11-22 14:15:46

我不确定我是否遵循，如果您使用 QGraphicsItem（带或不带 OpenGL 视口），您通常会使用 QGraphicsItem::boundingRect() 获取边界矩形？

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春花秋月 2024-11-22 14:15:46

我会这样做（用Python）：

# inside class
   def parentBoundingRect(self):
      return self.mapToParent(self.boundingRect()).boundingRect()

# or if that doesn't work
   def parentBoundingRect(self):
      pos = self.pos()
      rect = self.transform().mapToPolygon(self.boundingRect()).boundingRect()
      return QRectF(pos.x(), pos.y(), rect.width(), rect.height())

# or if that doesn't work, keep playing with it til it does! :)

I would do (in Python):

# inside class
   def parentBoundingRect(self):
      return self.mapToParent(self.boundingRect()).boundingRect()

# or if that doesn't work
   def parentBoundingRect(self):
      pos = self.pos()
      rect = self.transform().mapToPolygon(self.boundingRect()).boundingRect()
      return QRectF(pos.x(), pos.y(), rect.width(), rect.height())

# or if that doesn't work, keep playing with it til it does! :)

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